Joined body, joining sheet, and method for producing joined body

Abstract

Provided is a joined body that has a configuration in which an upper metal-containing member 2 and a lower metal-containing member 3 are joined on the obverse and reverse sides of a joining sheet 1, and is capable of suppressing cracking and deformation of the joining sheet 1 even when stress is applied to the joining sheet 1 due to an expansion rate difference, and the like, between members caused by a temperature change.　The joined body is characterized in that: each of the upper metal-containing member 2 and the lower metal-containing member 3 is provided with a metal part on a surface to which the joining sheet 1 is joined; the joining sheet 1 is a cured product of a thermosetting resin composition containing a thermosetting resin and an inorganic filler; the entire upper surface of the joining sheet 1 is joined to the upper metal-containing member 2, and the entire lower surface of the joining sheet 1 is joined to the lower metal-containing member 3; and in the case where the joining sheet 1 is viewed in a cross section, when P1A represents the resin area percentage in end regions 1A from either one of the right and left side ends of the joining sheet 1 to a point 300 μm inward thereof, and when P1B represents the resin area percentage in a central region 1B other than the end regions 1A, the value of P1A / P1B is larger than 1.10.

Description

Joint body, joint sheet, and method for manufacturing joint body

[0001] The present invention relates to a bonded body having a configuration in which an upper metal-containing member and a lower metal-containing member are bonded to the front and back of a bonding sheet, such as a power semiconductor device, a bonding sheet used therefor, and a method for manufacturing the bonded body.

[0002] Among devices using semiconductors, devices that control or convert power such as from a power supply are called "power semiconductor devices." Known power semiconductor devices equipped with electronic components include an insulating substrate on the top surface of a metal base plate (heat sink), on which electronic components such as semiconductor elements are placed, and a metal or other heat sink is placed on top of the electronic components, and these electronic components and heat sink are enclosed and sealed with a synthetic resin (see Patent Documents 1 to 4).

[0003] As the insulating substrate, ceramic substrates with high thermal conductivity, such as alumina substrates and aluminum nitride substrates, have traditionally been used because they can provide both thermal conductivity and insulation. However, ceramic substrates have problems such as being easily cracked by impact and being difficult to make thin and compact. Therefore, thermally conductive sheets made of thermosetting resins such as epoxy resins and inorganic fillers have been proposed as insulating substrates.

[0004] Regarding sheets using a thermosetting resin and an inorganic filler, for example, Patent Document 5 discloses a sealing resin sheet that contains alumina particles and boron nitride together with a thermosetting resin and a thermoplastic resin, and has a thermal conductivity of 3 W / m·K or more in the sheet thickness direction after thermal curing. Also, Patent Document 6 proposes a heat-dissipating resin sheet that contains an epoxy resin with a Tg of 60° C. or less and boron nitride, and the content of boron nitride is 30% by volume or more and 60% by volume or less.

[0005] JP 2000-323593 A JP 2004-103846 A WO 2016 / 162991 A JP 2018-74089 A JP 2017-036415 A WO 2019 / 189746 A

[0006] As shown in Figure 1, in a bonded structure having a configuration in which an upper metal-containing member 2 and a lower metal-containing member 3 are bonded to the front and back of a bonding sheet 1 (corresponding to the insulating substrate), it has been found that when stress is applied to the bonding sheet 1 due to differences in expansion coefficients between the members caused by temperature changes, pressure is concentrated locally at the edge of the bonding sheet 1, causing cracks and deformation within the bonding sheet 1.

[0007] Therefore, the object of the present invention is to provide a new joined body having a configuration in which an upper metal-containing member 2 and a lower metal-containing member 3 are joined to the front and back of a joining sheet 1, which can suppress cracking and deformation in the joining sheet 1 even if stress is applied to the joining sheet 1 due to differences in expansion coefficients between the members caused by temperature changes, a joining sheet to be used therefor, and a method for manufacturing the joined body.

[0008] The bonded structure proposed by the present invention, the bonding sheet used therein, and the method for manufacturing the bonded structure have the following configurations in order to solve the above problems.

[0009] [1] A first aspect of the present invention is a joined body having a configuration in which an upper metal-containing member 2 and a lower metal-containing member 3 are joined to the front and back of a joining sheet 1, wherein the upper metal-containing member 2 and the lower metal-containing member 3 each have a metal portion on the joining surface with the joining sheet 1, the joining sheet 1 is a cured product of a thermosetting resin composition containing a thermosetting resin and an inorganic filler, the entire upper surface of the joining sheet 1 is joined to the upper metal-containing member 2, and the entire lower surface of the joining sheet 1 is joined to the lower metal-containing member 3, and when the joining sheet 1 is viewed in cross section, the resin area ratio in an end region 1A extending from one of the left and right end portions of the joining sheet 1 to 300 μm inward is P １Ａ , the resin area ratio in the central region 1B other than the end region 1A is P １Ｂ When P １Ａ / P １Ｂ The bonded body is characterized in that the value of is greater than 1.10.

[0010] [2] A second aspect of the present invention is a joined body having a configuration in which an upper metal-containing member 2 and a lower metal-containing member 3 are joined to the front and back of a joining sheet 1, wherein the upper metal-containing member 2 and the lower metal-containing member 3 each have a metal portion on the joining surface with the joining sheet 1, the joining sheet 1 is a cured product of a thermosetting resin composition containing a thermosetting resin and an inorganic filler, the entire upper surface of the joining sheet 1 is joined to the upper metal-containing member 2, and the entire lower surface of the joining sheet 1 is joined to the lower metal-containing member 3, and when the joining sheet 1 is viewed in cross section, the void area ratio in an end region 1A extending from one of the left and right end portions of the joining sheet 1 to 300 μm inward is S １Ａ , the void area ratio in the central region 1B other than the end region 1A is S １Ｂ When this is done, S １Ａ / S １Ｂ The bonded body is characterized in that the value of is greater than 1.

[0011] [3] A third aspect of the present invention is a joined body having a configuration in which an upper metal-containing member 2 and a lower metal-containing member 3 are joined to the front and back of a joining sheet 1, wherein the upper metal-containing member 2 and the lower metal-containing member 3 each have a metal portion on the joining surface with the joining sheet 1, the joining sheet 1 is a cured product of a thermosetting resin composition containing a thermosetting resin and an inorganic filler, the entire upper surface of the joining sheet 1 is joined to the upper metal-containing member 2, and the entire lower surface of the joining sheet 1 is joined to the lower metal-containing member 3, and when the joining sheet 1 is viewed in cross section, the average void size in an end region 1A extending from one of the left and right end portions of the joining sheet 1 to 300 μm inward is L １Ａ , the average void size in the central region 1B other than the end region 1A is L １Ｂ When this is done, L １Ａ / L １Ｂ The bonded body is characterized in that the value of is greater than 2.

[0012] [4] A fourth aspect of the present invention is a joined body having a configuration in which the joining sheet 1 and the upper metal-containing member 2 are directly joined together, and the joining sheet 1 and the lower metal-containing member 3 are directly joined together in any one of the first to third aspects. [5] A fifth aspect of the present invention is a joined body having a configuration in which the upper metal-containing member 2 is joined to the joining sheet 1, with the lower surface of the sheet- or plate-shaped metal portion 25 exposed at the joining surface with the joining sheet 1, and the metal portion 25 is covered and sealed with resin 26. [6] A sixth aspect of the present invention is a joined body having a plate- or sheet-shaped metal portion 3 at the joining surface with the joining sheet 1 in any one of the first to fifth aspects.

[0013] [7] A seventh aspect of the present invention is the joined body of any one of the first to sixth aspects, characterized in that the thermal conductivity in the thickness direction of the joining sheet 1 is 10 W / m K or more. [8] An eighth aspect of the present invention is the joined body of any one of the first to seventh aspects, characterized in that the breakdown voltage of the joining sheet 1 is 5 kV or more.

[0014] [9] A ninth aspect of the present invention is the joined body of any one of the first to eighth aspects, wherein the metal portions of the upper metal-containing member 2 and the lower metal-containing member 3 are made of a material containing copper or aluminum.

[10] A tenth aspect of the present invention is the joined body of any one of the first to ninth aspects, wherein the inorganic filler contained in the joining sheet 1 contains boron nitride agglomerated particles.

[11] A eleventh aspect of the present invention is the joined body of the tenth aspect, wherein the boron nitride agglomerated particles have a house-of-card structure.

[12] A twelfth aspect of the present invention is the joined body of any one of the first to eleventh aspects, wherein the thermosetting resin contained in the joining sheet 1 contains an epoxy resin.

[13] A thirteenth aspect of the present invention is the joined body of any one of the first to twelfth aspects, wherein the thickness of the joining sheet 1 is 80 μm or more and 300 μm or less.

[0015]

[14] A fourteenth aspect of the present invention is a joining sheet which is a cured product of a thermosetting resin composition containing a thermosetting resin and an inorganic filler, and when the joining sheet 1 is viewed in cross section, the resin area ratio in an end region 1A extending from one side end of the joining sheet 1 to an inner 300 μm is P １Ａ , the resin area ratio in the central region 1B other than the end region 1A is P １Ｂ When P １Ａ / P １Ｂ When the joining sheet 1 is viewed in cross section, the void area ratio in the edge region 1A extending from the left or right edge of the joining sheet 1 to the inside 300 μm is S １Ａ , the void area ratio in the central region 1B other than the end region 1A is S １Ｂ When this is done, S １Ａ / S １Ｂ The value of is greater than 1, and when the joining sheet 1 is viewed in cross section, the average void size in the edge region 1A extending from the left or right edge of the joining sheet 1 to 300 μm inside is L １Ａ , the average void size in the central region 1B other than the end region 1A is L １Ｂ When this is done, L １Ａ / L １Ｂ The bonding sheet is characterized by satisfying at least one of the following conditions:

[0016]

[15] A fifteenth aspect of the present invention is the method for producing a joined body according to any one of the first to thirteenth aspects, characterized in that a thermosetting sheet obtained by molding the thermosetting resin composition into a sheet is placed on a lower metal-containing member 3, uniform pressure is applied to bond the lower metal-containing member 3 and the thermosetting sheet together, and then an upper metal-containing member 2 is placed on the thermosetting sheet and uniform pressure is applied to bond the thermosetting sheet and the upper metal-containing member 2 together.

[16] A sixteenth aspect of the present invention is the method for producing a joined body according to the fifteenth aspect, wherein the thermosetting sheet is subjected to low-temperature aging in an environment of −50° C. or higher and 0° C. or lower before being placed on the lower metal-containing member 3.

[0017] The bonded structure proposed by the present invention is a bonded structure having a configuration in which an upper metal-containing member 2 and a lower metal-containing member 3 are bonded to the front and back of a bonding sheet 1, and the resin area ratio in an end region 1A extending from one side end of the bonding sheet 1 to the inside by 300 μm is set to P １Ａ , the resin area ratio in the central region 1B other than the end region 1A is P １Ｂ When P １Ａ / P １Ｂ The value of is made larger than 1.10, or the void area ratio in the end region 1A is made smaller than S １Ａ , the void area ratio in the central region 1B other than the end region 1A is S １Ｂ When this is done, S １Ａ / S １Ｂ The value of is made larger than 1, or the average void size in the edge region 1A from the left or right side edge of the bonding sheet 1 to the inside 300 μm is made smaller than L １Ａ , the average void size in the central region 1B other than the end region 1A is L １Ｂ When this is done, L １Ａ / L １Ｂ By making the value of σ larger than 2, cracks and deformations in the bonding sheet 1 can be suppressed even if stress is applied to the bonding sheet 1 due to differences in expansion coefficients between members caused by temperature changes.

[0018] 1 is a cross-sectional view (in the thickness direction) of a bonded body as one example of the present invention; FIG. 2 is a cross-sectional view (in the thickness direction) of a bonded body as another example of the present invention; FIG. 3 is a cross-sectional view (in the thickness direction) of a bonded body as another example of the present invention; FIG. 4 is a cross-sectional view (in the thickness direction) of a bonded body as another example of the present invention; FIG. 5 is a cross-sectional view (in the thickness direction) of a bonded body as another example of the present invention; FIG. 6 is a cross-sectional view (in the thickness direction) of a bonded body as yet another example of the present invention; FIG. 7 is a cross-sectional view (in the thickness direction) of a bonded body as yet another example of the present invention; FIG. 8 is a cross-sectional view (in the thickness direction) of a bonded body as yet another example of the present invention;

[0019] An example of an embodiment of the present invention will be described below, but the present invention is not limited to the embodiment described below.

[0020] <<Jointed Body I of the Present Invention>> A joined body according to one embodiment of the present invention (also referred to as "jointed body I of the present invention") is a joined body having a configuration in which an upper metal-containing member 2 and a lower metal-containing member 3 are joined to the front and back of a joining sheet 1, as shown in FIG. 1. That is, it is a joined body having a configuration in which the upper metal-containing member 2 is joined to the upper surface of the joining sheet 1, and the lower metal-containing member 3 is joined to the lower surface of the joining sheet 1. In this case, it is preferable that the joining sheet 1 and the upper metal-containing member 2 are directly joined, and that the joining sheet 1 and the lower metal-containing member 3 are directly joined. "Direct joining" means that the joining is performed without the interposition of any other member, and does not involve the use of an adhesive (including solder). However, if the joining surfaces of the joining sheet 1, the upper metal-containing member 2, and the lower metal-containing member 3 have been subjected to a thin-layer surface treatment such as plating treatment such as nickel plating or tin plating, chemical conversion treatment, or physical treatment, as described below, this is considered to be "direct joining."

[0021] 1 , when viewed in cross section in the thickness direction, the present invention joined body I has only to have one entire surface of the joining sheet 1, i.e., the entire upper surface, joined to the upper metal-containing member 2, and the other entire surface of the joining sheet 1, i.e., the entire lower surface, joined to the lower metal-containing member 3. Therefore, the area of ​​the upper surface of the joining sheet 1 needs to be the same as or smaller than the area of ​​the lower surface of the upper metal-containing member 2, and the area of ​​the lower surface of the joining sheet 1 needs to be the same as or smaller than the area of ​​the upper surface of the lower metal-containing member 3. In this case, the area of ​​the upper surface of the joining sheet 1 is preferably 80% or more and 100% or less of the area of ​​the lower surface of the upper metal-containing member 2 (100%), and more preferably 90% or more and 100% or less.

[0022] Furthermore, it is preferable that the upper surface of the lower metal-containing member 3 is larger than the lower surface of the upper metal-containing member 2. A single or multiple upper metal-containing members 2 can be placed on the lower metal-containing member 3 via multiple bonding sheets 1. Note that the bonding surfaces of the bonding sheet 1, upper metal-containing member 2, and lower metal-containing member 3 may each be flat, as shown in Fig. 1. However, each bonding surface may have a concave or convex portion.

[0023] (Resin Area Ratio) When the joining sheet 1 is viewed in cross section, the resin area ratio in the edge region 1A extending from one side edge of the joining sheet 1 to the inner side by 300 μm is P １Ａ , the resin area ratio in the central region 1B other than the end region 1A is P １Ｂ When P １Ａ / P １Ｂ It is preferred that the value of is greater than 1.10.

[0024] In the present invention, the "cross section" of "when the bonding sheet 1 is viewed in cross section" refers to a cross section showing the inner position and area from one of the left and right side ends of the bonding sheet 1, and refers to a cross section cut in the thickness direction along the length or width direction of the bonding sheet 1.

[0025] Resin area ratio P in end region 1A １Ａ That is, the resin ratio is the resin area ratio P １Ｂ By making it larger than the ratio of the two (P １Ａ / P １Ｂ By making the value of ) larger than 1.10, even if stress is applied to the joining sheet 1 due to a difference in the expansion coefficient between the members caused by a temperature change, cracks and deformations in the joining sheet 1 can be suppressed. From this point of view, the resin area ratio in the end region 1A extending from one of the left and right end portions of the joining sheet 1 to 300 μm inside can be set to P １Ａ , the resin area ratio in the central region 1B other than the end region 1A is P １Ｂ When P １Ａ / P １Ｂ The value of P is preferably larger than 1.10, more preferably 1.11 or more, even more preferably 1.12 or more, and even more preferably 1.13 or more. On the other hand, from the viewpoint of suppressing the intrusion of moisture from the atmosphere between the upper metal-containing member 2 and the lower metal-containing member 3, １Ａ / P １Ｂ The value is more preferably 2.0 or less, and more preferably 1.8 or less, and may be 1.5 or less, or may be 1.2 or less.

[0026] In the present invention, the region extending from one of the left and right end portions of the bonding sheet 1 to 300 μm inward is designated as the end region 1A because it is considered to be the necessary range for a stress relaxation portion to exhibit the effects of the present invention, such as improving the reliability of cycle tests, and is also considered to be the minimum range from the viewpoint of maintaining insulation. For example, when the thickness of the bonding sheet 1 is 80 μm to 300 μm, the range in which stress is applied can be estimated to be approximately 100 μm to 500 μm from one of the left and right end portions of the bonding sheet 1. Therefore, in the present invention, the region extending from the end portion to 300 μm inward, which is the center of the 100 μm to 500 μm range, is designated as the region in which the effect of stress can be evaluated.

[0027] To adjust the resin area ratio, i.e., resin ratio, in the edge region 1A and central region 1B of the joining sheet 1 as described above, an upper metal-containing member 2 and a lower metal-containing member 3 are placed on the front and back of the thermosetting sheet Ia, which will be described later, and the joining sheet 1 is pressed, and the thermosetting sheet Ia is thermally cured, the area ratio of the thermosetting sheet Ia to the upper metal-containing member 2, the pressing conditions, the type of thermosetting resin, the type of inorganic filler, the presence or absence and conditions of low-temperature aging, etc. may be adjusted. However, the present invention is not limited to such a method. The resin area ratio P １Ａ and P １Ｂ can be calculated by using image analysis software based on a cross-sectional photograph of each region of the bonding sheet 1 to determine the total area of ​​resin present per unit cross-sectional area of ​​the bonding sheet 1, i.e., the total resin area.

[0028] (Void Area Ratio) When the joining sheet 1 is viewed in cross section, the void area ratio in the edge region 1A extending from one side edge of the joining sheet 1 to the inner side by 300 μm is S １Ａ , the void area ratio in the central region 1B other than the end region 1A is S １Ｂ When this is done, S １Ａ / S １Ｂ It is preferable that the value of is greater than 1. The void area ratio S in the edge region 1A １Ａ is the void area ratio S in the central region 1B. １ＢBy making the void area ratio larger than S, even if stress is applied to the joining sheet 1 due to the difference in expansion coefficient between the members caused by temperature change, cracks and deformations in the joining sheet 1 can be suppressed. From this point of view, when the joining sheet 1 is viewed in cross section, the void area ratio in the end region 1A from the left or right end of the joining sheet 1 to the inside by 300 μm is set to S １Ａ , the void area ratio in the central region 1B other than the end region 1A is S １Ｂ When this is done, S １Ａ / S １Ｂ The value of S is preferably greater than 1, more preferably 2 or more, even more preferably 3 or more, even more preferably 4 or more, even more preferably 5 or more, and even more preferably 6 or more. On the other hand, from the viewpoint of suppressing the intrusion of moisture from the atmosphere between the upper metal-containing member 2 and the lower metal-containing member 3, １Ａ / S １Ｂ The value is more preferably 10 or less, and more preferably 9 or less, and may be 8 or less, or may be 7 or less.

[0029] Furthermore, the area of ​​the metal portion exposed on the lower surface of the upper metal-containing member 2 is preferably smaller than the area of ​​the joining sheet 1, and is preferably 20% to 90% of the area of ​​the joining sheet 1, and more preferably 30% or more or 80% or less. Furthermore, the area of ​​the metal portion exposed on the lower surface of the upper metal-containing member 2 is preferably 20% to 90% of the area of ​​the central region 1B of the joining sheet 1, and more preferably 30% or more or 80% or less. Furthermore, it is preferable that the entire surface of the metal portion exposed on the lower surface of the upper metal-containing member 2 is in contact with the central region 1B of the joining sheet 1. With this configuration, discharge from the end face of the joining sheet 1 can be suppressed.

[0030] To adjust the void area ratio, i.e., void ratio, in the edge region 1A and central region 1B of the joining sheet 1 as described above, an upper metal-containing member 2 and a lower metal-containing member 3 are placed on the front and back of the present thermosetting sheet Ia, which will be described later, and the joining sheet 1 is pressed, and the present thermosetting sheet Ia is thermally cured, the area ratio of the present thermosetting sheet Ia to the upper metal-containing member 2, the pressing conditions, the type of thermosetting resin, the type of inorganic filler, the presence or absence and conditions of low-temperature aging, etc. may be adjusted. However, the present invention is not limited to such a method. The above void area ratio S １Ａ and S １Ｂ can be calculated by using image analysis software based on a cross-sectional photograph of each region of the bonding sheet 1 to determine the total area of ​​voids present per unit cross-sectional area of ​​the bonding sheet 1, i.e., the total void area.

[0031] (Average Void Size) When the joining sheet 1 is viewed in cross section, the average void size in the edge region 1A extending from one side edge of the joining sheet 1 to 300 μm inside is L １Ａ , the average void size in the central region 1B other than the end region 1A is L １Ｂ When this is done, L １Ａ / L １Ｂ It is preferable that the value of is greater than 2. The average void size L in the edge region 1A １Ａ , the average void size L in the central region 1B. １Ｂ By making it larger than the ratio of the two (L １Ａ / L １Ｂ By making the value of ) larger than 2, even if stress is applied to the joining sheet 1 due to a difference in expansion coefficient between members caused by a temperature change, cracks and deformations in the joining sheet 1 can be suppressed. From this point of view, when the joining sheet 1 is viewed in cross section, the average void size in the end region 1A extending from one of the left and right end portions of the joining sheet 1 to 300 μm inward is set to L １Ａ , the average void size in the central region 1B other than the end region 1A is L １Ｂ When this is done, L １Ａ / L １ＢThe value of L is preferably greater than 2, more preferably 3 or more, more preferably 4 or more, more preferably 5 or more, more preferably 6 or more, more preferably 7 or more, and even more preferably 8 or more. On the other hand, from the viewpoint of suppressing the intrusion of moisture from the atmosphere between the upper metal-containing member 2 and the lower metal-containing member 3, １Ａ / L １Ｂ The value is more preferably 20 or less, more preferably 10 or less, and may be 9 or less.

[0032] To adjust the average void size in the edge region 1A and central region 1B of the joining sheet 1 as described above, the upper metal-containing member 2 and the lower metal-containing member 3 are placed on the front and back of the thermosetting sheet Ia described below, the joining sheet 1 is pressed, and the thermosetting sheet Ia is thermally cured. In this method, the area ratio of the thermosetting sheet Ia to the upper metal-containing member 2, the pressure conditions, the type of thermosetting resin, the type of inorganic filler, the presence or absence and conditions of low-temperature aging, etc. may be adjusted. However, the present invention is not limited to such a method. １Ａ and L １Ｂ can be calculated by determining the average area of ​​voids per number based on a cross-sectional photograph of each region of the bonding sheet 1 using image analysis software.

[0033] Furthermore, the present invention conjugate I is １Ａ / P １Ｂ The value of is greater than 1.10 and S １Ａ / S １Ｂ It is more preferable that the value of P is greater than 1. １Ａ / P １Ｂ The value of is greater than 1.10 and L １Ａ / L １Ｂ It is more preferable that the value of S is greater than 2. １Ａ / S １Ｂ The value of is greater than 1 and L １Ａ / L １Ｂ It is more preferable that the value of is greater than 2.

[0034] Furthermore, P １Ａ / P １Ｂ The value of is greater than 1.10 and S １Ａ / S １Ｂ The value of is greater than 1 and L１Ａ / L １Ｂ It is more preferable that the value is greater than 2. However, as will be described later, considering the respective action mechanisms, it is considered that the object of the present invention, that is, to suppress cracking and deformation in the bonding sheet 1, can be achieved by satisfying at least one of the conditions of the resin area ratio, the void area ratio, and the average void size.

[0035] Furthermore, the area of ​​the metal portion on the lower surface of the upper metal-containing member 2 is preferably smaller than the area of ​​the joining sheet 1, and is preferably 20% to 90% of the area of ​​the joining sheet 1, and more preferably 30% or more or 80% or less. Furthermore, the area of ​​the metal portion on the lower surface of the upper metal-containing member 2 is preferably 20% to 90% of the area of ​​the central region 1B of the joining sheet 1, and more preferably 30% or more or 80% or less. Furthermore, it is preferable that the entire surface of the metal portion on the lower surface of the upper metal-containing member 2 is in contact with the central region 1B. With this shape, discharge from the end face of the joining sheet 1 can be suppressed.

[0036] (Thermal Conductivity) When the bonded body I of the present invention is used for applications such as power semiconductor devices, industrial equipment, automotive equipment, and power generation energy, the thermal conductivity in the thickness direction of the bonding sheet 1 in the bonded body I of the present invention, i.e., the bonding sheet 1 in which both the upper metal-containing member 2 and the lower metal-containing member 3 are bonded, is preferably 10 W / m K or more, more preferably 11 W / m K or more, and even more preferably 12 W / m K or more. On the other hand, it is preferably 25 W / m K or less, and even more preferably 20 W / m K or less.

[0037] To adjust the thermal conductivity of the joining sheet 1 as described above, the upper metal-containing member 2 and the lower metal-containing member 3 are placed on the front and back of the thermosetting sheet Ia (described later), the joining sheet 1 is pressed, and the thermosetting sheet Ia is heat-cured. In this method, the pressing conditions, the type of thermosetting resin, the type of inorganic filler, and the presence and conditions of low-temperature aging can be adjusted. However, this method is not limited to this. The thermal conductivity of the joining sheet 1 in the thickness direction can be measured by the following method. For example, the thermal resistance value can be measured using a thermal resistance measuring device, and the thermal conductivity can be calculated from the slope of a graph plotting the thermal resistance value against the thickness.

[0038] (Breakdown voltage (BDV)) When the present invention joined body I is used for applications such as power semiconductor devices, industrial equipment, automotive equipment, and power generation energy, the breakdown voltage of the joining sheet 1 in the present invention joined body I, i.e., the joining sheet 1 joining both the upper metal-containing member 2 and the lower metal-containing member 3, is preferably 5 kV or more, more preferably 5.5 kV or more, and even more preferably 6 kV or more. The higher the breakdown voltage, the better, and there is no particular upper limit.

[0039] To adjust the breakdown voltage of the joining sheet 1 within the above range, the upper metal-containing member 2 and the lower metal-containing member 3 are placed on the front and back of the thermosetting sheet Ia (described later), the joining sheet 1 is pressed, and the thermosetting sheet Ia is heat-cured. In this method, the pressing conditions, the type of thermosetting resin, the type of inorganic filler, and the presence or absence and conditions of low-temperature aging can be adjusted. However, this method is not limited to this. The breakdown voltage of the joining sheet 1 can be measured by applying a voltage in the thickness direction of the joined body.

[0040] <Upper metal-containing member, lower metal-containing member> The upper metal-containing member 2 and the lower metal-containing member 3 may each have a configuration including a metal portion on the bonding surface with the bonding sheet 1. For example, the upper metal-containing member 2 and the lower metal-containing member 3 themselves may be made of a metal plate or metal sheet body as the metal portion, or may have a metal body exposed as the metal portion on the lower or upper surface of each, and the metal body covered with any material, for example, a synthetic resin. Other configurations are also possible. Furthermore, the shape and size of the upper metal-containing member 2 and the lower metal-containing member 3 are not particularly limited.

[0041] <Upper metal-containing member 2> As an example of the upper metal-containing member 2, as shown in FIG. 1, there can be mentioned one having a configuration in which the underside of a sheet or plate-shaped metal part 25 is exposed on the joining surface with the joining sheet 1, and the metal part 25 is covered and sealed with resin 26.

[0042] The metal part 25 may be in a plate-like, sheet-like, or other shape. The metal part 25 is preferably made of a material with good thermal conductivity. Among these, materials containing copper or aluminum, for example, can be used because they have good thermal conductivity and are relatively inexpensive. Furthermore, from the viewpoint of heat dissipation, the metal part 25 is more preferably made of copper. The joining surface of the metal part 25 with the joining sheet 1 and other surfaces may be subjected to a thin-layer surface treatment such as nickel plating, tin plating, or other plating treatment, chemical conversion treatment, or physical roughening treatment.

[0043] The resin 26 that seals the metal portion 25 may be, for example, an insulating resin, such as epoxy resin, vinyl chloride resin, acrylic resin, polypropylene, polyethylene, nylon, polycarbonate, phenol resin, polyarylate, benzoxazine, or isocyanate.

[0044] As shown in FIG. 2 , an example of the upper metal-containing member 2 is a module structure in which a semiconductor chip 27 is mounted on a metal portion 25 serving as a heat dissipation member, a wiring member 28 is wired on the metal portion 25, and the metal portion 25 and the semiconductor chip 27 are covered and sealed with an insulating resin 26. A more specific example of the upper metal-containing member 2 is a module having a molded and sealed structure. An example of the upper metal-containing member 2 is a module having a side dimension of greater than 10 mm and less than 150 mm. For example, a module structure in which one or more semiconductor chips 27 are mounted on the metal portion 25, a wiring member 28 is wired on the metal portion 25, and the metal portion 25 and the semiconductor chip 27 are embedded in a resin 26 such as an epoxy resin by transfer molding or compression molding can be given. For example, a TO package module manufactured by Infineon and a HybridPACK manufactured by Infineon are examples of such modules. ＴＭ Examples of such a power module include a power module for a DSC, and AIKQ120N75CP2XKSAI manufactured by Infineon, but are not limited to these.

[0045] <Lower Metal-Containing Member 3> An example of the lower metal-containing member 3 is one having a flat or sheet-like metal body on the joining surface with the joining sheet 1. Examples of the flat or sheet-like metal body include those made of a material containing copper or aluminum. More specifically, examples include metal plates containing copper, aluminum, or the like.

[0046] An example of the lower metal-containing member 3 is one equipped with a metal plate having a thickness of 1 mm or more. The metal plate may have an uneven structure on the joining surface of the joining sheet 1, the opposite surface, or both surfaces. The uneven structure may be a pin structure or a plate-like structure. Alternatively, the metal plate may be warped. Furthermore, the joining surface of the joining sheet 1, the opposite surface, or both surfaces of the metal plate may be subjected to a surface treatment such as nickel plating, tin plating, chemical conversion treatment, or physical roughening treatment. The metal plate may be, for example, a commonly-known cooling base plate, a cooling fin such as a pin fin, or a cooling unit. Conventionally known components can be used. Among these, pin fins are preferred.

[0047] <Bonding Sheet 1> The bonding sheet 1 contains a thermosetting resin and an inorganic filler 14, and has voids 15 inside.

[0048] The bonding sheet 1 is a cured product of a thermosetting resin composition (referred to as "the present thermosetting resin composition Ib") containing a thermosetting resin and an inorganic filler. That is, the bonding sheet 1 is a cured product of a thermosetting sheet (referred to as "the present thermosetting sheet Ia") obtained by molding the present thermosetting resin composition Ib into a sheet shape.

[0049] In the present invention, the term "thermosetting resin composition" refers to a resin composition that has the property of being cured by heat. That is, any resin composition that has the curability to be cured by heat may be used. The resin composition may be one that has already been cured to a state where there is still room for curing (also referred to as "pre-cured"), or one that has not yet been cured at all (referred to as "uncured"). Furthermore, the term "thermosetting sheet" refers to a sheet that has the property of being cured by heat. That is, any resin composition that has the curability to be cured by heat may be used. The resin composition may be one that has already been cured to a state where there is still room for curing (also referred to as "pre-cured"), or one that has not yet been cured at all (referred to as "uncured").

[0050] (Thickness) The thickness of the bonding sheet 1 is not particularly limited. When the bonded body I of the present invention is used, for example, in power semiconductor devices, industrial equipment, automotive equipment, power generation energy, etc., the thickness of the bonding sheet 1 is preferably 80 μm or more, more preferably 100 μm or more, even more preferably 110 μm or more, and even more preferably 120 μm or more. On the other hand, the upper limit of the thickness is preferably 300 μm or less, more preferably 250 μm or less, even more preferably 220 μm or less, even more preferably 200 μm or less, and even more preferably 180 μm or less. By making the thickness of the bonding sheet 1 80 μm or more, not only can high heat dissipation properties be ensured, but also sufficient voltage resistance characteristics can be ensured. On the other hand, by making the thickness 300 μm or less, the bonded body I of the present invention can be made smaller or thinner, and the effect of reducing thermal resistance in the thickness direction due to the thin film can be obtained compared to an insulating thermally conductive layer made of a ceramic material. The thickness of the bonded sheet 1 is reduced by the heat pressing performed when producing the bonded body I of the present invention. From the viewpoint of insulation, the reduction in thickness is preferably 1% or more, more preferably 2% or more. On the other hand, from the viewpoint of maintaining the shape, the reduction in thickness is preferably 10% or less, more preferably 8% or less.

[0051] (Thermosetting Resin Composition Ib) The thermosetting resin composition Ib is not particularly limited as long as it contains a thermosetting resin and an inorganic filler and the bonding sheet 1 satisfies the above-described physical properties.

[0052] As the thermosetting resin, conventionally known resins can be used, such as epoxy resins, phenolic resins, urea resins, melamine resins, polyester (unsaturated polyester) resins, polyimide resins, silicone resins, polyurethane resins, maleimide resins, cyanate resins, and benzoxazine. Among these, it is preferable that the thermosetting resin contains an epoxy resin. The thermosetting resin can be a mixture of one or more of these resins.

[0053] As the inorganic filler, conventionally known inorganic fillers can be used, for example, particles of nitrides such as boron nitride, metal oxides such as alumina, etc. Note that the inorganic filler can be used alone or in combination of two or more of these inorganic fillers.

[0054] Among these, the inorganic filler preferably contains boron nitride agglomerated particles, i.e., boron nitride agglomerated particles formed by agglomeration of boron nitride primary particles, because they have little moisture absorption during heat molding, low toxicity, can efficiently increase thermal conductivity, and can impart high insulating properties to the bonding sheet 1. The agglomerated structure of the boron nitride agglomerated particles is preferably a house-of-card structure from the viewpoint of improving thermal conductivity. That is, the boron nitride agglomerated particles preferably have a house-of-card structure. A house-of-card structure is a structure in which plate-shaped particles are stacked in a complex manner without being oriented, as described in "Ceramics 43 No. 2" (published by the Ceramic Society of Japan, 2008). More specifically, it refers to a structure in which the planar surfaces of primary particles forming the agglomerated particles are in contact with the end faces of other primary particles present within the agglomerated particles. Due to their structural characteristics, boron nitride agglomerated particles with a house-of-card structure have extremely high fracture strength and can be prevented from collapsing when pressurized during the manufacturing process of the bonding sheet 1. Therefore, primary particles that are normally oriented in the longitudinal direction of the sheet can be made to exist in random directions. Therefore, by using boron nitride agglomerated particles having a house-of-card structure, the proportion of primary particles with the ab plane oriented in the thickness direction of the joining sheet 1 can be increased, thereby enabling effective heat conduction in the thickness direction of the joining sheet 1 and further increasing the thermal conductivity in the thickness direction.

[0055] The content of the thermosetting resin is preferably 5% by mass or more and 99% by mass or less, based on 100% by mass of the total solid content of the thermosetting resin composition Ib excluding the inorganic filler. A content of 5% by mass or more of the thermosetting resin is preferred because it improves moldability, while a content of 99% by mass or less allows the content of other components to be ensured and improves thermal conductivity. From this perspective, the content of the thermosetting resin is preferably 5% by mass or more and 99% by mass or less, based on 100% by mass of the total solid content of the thermosetting resin composition Ib excluding the inorganic filler. It is more preferred that the content be 10% by mass or more, more preferably 20% by mass or more, more preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more, while it is even more preferred that the content be 98% by mass or less.

[0056] The total inorganic filler content is preferably 40% by mass or more and 90% by mass or less, relative to 100% by mass of the total solids content of the thermosetting resin composition Ib. If the total inorganic filler content is 40% by mass or more, thermal conductivity can be improved, while if it is 90% by mass or less, adhesion and insulating properties can be improved. From this perspective, the total inorganic filler content is preferably 40% by mass or more, relative to 100% by mass of the total solids content of the thermosetting resin composition Ib, and is more preferably 50% by mass or more, more preferably 53% by mass or more, and even more preferably 55% by mass or more. On the other hand, it is preferably 90% by mass or less, and even more preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 72% by mass or less.

[0057] As described above, the thermosetting resin preferably contains an epoxy resin, and the inorganic filler preferably contains boron nitride agglomerated particles formed by agglomeration of primary particles of boron nitride, from the viewpoints of water resistance and low dielectric constant. Among these, from the viewpoints of high thermal conductivity and high withstand voltage, the boron nitride agglomerated particles preferably contain boron nitride agglomerated particles having a house-of-card structure, and preferably have a spherical shape. In this case, the content of the boron nitride agglomerated particles having a house-of-card structure is preferably 40% by mass or more and 90% by mass or less, more preferably 50% by mass or more or 80% by mass or less, and even more preferably 55% by mass or more or 70% by mass or less, relative to 100% by mass of the total solids content of the thermosetting resin composition Ib.

[0058] The thermosetting resin composition Ib may be a composition containing, in addition to the thermosetting resin and inorganic filler, other polymers, curing agents, curing accelerators, organic solvents, and other components as necessary. These may be conventionally known compositions, such as those described in International Publication No. 2023 / 189030.

[0059] <Method for manufacturing the joined body I of the present invention> Next, a method for manufacturing the joined body I of the present invention will be described. Examples of methods for manufacturing the joined body I of the present invention include a method in which the present thermosetting sheet Ia (joining sheet 1) is placed between the upper metal-containing member 2 and the lower metal-containing member 3, and pressing conditions such as pressing pressure, pressing temperature, and pressing configuration are controlled, or a method in which a joining sheet 1 having regions with different resin area ratios, void area ratios, or average void sizes is prepared in advance and placed between the upper metal-containing member 2 and the lower metal-containing member 3. The former method of controlling pressing conditions is preferred. However, the method described below is an example of a method for manufacturing the joined body I of the present invention, and is not limited to the following method.

[0060] As an example of a method for producing the joined body I of the present invention, a method for producing a joined body can be given, which involves: placing the present thermosetting sheet Ia (joining sheet 1) formed by molding the present thermosetting resin composition Ib into a sheet on the lower metal-containing member 3; applying uniform pressure to bond the lower metal-containing member 3 and the present thermosetting sheet Ia (joining sheet 1); then, placing the upper metal-containing member 2 on the present thermosetting sheet Ia (joining sheet 1); applying uniform pressure to bond the present thermosetting sheet Ia (joining sheet 1) and the upper metal-containing member 2. In this case, the present thermosetting sheet Ia (joining sheet 1) is preferably subjected to low-temperature aging in an environment of -50°C or higher and 0°C or lower before being placed on the lower metal-containing member 3 as described above. Note that the term "present thermosetting sheet Ia (joining sheet 1)" is used because the present thermosetting sheet Ia is also the joining sheet 1. This will be explained in more detail below.

[0061] First, it is preferable to place the thermosetting sheet Ia (joining sheet 1) on the lower metal-containing member 3 and apply uniform pressure (first pressurization) to bond the lower metal-containing member 3 and the thermosetting sheet Ia (joining sheet 1). In this case, any material such as copy paper, fluorine-based film such as Teflon, silicone rubber sheet, carbon paper, graphite sheet, or the like can be used as a cushioning material to ensure uniform pressure.

[0062] Next, it is preferable to place the upper metal-containing member 2 on the thermosetting sheet Ia (joining sheet 1) and apply uniform pressure (second pressurization) to bond the thermosetting sheet Ia (joining sheet 1) and the upper metal-containing member 2 together. That is, the thermosetting sheet Ia (joining sheet 1), which overlaps both the upper metal-containing member 2 and the lower metal-containing member 3 when viewed in cross section, is pressed, and the entire thermosetting sheet Ia (joining sheet 1) is heated to thermally harden it, bonding the upper metal-containing member 2 and the lower metal-containing member 3 to the front and back of the joined body sheet 1, thereby producing the joined body I of the present invention. At this time, the area of ​​the lower surface of the upper metal-containing member 2 is preferably 80% to 100% of the area of ​​the upper surface of the thermosetting sheet Ia (joining sheet 1). At this time, multiple upper metal-containing members 2 may be bonded in sheet form. In addition, any other material such as copy paper, fluorine-based film such as Teflon, silicone rubber sheet, carbon paper, graphite sheet, etc. can be used as a cushioning material to make the pressure uniform.

[0063] The first pressurization is sufficient if it is possible to temporarily fix the thermosetting sheet Ia (joining sheet 1) on the lower metal-containing member 3, so it is preferable to apply pressure so that a load of 0.5 MPa or more and 10 MPa or less is applied to the thermosetting sheet Ia (joining sheet 1), and it is even more preferable to apply pressure so that a load of 1 MPa or more or 9 MPa or less, and of these, a load of 2 MPa or more or 8 MPa or less is applied.

[0064] By applying the second pressurization, the thermosetting sheet Ia (joining sheet 1), which overlaps both the upper metal-containing member 2 and the lower metal-containing member 3 in cross section, is pressed, causing the sheet to flow laterally, increasing the resin ratio in the edge region 1A. Furthermore, the voids also flow laterally while being crushed, increasing the size of the voids in the edge region 1A and increasing the void ratio. Furthermore, by preventing the secondary particles of inorganic fillers, such as boron nitride agglomerated particles, from breaking, the contact between the inorganic fillers is improved, making it easier to form heat conduction paths and improving thermal conductivity. Furthermore, by reducing the viscosity of the resin component through high-temperature pressurization, the thermosetting sheet Ia (joining sheet 1) flows at the micro-edges, thereby alleviating stress in the edge region 1A, where pressure tends to concentrate locally during high-pressure pressing. From this perspective, it is desirable to apply a load of 2 MPa or more during the second pressurization. The load is preferably 4 MPa or more, more preferably 5 MPa or more, and even more preferably 6 MPa or more. The load is preferably 150 MPa or less, more preferably 100 MPa or less, and even more preferably 20 MPa or less.

[0065] Heating may be performed simultaneously during the second pressurization. The heating temperature (product temperature) at this time is preferably 10°C or higher, more preferably 20°C or higher, and even more preferably 30°C or higher. The heating temperature is preferably 300°C or lower, more preferably 250°C or lower, and even more preferably 200°C or lower. By performing the second pressurization within this temperature range, the melt viscosity of the resin in the thermosetting sheet Ia (bonding sheet 1) can be reduced, making the sheet more likely to flow laterally and increasing the resin ratio in the edge region 1A. In addition, the voids can be made to flow more easily laterally while being crushed, thereby increasing the size of the voids in the edge region 1A and increasing the void ratio.

[0066] As a specific example, the upper and lower top plates of the pressure press are preheated, and the upper metal-containing member 2 is stacked on the thermosetting sheet Ia (joining sheet 1) stacked on the lower metal-containing member 3 to form a laminate. This laminate is then set in the pressure press and pressed between the upper and lower top plates, allowing for simultaneous pressurization and heating. Alternatively, the thermosetting sheet Ia (joining sheet 1) is stacked on the lower metal-containing member 3, and the upper metal-containing member 2 is stacked on the thermosetting sheet Ia (joining sheet 1). The laminate is then set in the pressure press, and the pressure press or its press unit is heated to apply pressure, allowing for simultaneous pressurization and heating. In this case, both regions 1A and 1B of the thermosetting sheet Ia (joining sheet 1) are heated. The temperature of the top plate can be considered the product temperature of the thermosetting sheet Ia (joining sheet 1).

[0067] The pressurization time for the second pressurization is not particularly limited. It is preferably 30 seconds or more, more preferably 1 minute or more, even more preferably 3 minutes or more, and particularly preferably 5 minutes or more. The time for the pressurization step is preferably 1 hour or less, more preferably 30 minutes or less, and even more preferably 20 minutes or less. When the pressurization time is equal to or less than the upper limit, the manufacturing time can be reduced, and production costs tend to be reduced. When the pressurization time is equal to or more than the lower limit, the void content in the thermosetting sheet Ia (bonding sheet 1) can be reduced, and heat transfer performance and voltage resistance characteristics tend to be improved.

[0068] After the second pressurization, the thermosetting sheet Ia (bonding sheet 1) may be cured by heating. In this case, the heating temperature (product temperature) is preferably 30°C to 400°C, more preferably 50°C or higher, and even more preferably 90°C or higher. On the other hand, it is preferably 300°C or lower, and even more preferably 250°C or lower.

[0069] As the pressure application method, various known presses for molding thermosetting resins can be used. From the viewpoint of preventing resin deterioration during heat pressing, it is particularly preferable to use a vacuum press that can reduce the amount of oxygen inside the press during heating, or a press equipped with a nitrogen substitution device. As the heating method, a method of controlling the temperature of the upper and lower top plates of the press can be mentioned.

[0070] It is preferable to subject the thermosetting sheet Ia to low-temperature aging in advance, i.e., at least before placing the thermosetting sheet Ia on the lower metal-containing member 3. Low-temperature aging can be performed, for example, by placing the thermosetting sheet Ia in an environment preferably between -50°C and 0°C, more preferably between -30°C and -5°C, for a period of preferably 5 minutes to 365 days, more preferably 1 hour to 7 days. Pressure application during low-temperature aging is not required. However, a small pressure of 0.1 kPa or less may be applied. Examples of timing for low-temperature aging include after application, after heat drying, and after pressurization. Among these, after pressurization is preferred. However, this pressurization is different from the heat pressing used to prepare the joined body I of the present invention, and refers to the pressurization used when preparing the thermosetting sheet Ia prior to that.

[0071] By subjecting the thermosetting sheet Ia to such low-temperature aging, the moisture inside the sheet can be frozen and dispersed as tiny ice particles, and even after returning to room temperature, small chambers of moisture are created, preventing the formation of large voids and preventing deterioration of insulation properties, while suppressing the occurrence of cracks when the sheet is bent due to moisture retention. Furthermore, the high dispersion of tiny voids in the sheet increases the fluidity of the resin component when pressurized, increasing the proportion of resin at the edges. At the same time, voids inside the sheet are more likely to be pushed out to the edges, and voids accumulated at the edges can be expected to connect and increase in size, and further, the effect of stress relaxation at the interface edges of the present invention joint I can be expected.

[0072] <<Jointed body II of the present invention>> A joined body according to another embodiment of the present invention (also referred to as "jointed body II of the present invention") is a joined body having a configuration in which an upper metal-containing member 12 and a lower metal-containing member 13 are joined to the front and back of a joining sheet 11, as shown in FIG. 3 , wherein the upper metal-containing member 12 and the lower metal-containing member 13 each have a metal portion on the joining surface with the joining sheet 11, the joining sheet 11 contains a thermosetting resin and an inorganic filler, and has voids therein, and when viewed in a cross section (thickness direction) of the joined body, the joining sheet 11 has a region 11A overlapping with both the upper metal-containing member 12 and the lower metal-containing member 13, and a region 11B overlapping only with the lower metal-containing member 13, and the area ratio of the voids present in the region 11B of the joining sheet 11 (porosity X Ｂ ) is the area ratio of voids present in the region 11A (porosity X Ａ ) is larger than the

[0073] The present invention joined body II is also a joined body having a configuration in which an upper metal-containing member 12 and a lower metal-containing member 13 are joined to the front and back of a joining sheet 11, wherein the upper metal-containing member 12 and the lower metal-containing member 13 each have a metal portion on the joining surface with the joining sheet 11, the joining sheet 11 contains a thermosetting resin and an inorganic filler and has voids therein, and when viewed in a cross section (thickness direction) of the joined body, the joining sheet 11 has a region 11A overlapping with both the upper metal-containing member 12 and the lower metal-containing member 13 and a region 11B overlapping only with the lower metal-containing member 13, and the storage modulus Y at 200°C of the region 11B of the joining sheet 11 is Ｂ is the storage modulus Y of the region 11A at 200 ° C. Ａ The bonded body may be characterized in that the bonded body is smaller than

[0074] In the power semiconductor device and the like described above, as shown in FIG. 3, in a bonded structure in which an upper metal-containing member 12 and a lower metal-containing member 13 are bonded to the front and back of a bonding sheet 11 (corresponding to the insulating substrate), when stress is applied to the bonding sheet 11 due to a difference in expansion coefficient between the members caused by a temperature change, when viewed in a cross section (thickness direction), it has been found that the pressure is locally concentrated not in a region 11A of the bonding sheet 11 where the bonding sheet 11 overlaps both the upper metal-containing member 12 and the lower metal-containing member 13, but in a peripheral region 11B, causing cracks and deformation in the peripheral region 11B. Furthermore, when manufacturing the above-mentioned joined body, if the upper metal-containing member 12 and the lower metal-containing member 13 are pressed against the joining sheet 11 under high pressure, as shown in Fig. 3, when viewed in cross section (thickness direction), the pressure is concentrated locally in the peripheral region 11B of the joining sheet 11, rather than in the region 11A of the joining sheet 11 where the joining sheet 11 overlaps both the upper metal-containing member 12 and the lower metal-containing member 13, resulting in cracks and deformation in the peripheral region 11B. Therefore, the object of the joined body II of the present invention is to provide a new joined body and a method for manufacturing the joined body, which is configured such that the upper metal-containing member 12 and the lower metal-containing member 13 are joined to the front and back of the joining sheet 11, and which can eliminate cracks and deformation in the peripheral region 11B of the region 11A of the joining sheet 11 where the joining sheet 11 overlaps both the upper metal-containing member 12 and the lower metal-containing member 13.

[0075] The present invention joined body II is a joined body having a configuration in which an upper metal-containing member 12 and a lower metal-containing member 13 are joined to the front and back of a joining sheet 11, and when the joined body is viewed in a cross section (thickness direction), the area ratio of voids present in a region 11A of the joining sheet 11 where the joining sheet 11 overlaps both the upper metal-containing member 12 and the lower metal-containing member 13 (porosity X Ａ ), the area ratio of voids present in the peripheral region 11B (void ratio X Ｂ ) or increase the storage modulus Y at 200 ° C. of the region 11A. Ａ In comparison, the storage modulus Y of the peripheral region 11B at 200°C is ＢBy lowering the temperature, cracks and deformations in this region 11B can be prevented during and after the manufacturing process of the bonded body.

[0076] As shown in FIG. 3 , the present invention bonded body II is a bonded body having a configuration in which an upper metal-containing member 12 and a lower metal-containing member 13 are bonded to the front and back of a bonding sheet 11. That is, the bonded body has a configuration in which the upper metal-containing member 12 is bonded to one side of the bonding sheet 11 and the lower metal-containing member 13 is bonded to the other side of the bonding sheet 11. In this case, it is preferable that the bonding sheet 11 and the upper metal-containing member 12 are directly bonded, and that the bonding sheet 11 and the lower metal-containing member 13 are directly bonded. "Direct bonding" means that the bonding is performed without the interposition of any other member, and does not involve the use of an adhesive (including solder). However, if the bonding surfaces of the bonding sheet 11, the upper metal-containing member 12, and the lower metal-containing member 13 have been subjected to a thin-layer surface treatment such as plating treatment (e.g., nickel plating or tin plating), chemical conversion treatment, or physical treatment, as described below, this is considered to be "direct bonding."

[0077] As shown in FIG. 3 , when the present invention bonded body II is viewed in cross section (thickness direction), the bonding sheet 11 has a region 11A overlapping both the upper metal-containing member 12 and the lower metal-containing member 13, and a region 11B overlapping only the lower metal-containing member 13. Region 11A of the bonding sheet 11 can also be said to be a region sandwiched between both the upper metal-containing member 12 and the lower metal-containing member 13. On the other hand, region 11B is a peripheral region of region 11A, and its lower surface is bonded to the lower metal-containing member 13, while its upper surface is not bonded to the upper metal-containing member 12. Note that the bonding surfaces of the bonding sheet 11, the upper metal-containing member 12, and the lower metal-containing member 13 may each be flat, as shown in FIG. 3 . However, each bonding surface may have a concave or convex portion.

[0078] In the present invention, the "cross section" of "when the bonded body is viewed in the cross section (thickness direction)" refers to a cross section cut in the thickness direction along the length or width direction of the bonded sheet 11.

[0079] (Porosity) The joining sheet 11 contains a thermosetting resin and an inorganic filler 111 and has voids 112 therein. The area ratio of the voids 112 present in the region 11B of the joining sheet 11 (porosity X Ｂ ) is the area ratio of the voids 112 present in the region 11A (void ratio X Ａ ) is preferably larger than the area ratio of voids present in the area 11B. In the case where the bonding sheet 11 has a configuration in which the upper metal-containing member 12 and the lower metal-containing member 13 are bonded to each other on the front and back sides, as described above, cracks and deformations may occur in the area 11B surrounding the area 11A of the bonding sheet 11 sandwiched between the upper metal-containing member 12 and the lower metal-containing member 13. However, if the area ratio of voids present in the area 11B (porosity X Ｂ ) is the area ratio of voids present in the region 11A (porosity X Ａ ), it has been found that the occurrence of cracks and deformations in the region 11B during and after the manufacturing of the bonded body can be suppressed. From this viewpoint, it is possible to determine the area ratio of voids present in the region 11A of the bonding sheet 11 (porosity X Ａ ) to the area ratio of voids present in the region 11B (porosity X Ｂ ) ratio (X Ｂ / X Ａ ) is preferably greater than 2.0, and more preferably 5.0 or greater, more preferably 10 or greater, more preferably 20 or greater, more preferably 50 or greater, more preferably 100 or greater, and even more preferably 200 or greater. On the other hand, from the viewpoint of suppressing the intrusion of moisture from the atmosphere between the upper metal-containing member 12 and the lower metal-containing member 13, the ratio (X Ｂ / X Ａ ) is more preferably 400 or less, and more preferably 300 or less.

[0080] The area ratio of voids present in the region 11A of the bonding sheet 11 (void ratio X Ａ From the viewpoint of withstand voltage, the area ratio of voids present in the region 11B of the joining sheet 11 (porosity X Ｂ) is preferably 0.5% or more and 20% or less, more preferably 1% or more or 15% or less, even more preferably 2% or more or 10% or less, even more preferably 3% or more or 9% or less, even more preferably 5% or more or 8% or less, from the viewpoint of suppressing cracking and deformation when bonding members together and maintaining a certain level of withstand voltage.

[0081] To adjust the area ratio (porosity) of voids present in the regions 11A and 11B of the joining sheet 11 as described above, the upper metal-containing member 12 and the lower metal-containing member 13 are placed on the front and back of the thermosetting sheet IIa described below, the region 11A of the joining sheet 11 is pressed, and the thermosetting sheet IIa is heat-cured. In this method, the pressing conditions, the type of thermosetting resin, the type of inorganic filler, the presence or absence and conditions of low-temperature aging, etc. may be adjusted. However, the present invention is not limited to such a method. Ａ and X Ｂ The total void area per unit cross-sectional area of ​​the voids present in each region of the bonding sheet 11 can be calculated using image analysis software based on cross-sectional photographs of each region of the bonding sheet 11, and the average value of the five fields of view can be calculated.

[0082] (Average Void Area) The average void area of ​​the voids 112 present in the region 11A of the bonding sheet 11 is 10 μm ２ Preferably it is 5 μm or less, and more preferably it is 5 μm or less. ２ Below, among them, 2 μm ２ Among these, 1.5 μm ２ The lower limit of the average void area is not particularly limited, and is preferably 0 μm or less. ２ The average void area of ​​the voids 112 present in the region 11B of the bonding sheet 11 is set to 20 μm or more for stress relaxation. ２ It is preferable that the thickness is 50 μm or more, and particularly 50 μm ２ Above all, 100 μm ２ Above all, 200 μm ２ On the other hand, from the viewpoint of suppressing the intrusion of moisture in the atmosphere between the upper metal-containing member 12 and the lower metal-containing member 13, it is more preferable that the thickness is 700 μm or more. ２ Preferably it is 600 μm or less, and more preferably it is 600 μm or less.２ Below, among them, 500 μm ２ Below, among them, 300 μm ２ It is more preferable that the average void area of ​​the voids in regions 11A and 11B of bonding sheet 11 is adjusted as described above by the same method as the above-described method for adjusting the void ratio. The average void area of ​​the voids in regions 11A and 11B of bonding sheet 11 can be calculated as the average value of five fields of view using image analysis software based on cross-sectional photographs of each region of bonding sheet 11.

[0083] (Storage modulus) The bonding sheet 11 has a storage modulus Y Ｂ is the storage modulus Y at 200 ° C. of the region 11A Ａ In the case where the joining sheet 11 has a configuration in which the upper metal-containing member 12 and the lower metal-containing member 13 are joined to the front and back of the joining sheet 11, the storage modulus Y Ｂ is the storage modulus Y at 200 ° C. of the region 11A. Ａ From this viewpoint, it has been found that by making the storage modulus Y at 200° C. in the region 11A smaller than 11B, cracking and deformation in the region 11B can be suppressed during and after the manufacturing of the bonded body. Ａ Storage modulus Y at 200 ° C. in region 11B Ｂ The ratio (Y Ｂ / Y Ａ ) is preferably 0.8 or less, more preferably 0.79 or less, even more preferably 0.75 or less, and even more preferably 0.73 or less. On the other hand, from the viewpoint of resistance to external impacts, etc., the ratio (Y Ｂ / Y Ａ ) is more preferably 0.1 or more, more preferably 0.5 or more, and even more preferably 0.6 or more.

[0084] Storage modulus Y of region 11A of bonding sheet 11 at 200 ° C. Ａ is 1.0 × 10 from the viewpoint of mechanical strength and adhesive strength. ９ Pa or more 1.0×10 １１ Pa or less, and more preferably 2.0 × 10９ Pa or more or 8.0 x 10 １０ Pa or less, especially 3.0 × 10 ９ Pa or more or 2.0 x 10 １０ Pa or less, especially 5.0 × 10 ９ Pa or more or 1.0 x 10 １０ On the other hand, the storage modulus Y of the region 11B of the joining sheet 11 at 200° C. Ｂ is set to 1.0 × 10 from the viewpoint of suppressing cracks and deformations when bonding the members and mitigating the stress that occurs. ８ Pa or more 1.0×10 １１ Pa or less, and more preferably 5.0 × 10 ８ Pa or more or 5.0 x 10 １０ Pa or less, especially 1.0 x 10 ９ Pa or more or 1.0 x 10 １０ Pa or less, especially 3.0 × 10 ９ Pa or more or 1.0 x 10 １０ It is more preferable that the viscosity is 0.1 Pa or less.

[0085] To adjust the storage modulus at 200°C of the regions 11A and 11B of the joining sheet 11 as described above, the upper metal-containing member 12 and the lower metal-containing member 13 are placed on the front and back of the thermosetting sheet IIa described below, the region 11A of the joining sheet 11 is pressed, and the thermosetting sheet IIa is thermally cured by adjusting the pressure conditions, the type of thermosetting resin, the type of inorganic filler, whether or not low-temperature aging is performed and the conditions for it, etc. However, the present invention is not limited to such a method. The storage modulus at 200°C Y Ａ and Y Ｂ In this example, only the bonded sheet 11 can be separated from the bonded body, and the storage modulus of the regions 11A and 11B at 200°C can be measured. However, in Example II-1 described later, a bonded sheet was produced with the same composition and under the same pressure and heating conditions as in Example II-1, and the storage modulus of the regions 11A and 11B at 200°C was measured. The same applies to the porosity and thermal conductivity.

[0086] In addition, the bonding sheet 11 of the present invention has an area ratio of voids present in the region 11B of the bonding sheet 11 (void ratio X Ｂ) is the area ratio of voids present in the region 11A (porosity X Ａ ) or the storage modulus Y of the region 11B of the joining sheet 11 at 200 ° C. Ｂ is the storage modulus Y at 200 ° C. of region 11A Ａ It is sufficient that the area ratio of the voids present in the region 11B of the joining sheet 11 (porosity X Ｂ ) is the area ratio of voids present in the region 11A (porosity X Ａ ) and the storage modulus Y of the region 11B of the joining sheet 11 at 200 ° C. Ｂ is the storage modulus Y at 200 ° C. of region 11A Ａ It is smaller than

[0087] (Thermal Conductivity) When the bonded body II of the present invention is used for applications such as power semiconductor devices, industrial equipment, automotive equipment, and power generation energy, the thermal conductivity in the thickness direction of the region 11A of the bonding sheet 11 is preferably 10 W / m K or more, more preferably 11 W / m K or more, and even more preferably 12 W / m K or more. On the other hand, it is preferably 25 W / m K or less, and even more preferably 20 W / m K or less.

[0088] To adjust the thermal conductivity of the region 11A of the joining sheet 11 as described above, the upper metal-containing member 12 and the lower metal-containing member 13 are placed on the front and back of the thermosetting sheet IIa described below, the region 11A of the joining sheet 11 is pressurized, and the thermosetting sheet IIa is thermally cured. In this method, the pressing conditions, the type of thermosetting resin, the type of inorganic filler, and the presence and condition of low-temperature aging can be adjusted. However, this method is not limited to this. The thermal conductivity in the thickness direction of the region 11A of the joining sheet 11 can be measured by the following method. For example, the thermal resistance value can be measured using a thermal resistance measuring device, and the thermal conductivity can be calculated from the slope of a graph plotting the thermal resistance value against the thickness.

[0089] (Breakdown voltage (BDV)) When the present invention bonded body II is used for applications such as power semiconductor devices, industrial equipment, automotive equipment, and power generation energy, the breakdown voltage of the region 11A of the bonding sheet 11 is preferably 5 kV or more, more preferably 5.5 kV or more, and even more preferably 6 kV or more. The higher the breakdown voltage, the better, and there is no particular upper limit.

[0090] To adjust the breakdown voltage of the region 11A of the joining sheet 11 within the above range, the upper metal-containing member 12 and the lower metal-containing member 13 are placed on the front and back of the thermosetting sheet IIa (described later), the region 11A of the joining sheet 11 is pressurized, and the thermosetting sheet IIa is thermally cured. In this method, the pressing conditions, the type of thermosetting resin, the type of inorganic filler, and the presence or absence and conditions of low-temperature aging may be adjusted. However, this method is not limited to this. The breakdown voltage of the region 11A of the joining sheet 11 can be measured by applying a voltage in the thickness direction of the joined body.

[0091] <Upper metal-containing member 12, lower metal-containing member 13> The upper metal-containing member 12 and the lower metal-containing member 13 are both similar to the upper metal-containing member 2 and the lower metal-containing member 3 of the present invention joined body I. That is, the upper metal-containing member 2 of the present invention joined body I will be read as the upper metal-containing member 12 of the present invention joined body II, and the lower metal-containing member 3 of the present invention joined body I will be read as the lower metal-containing member 13 of the present invention joined body II. In this case, the metal part 25, resin 26, semiconductor chip 27, and wiring member 28 in the present invention joined body I will be read as the metal part 121, resin 122, semiconductor chip 123, and wiring member 124, respectively.

[0092] <Joining Sheet 11> The joining sheet 11 contains a thermosetting resin and an inorganic filler 111, and has voids 112 therein.

[0093] The joining sheet 11 is a cured product of a thermosetting resin composition (referred to as "the present thermosetting resin composition IIb") containing a thermosetting resin and an inorganic filler. That is, the joining sheet 11 is a cured product of a thermosetting sheet (referred to as "the present thermosetting sheet IIa") obtained by molding the present thermosetting resin composition IIb into a sheet shape.

[0094] (Thickness) The thickness of the joint sheet 11 is the same as the thickness of the joint sheet 1 of the joint body I of the present invention.

[0095] (Thermosetting resin composition IIb) The composition of the thermosetting resin composition for forming the bonding sheet 11 is the same as the composition of the thermosetting resin composition for forming the bonding sheet 1. That is, the thermosetting resin composition IIb is the same as the thermosetting resin composition Ib in the bonding sheet 1.

[0096] <Method for manufacturing the jointed body II of the present invention> Next, a method for manufacturing the jointed body II of the present invention will be described. Examples of methods for manufacturing the jointed body II of the present invention include a method in which the thermosetting sheet IIa (joining sheet 11) is placed between the upper metal-containing member 12 and the lower metal-containing member 13 and press conditions such as press pressure, press temperature, and press configuration are controlled, or a method in which a joining sheet 11 having regions with different porosities and storage moduli is prepared in advance and placed between the upper metal-containing member 12 and the lower metal-containing member 13. The former method of controlling press conditions is preferred. However, the method described below is an example of a method for manufacturing the jointed body II of the present invention and is not limited to the following method.

[0097] As an example of a method for producing the joined body II of the present invention, a method for producing a joined body can be given in which the present thermosetting sheet IIa (joining sheet 11) obtained by molding the present thermosetting resin composition IIb containing a thermosetting resin and an inorganic filler into a sheet is placed on the lower metal-containing member 13, and a uniform pressure is applied to bond the lower metal-containing member 13 and the present thermosetting sheet IIa (joining sheet 11). Then, the upper metal-containing member 12 is placed on the present thermosetting sheet IIa (joining sheet 11), and pressure is applied to the region 11A that overlaps both the upper metal-containing member 12 and the lower metal-containing member 13 when viewed in cross section, thereby bonding the present thermosetting sheet IIa (joining sheet 11) and the upper metal-containing member 12. In this case, the present thermosetting sheet IIa (joining sheet 11) is preferably subjected to low-temperature aging in an environment of -50 ° C or higher and 0 ° C or lower before being placed on the lower metal-containing member 13 as described above. The reason why it is referred to as "the thermosetting sheet IIa (the joining sheet 11)" is that the thermosetting sheet IIa is also the joining sheet 11. A more detailed description will be given below.

[0098] First, it is preferable to place the thermosetting sheet IIa (joining sheet 11) on the lower metal-containing member 13 and apply uniform pressure (first pressurization) to bond the lower metal-containing member 13 and the thermosetting sheet IIa (joining sheet 11). In this case, any cushioning material such as copy paper, a fluorine-based film such as Teflon, a silicone rubber sheet, carbon paper, or a graphite sheet can be used to ensure uniform pressure.

[0099] Next, it is preferable to place the upper metal-containing member 12 on the thermosetting sheet IIa (joining sheet 11) and apply uniform pressure (second pressurization) to bond the thermosetting sheet IIa (joining sheet 11) and the upper metal-containing member 12 together. That is, the region 11A of the thermosetting sheet IIa (joining sheet 11) that overlaps both the upper metal-containing member 12 and the lower metal-containing member 13 when viewed in cross section is pressurized, and the entire thermosetting sheet IIa (joining sheet 11) is heated to thermally harden it, bonding the upper metal-containing member 12 and the lower metal-containing member 13 to the front and back of the joined body sheet 1, thereby producing the joined body II of the present invention. In this case, multiple upper metal-containing members 12 may be bonded together in sheet form. In addition, any other material, such as copy paper, a fluorine-based film such as Teflon, a silicone rubber sheet, carbon paper, or a graphite sheet, can be used as a cushioning material to uniformly apply pressure.

[0100] The first pressurization is sufficient if it is possible to temporarily fix the thermosetting sheet IIa (joining sheet 11) on the lower metal-containing member 13, so it is preferable to apply pressure so that a load of 0.5 MPa or more and 10 MPa or less is applied to the thermosetting sheet IIa (joining sheet 11), and it is even more preferable to apply pressure so that a load of 1 MPa or more or 9 MPa or less, and of these, a load of 2 MPa or more or 8 MPa or less is applied.

[0101] By applying pressure to the region 11A of the thermosetting sheet IIa (joining sheet 11) that overlaps both the upper metal-containing member 12 and the lower metal-containing member 13 when viewed in cross section, the voids present in the region 11A are crushed, and the area ratio of the voids (void ratio X Ａ) can be reduced. Furthermore, the secondary particles of the inorganic filler, for example, boron nitride agglomerated particles, are not destroyed, and the porosity is reduced to increase thermal conductivity, while the contact between the inorganic fillers is improved, making it easier to form thermal conduction paths, thereby increasing thermal conductivity. From this perspective, it is desirable to apply a load of 2 MPa or more in the second pressurization. The load is preferably 4 MPa or more, more preferably 5 MPa or more, and even more preferably 6 MPa or more. The load is preferably 150 MPa or less, more preferably 100 MPa or less, and even more preferably 20 MPa or less.

[0102] Heating may be performed simultaneously with the second pressurization. The heating temperature (product temperature) is preferably 10°C or higher, more preferably 20°C or higher, and even more preferably 30°C or higher. The heating temperature is preferably 300°C or lower, more preferably 250°C or lower, and even more preferably 200°C or lower. By performing the second pressurization within this temperature range, the melt viscosity of the resin in the thermosetting sheet IIa (bonding sheet 11) can be reduced, and voids and gaps in the thermosetting sheet IIa (bonding sheet 11) can be further reduced. Furthermore, heating at or below the above upper limit tends to suppress decomposition of organic components in the thermosetting sheet IIa (bonding sheet 11) and voids caused by residual solvent.

[0103] As a specific example, the upper and lower top plates of the pressure press are preheated, and the upper metal-containing member 12 is stacked on the thermosetting sheet IIa (joining sheet 11) stacked on the lower metal-containing member 13 to form a laminate. This laminate is then set in the pressure press and pressed between the upper and lower top plates, allowing for simultaneous pressurization and heating. Alternatively, the thermosetting sheet IIa (joining sheet 11) is stacked on the lower metal-containing member 13, and the upper metal-containing member 12 is stacked on the thermosetting sheet IIa (joining sheet 11). This laminate is then set in the pressure press, and the pressure press or its press unit is heated to apply pressure, allowing for simultaneous pressurization and heating. In this case, both regions 11A and 11B of the thermosetting sheet IIa (joining sheet 11) are heated. The temperature of the top plate can be considered the product temperature of the thermosetting sheet IIa (joining sheet 11).

[0104] The pressurization time of the second pressurization is not particularly limited. It is preferably 30 seconds or more, more preferably 1 minute or more, even more preferably 3 minutes or more, and particularly preferably 5 minutes or more. The time of the pressurization step is preferably 1 hour or less, more preferably 30 minutes or less, and even more preferably 20 minutes or less. When the pressurization time is equal to or less than the above upper limit, the manufacturing time can be reduced, and production costs tend to be reduced. When the pressurization time is equal to or more than the above lower limit, voids and gaps in the thermosetting sheet IIa (bonding sheet 11) can be sufficiently removed, and heat transfer performance and voltage resistance characteristics tend to be improved.

[0105] After the second pressurization, the thermosetting sheet IIa (bonding sheet 11) may be cured by heating. In this case, the heating temperature (product temperature) is preferably 30°C to 400°C, more preferably 50°C or higher, and even more preferably 90°C or higher. On the other hand, it is preferably 300°C or lower, and even more preferably 250°C or lower.

[0106] As the pressure application method, various known presses for molding thermosetting resins can be used. From the viewpoint of preventing resin deterioration during heat pressing, it is particularly preferable to use a vacuum press that can reduce the amount of oxygen inside the press during heating, or a press equipped with a nitrogen substitution device. As the heating method, a method of controlling the temperature of the upper and lower top plates of the press can be mentioned.

[0107] It is preferable to subject the thermosetting sheet IIa to low-temperature aging in advance, i.e., at least before placing the thermosetting sheet IIa on the lower metal-containing member 13. Low-temperature aging can be performed, for example, by placing the thermosetting sheet IIa in an environment preferably between -50°C and 0°C, more preferably between -30°C and -5°C, for a period of preferably 5 minutes to 365 days, more preferably 1 hour to 7 days. Pressure application during low-temperature aging is not required. However, a small pressure of 0.1 kPa or less may be applied. Examples of timing for low-temperature aging include after application, after heat drying, and after pressurization. Among these, after pressurization is preferred. However, this pressurization is different from the heat pressing used to prepare the joined body II of the present invention, and refers to the pressurization used to prepare the thermosetting sheet IIa prior to that.

[0108] By subjecting this thermosetting sheet IIa to such low-temperature aging, the moisture inside the sheet can be frozen and dispersed as tiny ice particles, and even after returning to room temperature, small chambers of moisture are created that are confined in tiny spaces, preventing the formation of large voids and preventing deterioration of insulation properties while suppressing the occurrence of cracks when the sheet is bent due to moisture retention. Furthermore, by highly dispersing the tiny voids within the sheet, the fluidity of the resin component when pressurized is increased, making it easier for inorganic filler particles, such as boron nitride agglomerated particles, to stack with each other, achieving high thermal conductivity and, due to the stress relaxation effect, making the sheet less susceptible to cracking and deformation.

[0109] <<Jointed body III of the present invention>> A joined body according to yet another example of an embodiment of the present invention (also referred to as “jointed body III of the present invention”) is a joined body having a configuration in which two or more upper metal-containing members 22 are joined to a front surface of a joining sheet 21 and a lower metal-containing member 23 is joined to a rear surface of the joining sheet 21, wherein the upper metal-containing members 22 and the lower metal-containing members 23 each have a metal portion on a joining surface with the joining sheet 21, the joining sheet 21 contains a thermosetting resin and an inorganic filler and has voids therein, when the joined body is viewed in a cross section (thickness direction), the two or more upper metal-containing members 22 are joined to the joining sheet 21 with a blank portion 24 between adjacent upper metal-containing members 22, and the thickness of a region 21A of the joining sheet 21 where the joining sheet 21 is joined to the upper metal-containing member 22 is T Ａ The thickness of the region 21B of the joining sheet 21 that is not joined to the upper metal-containing member 22, i.e., the region 21B of the joining sheet 21 in the blank portion 24, is T Ｂ When this is the case, the thickness T of the region 21A is Ａ The thickness T of the region 21B Ｂ The ratio (T Ｂ / T Ａ ) is 1.02 or more.

[0110] In the above-mentioned power semiconductor device and the like, as shown in Figure 8, in a joined body having a configuration in which two or more upper metal-containing members (corresponding to the "electronic component such as a semiconductor element") 200 are joined on a joining sheet 100 (corresponding to the "insulating substrate") with a distance between adjacent upper metal-containing members 200, when current is applied to the upper metal-containing members 200, there is a concern that creeping discharge may occur because the creeping distance (thick line in Figure 8) between the conductor (metal portion) 201 included in one upper metal-containing member 200 and the conductor (metal portion) 201 included in the adjacent upper metal-containing member 200 is linear and short. Furthermore, in response to demands for designing higher-output modules, it becomes necessary to bond more upper metal-containing members 200 on the same sheet, which may further exacerbate the above-mentioned concern. Therefore, the object of the present invention, the joined body III, is to provide a new joined body having a configuration in which two or more upper metal-containing members 22 are joined to the surface of a joining sheet 21 and a lower metal-containing member 23 is joined to the back surface of the joining sheet 21, and which can make the current flow distance (creepage distance) between the conductor (metal portion) included in the upper metal-containing member 22 and the conductor (metal portion) included in the adjacent upper metal-containing member 22 longer than in the conventional example shown in Figure 8, and a method for manufacturing the joined body.

[0111] The present invention joined body III relates to a joined body having a configuration in which two or more upper metal-containing members 22 are joined to the front surface of a joining sheet 21 and a lower metal-containing member 23 is joined to the rear surface of the joining sheet 21, and the two or more upper metal-containing members 22 are joined to the joining sheet 21 with a blank space 24 between adjacent upper metal-containing members 22, and the interface between the upper metal-containing members 22 and the joining sheet 21 is positioned below the surface of the blank space 24 to provide a step, thereby reducing the thickness T of the region 21A of the joining sheet 21 where the joining sheet 21 is joined to the upper metal-containing members 22. Ａ The thickness T of the region 21B of the joining sheet 21 that is not joined to the upper metal-containing member 22, i.e., the region 21B of the joining sheet 21 in the blank portion 24, is Ｂ The thickness T of the region 21A is preferably larger than the thickness T of the region 21A. Ａ The thickness T of the region 21B Ｂ The ratio (T Ｂ / TＡ ) to 1.02 or more, (T Ｂ -T Ａ ) × 2, the electrical conduction distance (creepage distance) between the metal portion of the upper metal-containing member 22 and the metal portion of the adjacent upper metal-containing member 22 can be made longer than in the conventional example shown in FIG. 8 . As a result, it is expected that the risk of creepage discharge when current is applied to the upper metal-containing member 22 can be reduced. Furthermore, for example, when used in a humid environment, the reach distance of moisture in the air when it penetrates into the joint interface between the metal portion of the upper metal-containing member 22 and the joining sheet 21 can be increased, thereby reducing the risk of moisture absorption and mitigating the cause of failure. Furthermore, since the interface between the upper metal-containing member 22 and the joining sheet 21 is located below the creepage of the blank portion 24, it is possible to prevent discharge from the interface between the upper metal-containing member 22 and the joining sheet 21 via creepage discharge at the blank portion 24 to the interface between the adjacent upper metal-containing member 22 and the joining sheet 21. It is also expected that it will be more difficult for moisture in the air to penetrate into the interface between the sheet and the conductive metal portion contained in the upper metal-containing member 22.

[0112] As shown in FIG. 5 , the present invention joined body III is a joined body having a configuration in which two or more upper metal-containing members 22 are joined to the front surface of a joining sheet 21 and a lower metal-containing member 23 is joined to the rear surface of the joining sheet 21. That is, the joined body has a configuration in which the upper metal-containing member 22 is joined to one side of the joining sheet 21 and the lower metal-containing member 23 is joined to the other side of the joining sheet 21. In this case, it is preferable that the joining sheet 21 and the upper metal-containing member 22 are directly joined, and that the joining sheet 21 and the lower metal-containing member 23 are directly joined. "Direct joining" means that the joining is performed without the intermediation of other members, including without the use of adhesives (including solder). However, if the joining surfaces of the joining sheet 21, the upper metal-containing members 22, and the lower metal-containing members 23 have been subjected to a thin-layer surface treatment such as nickel plating or tin plating, a chemical conversion treatment, or a physical treatment, as described below, this is considered to be "direct joining."

[0113] As shown in Figure 5, when the joined body III of the present invention is viewed in cross section (thickness direction), two or more upper metal-containing members 22 are joined to the joining sheet 21 with a blank space 24 between adjacent upper metal-containing members 22, and the joining sheet 21 has a region 21A joined to the upper metal-containing member 22, in other words, a region 21A sandwiched between both the upper metal-containing member 22 and the lower metal-containing member 23, and a region 21B not joined to the upper metal-containing member 22, in other words, a region 21B in the blank space 24.

[0114] In the present invention, the "cross section" of "when the bonded body is viewed in the cross section (thickness direction)" refers to a cross section cut in the thickness direction along the length or width direction of the bonded sheet 21.

[0115] The joining surfaces of the joining sheet 21, the upper metal-containing member 22, and the lower metal-containing member 23 may be flat as shown in Fig. 5. However, each joining surface may have a recess or a protrusion.

[0116] (Blank portion) In the present invention joined body III, when two or more upper metal-containing members 22 are joined to the surface of the joining sheet 21, as shown in FIG. 6 , the two or more upper metal-containing members 22 are joined to the joining sheet 21 with a blank portion 24 between adjacent upper metal-containing members 22, and further, the interface 22 a between the upper metal-containing member 22 and the joining sheet 21 is positioned below the creeping surface 24 a of the blank portion 24 to provide a step, thereby reducing the thickness T Ａ The thickness T of the region 21B of the joining sheet 21 that is not joined to the upper metal-containing member 22, i.e., the region 21B of the joining sheet 21 in the blank portion 24, is Ｂ is larger than the thickness T Ａ The thickness T of the region 21B Ｂ The ratio (T Ｂ / T Ａ ) is set to 1.02 or more, and as shown in FIG. Ｂ -T Ａ) × 2, the current flow distance, in other words, the creepage distance (thick line portion in FIG. 6 ) between the metal portion of the upper metal-containing member 22 and the metal portion of the adjacent upper metal-containing member 22 can be made longer than in the conventional example shown in FIG. 8 . This is expected to reduce the risk of creepage discharge when current is applied to the upper metal-containing member 22. Furthermore, for example, when used in a humid environment, the reach distance of moisture in the air when it penetrates into the bonding interface between the metal portion of the upper metal-containing member 22 and the bonding sheet 21 can be increased, which can reduce the risk of moisture absorption and is expected to alleviate the cause of failure. Furthermore, since the interface 22a between the upper metal-containing member 22 and the joining sheet 21 is located below the creeping surface 24a of the blank portion 24, it is possible to prevent discharge from the interface 22a between the upper metal-containing member 22 and the joining sheet 21 via the creeping surface 24a of the blank portion 24 to the interface 22a between the adjacent upper metal-containing member 22 and the joining sheet 21, and it is also expected to make it even more difficult for moisture in the air to enter the interface between the conductive metal portion contained in the upper metal-containing member 22 and the sheet.

[0117] The width of the space 24 provided between an upper metal-containing member 22 and an adjacent upper metal-containing member 22, i.e., the lateral distance to the adjacent upper metal-containing member 22, is preferably 1 mm or more, more preferably 2 mm or more, and even more preferably 3 mm or more, from the viewpoint of ensuring a creepage distance. On the other hand, from the viewpoint of increasing the input power to one module by bonding many members on the same sheet, it is preferably 100 mm or less, more preferably 50 mm or less, and even more preferably 30 mm or less.

[0118] The ratio of the width of the blank portion 24 to the width of the upper metal-containing member 22, i.e., the lateral distance to the adjacent upper metal-containing member 22 (blank portion 24 / upper metal-containing member 22), is preferably 0.05 or more, more preferably 0.07 or more, and even more preferably 0.1 or more, from the viewpoint of ensuring creepage distance. On the other hand, from the viewpoint of increasing the input power to one module by bonding many members on the same sheet, it is preferably 10 or less, more preferably 5 or less, and even more preferably 3 or less.

[0119] (Thickness of the Joining Sheet 21) In the joined body III of the present invention, when viewed in cross section (thickness direction) of the joined body, the thickness T Ａ The thickness T of the region 21B of the joining sheet 21 that is not joined to the upper metal-containing member 22, i.e., the region 21B of the joining sheet 21 in the blank portion 24, is Ｂ is larger than the thickness T Ａ The thickness T of the region 21B Ｂ The ratio (T Ｂ / T Ａ The thickness T of the region 21A is 1.02 or more. Ａ The thickness T of the region 21B is Ｂ is larger than the thickness T Ａ The thickness T of the region 21B Ｂ The ratio (T Ｂ / T Ａ ) is 1.02 or more, it is possible to ensure a conduction distance (creepage distance) between a conductive metal portion included in the upper metal-containing member 22 and a conductive metal portion included in an adjacent upper metal-containing member 22, thereby reducing the risk of creepage discharge and making it more difficult for moisture in the air to penetrate into the interface between the conductive metal portion included in the upper metal-containing member 22 and the sheet. Furthermore, since the interface 22a between the upper metal-containing member 22 and the bonding sheet 21 is located below the creepage surface 24a of the blank portion 24, it is possible to prevent discharge from the interface 22a between the upper metal-containing member 22 and the bonding sheet 21 to the interface 22a between the adjacent upper metal-containing member 22 and the bonding sheet 21 via creepage discharge of the blank portion 24, and it is also expected to make it more difficult for moisture in the air to penetrate into the interface between the conductive metal portion included in the upper metal-containing member 22 and the sheet.

[0120] From this viewpoint, the thickness T Ａ The thickness T of the region 21B Ｂ The ratio (T Ｂ / T Ａ) is preferably 1.02 or more, more preferably 1.03 or more, even more preferably 1.05 or more, and even more preferably 1.10 or more, and even more preferably 1.14 or more. Ｂ / T Ａ If ) is too large, the distance from the conductive metal portion contained in the upper metal-containing member 22 to the lower metal-containing member 23 becomes short, and there is a concern about the risk of insulation breakdown in the sheet thickness direction. Therefore, it is preferably 1.4 or less, more preferably 1.3 or less, and even more preferably 1.2 or less.

[0121] From the same viewpoint, the thickness T Ａ and the thickness T of the region 21B Ｂ The difference between (T Ｂ -T Ａ ) is preferably 3 μm or more, more preferably 4 μm or more, even more preferably 5 μm or more, and even more preferably 10 μm or more, even more preferably 15 μm or more, and even more preferably 19 μm or more. However, the difference (T Ｂ -T Ａ If the thickness tf is too large, the distance from the conductive metal portion contained in the upper metal-containing member 22 to the lower metal-containing member 23 becomes short, and there is a risk of insulation breakdown in the sheet thickness direction. Therefore, the thickness tf is preferably 30 μm or less, more preferably 25 μm or less, and even more preferably 20 μm or less.

[0122] Thickness T of the region 21A of the bonding sheet 21 Ａ and the thickness T of the region 21B Ｂ In order to adjust the relationship between the thickness T and the thickness T of the thermosetting sheet IIIa as described above, the upper metal-containing member 22 is placed on the surface of the thermosetting sheet IIIa, which will be described later, and the region 21A of the joining sheet 21 is pressed into the thermosetting sheet IIIa, and then the thermosetting sheet IIIa is heated and cured. Also, the type of thermosetting resin, the type of inorganic filler, whether low-temperature aging is performed and the conditions for it, etc. may be adjusted. However, the present invention is not limited to such a method. In addition, the thickness T of the region 21A may be adjusted by adjusting the type of thermosetting resin, the type of inorganic filler, whether low-temperature aging is performed and the conditions for it, etc. Ａ and the thickness T of the region 21B ＢThe measurement method is not particularly limited, and the thickness may be measured by separating only the bonded sheet 21 from the bonded body and measuring with a thickness meter such as a micrometer, or may be measured from a cross-sectional photograph using a scanning electron microscope (SEM) or the like.

[0123] Thickness T of the bonding sheet 21 in the region 21A Ａ When the present invention bonded body III is used for, for example, a power semiconductor, an industrial device, an in-vehicle device, a power generating energy device, etc., the thickness T Ａ is preferably 80 μm or more, more preferably 100 μm or more, even more preferably 110 μm or more, and even more preferably 120 μm or more. Ａ The upper limit of the thickness T in the region 21A of the bonding sheet 21 is preferably 300 μm or less, more preferably 250 μm or less, even more preferably 220 μm or less, still more preferably 200 μm or less, and still more preferably 180 μm or less. Ａ By setting the thickness to 80 μm or more, not only can high heat dissipation be ensured but also sufficient voltage resistance can be ensured. On the other hand, by setting the thickness to 300 μm or less, the present invention joined body III can be made smaller and thinner, and the thinner thickness can provide the effect of reducing thermal resistance in the thickness direction compared to an insulating thermally conductive layer made of a ceramic material.

[0124] (Thermal Conductivity) When the present invention bonded body III is used for applications such as power semiconductor devices, industrial equipment, in-vehicle equipment, and power generation energy, the thermal conductivity in the thickness direction of the region 21A of the bonding sheet 21 is preferably 10 W / m K or more, more preferably 11 W / m K or more, and even more preferably 12 W / m K or more. On the other hand, it is preferably 25 W / m K or less, and even more preferably 20 W / m K or less.

[0125] To adjust the thermal conductivity of the region 21A of the bonding sheet 21 as described above, the upper metal-containing member 22 and the lower metal-containing member 23 are stacked on the front and back of the thermosetting sheet IIIa described below, the region 21A of the bonding sheet 21 is pressurized, and the thermosetting sheet IIIa is thermally cured. In this method, the pressurization conditions, the type of thermosetting resin, the type of inorganic filler, and the presence and condition of low-temperature aging can be adjusted. However, this method is not limited to this. The thermal conductivity in the thickness direction of the region 21A of the bonding sheet 21 can be measured by the following method. For example, the thermal conductivity can be determined from the slope of a graph plotting thermal resistance values ​​against thickness using a thermal resistance measuring device. In this case, the bonding sheet 21 alone can be separated from the bonded body, and the thermal conductivity in the thickness direction of the region 21A can be measured. However, in Example III-1 described below, a bonding sheet was prepared with the same composition and the same pressurization and heating conditions as Example III-1, and the thermal conductivity in the thickness direction of the region 21A was measured.

[0126] (Breakdown voltage (BDV)) When the present invention bonded body III is used for applications such as power semiconductor devices, industrial equipment, automotive equipment, and power generation energy, the breakdown voltage of the region 21A of the bonding sheet 21 is preferably 5 kV or more, more preferably 5.5 kV or more, and even more preferably 6 kV or more. The higher the breakdown voltage, the better, and there is no particular upper limit.

[0127] To adjust the breakdown voltage of the region 21A of the joining sheet 21 within the above range, the upper metal-containing member 22 and the lower metal-containing member 23 are placed on the front and back of the thermosetting sheet IIIa (described later), the region 21A of the joining sheet 21 is pressurized, and the thermosetting sheet IIIa is thermally cured. In this method, the pressurization conditions, the type of thermosetting resin, the type of inorganic filler, and the presence or absence and conditions of low-temperature aging may be adjusted. However, this method is not limited to this. The breakdown voltage of the region 21A of the joining sheet 21 can be measured by applying a voltage in the thickness direction of the joined body.

[0128] <Upper metal-containing member 22, lower metal-containing member 23> The upper metal-containing member 22 and the lower metal-containing member 23 are both similar to the upper metal-containing member 2 and the lower metal-containing member 3 of the present invention joined body I. That is, the upper metal-containing member 2 of the present invention joined body I will be read as the upper metal-containing member 22 of the present invention joined body III, and the lower metal-containing member 3 of the present invention joined body I will be read as the lower metal-containing member 23 of the present invention joined body III. In this case, the metal part 25, resin 26, semiconductor chip 27, and wiring member 28 in the present invention joined body I will be read as the metal part 221, resin 222, semiconductor chip 223, and wiring member 224, respectively.

[0129] <Bonding Sheet 21> The bonding sheet 21 contains a thermosetting resin and an inorganic filler 211, and has voids 212 therein.

[0130] The joining sheet 21 is a cured product of a thermosetting resin composition (referred to as "the present thermosetting resin composition IIIb") containing a thermosetting resin and an inorganic filler. That is, the joining sheet 21 is a cured product of a thermosetting sheet (referred to as "the present thermosetting sheet IIIa") obtained by molding the present thermosetting resin composition IIIb into a sheet shape.

[0131] (Thermosetting resin composition IIIb) The composition of the thermosetting resin composition for forming the bonding sheet 21 is the same as the composition of the thermosetting resin composition for forming the bonding sheet 1. That is, the thermosetting resin composition IIIb is the same as the thermosetting resin composition Ib in the bonding sheet 1.

[0132] <Method for Manufacturing Joint III of the Present Invention> Next, a method for manufacturing the joint III of the present invention will be described. Examples of methods for manufacturing the joint III of the present invention include a method in which the thermosetting sheet IIIa (joining sheet 21) is placed between the upper metal-containing member 22 and the lower metal-containing member 23 and press conditions such as press pressure, press temperature, and press configuration are controlled, or a method in which a joining sheet 21 having regions with different degrees of deformation due to pressure is prepared in advance and placed between the metal-containing member 2 and the lower metal-containing member 23. The former method of controlling press conditions is preferred. However, the method described below is an example of a method for manufacturing the joint III of the present invention and is not limited to the following method.

[0133] As an example of a method for producing the joined body III of the present invention, the present thermosetting sheet IIIa (joining sheet 21) obtained by forming the present thermosetting resin composition IIIb containing a thermosetting resin and an inorganic filler into a sheet shape is placed on the lower metal-containing member 23, and a uniform pressure is applied to bond the lower metal-containing member 23 and the present thermosetting sheet IIIa (joining sheet 21). After that, two or more upper metal-containing members 22 are placed on the present thermosetting sheet IIIa (joining sheet 21), and the upper metal-containing members 22 are bonded to each other so that .... A method for producing a bonded body can be exemplified by applying pressure to the region 21A overlapping both the metal-containing member 22 and the lower metal-containing member 23, forcing the upper metal-containing member 22 into the thermosetting sheet IIIa (joining sheet 21), and positioning the interface 22a between the upper metal-containing member 22 and the thermosetting sheet IIIa (joining sheet 21) below the creeping surface 24a of the blank portion 24, thereby bonding the thermosetting sheet IIIa (joining sheet 21) and the upper metal-containing member 22 together. In this case, the thermosetting sheet IIIa (joining sheet 21) is preferably subjected to low-temperature aging in advance, i.e., in an environment of −50°C or higher and 0°C or lower, before being placed on the lower metal-containing member 23 as described above. The term “thermosetting sheet IIIa (joining sheet 21)” is used because the thermosetting sheet IIIa is also the joining sheet 21. This will be described in more detail below.

[0134] First, it is preferable to place the thermosetting sheet IIIa (joining sheet 21) on the lower metal-containing member 23 and apply uniform pressure (first pressurization) to bond the lower metal-containing member 23 and the thermosetting sheet IIIa (joining sheet 21). In this case, any cushioning material such as copy paper, a fluorine-based film such as Teflon, a silicone rubber sheet, carbon paper, or a graphite sheet can be used to ensure uniform pressure.

[0135] Next, it is preferable to stack two or more upper metal-containing members 22 on the thermosetting sheet IIIa (joining sheet 21) with a predetermined distance between adjacent upper metal-containing members 22, and then apply further uniform pressure (second pressurization) to bond the thermosetting sheet IIIa (joining sheet 21) and the upper metal-containing members 22 together. That is, pressure is applied to the region 21A of the thermosetting sheet IIIa (joining sheet 21) that overlaps both the upper metal-containing member 22 and the lower metal-containing member 23 when viewed in cross section, and the upper metal-containing member 22 is pressed into the thermosetting sheet IIIa (joining sheet 21). In other words, the upper metal-containing member 22 is pressed so that the top surface of the thermosetting sheet IIIa (joining sheet 21) is recessed, and the interface 22a between the upper metal-containing member 22 and the thermosetting sheet IIIa (joining sheet 21) is positioned below the creeping surface 24a of the blank portion 24. Furthermore, the entire thermosetting sheet IIIa (joining sheet 21) is heated to thermally harden it, and the upper metal-containing member 22 and the lower metal-containing member 23 are joined to the front and back of the thermosetting sheet IIIa (joining sheet 21), thereby producing the joined body III of the present invention. In this case, by arranging two or more upper metal-containing members 22 at a predetermined distance between adjacent upper metal-containing members 22 and overlapping them, the two or more upper metal-containing members 22 can be joined to the thermosetting sheet IIIa (joining sheet 21) with a blank portion 24 between the adjacent upper metal-containing members 22. Furthermore, by applying pressure to push the upper metal-containing members 22 into the thermosetting sheet IIIa (joining sheet 21) and positioning the interface 22a between the upper metal-containing members 22 and the thermosetting sheet IIIa (joining sheet 21) below the creeping surface 24a of the blank portion 24, the thickness T of the region 21A of the joining sheet 21 can be reduced. Ａ The thickness T of the region 21B of the joining sheet 21 that is not joined to the upper metal-containing member 22, i.e., the region 21B of the joining sheet 21 in the blank portion 24, is Ｂ The thickness T of the region 21A is preferably larger than the thickness T of the region 21A. Ａ The thickness T of the region 21B Ｂ The ratio (T Ｂ / T Ａ ) can be made 1.02 or more.

[0136] The distance between adjacent upper metal-containing members 22, in other words, the width of the blank portion 24, is preferably 2 mm or more, more preferably 3 mm or more, and even more preferably 4 mm or more, from the viewpoint of ensuring the creepage distance as described above. On the other hand, from the viewpoint of increasing the input power to one module by bonding many members onto the same sheet, it is preferably 100 mm or less, more preferably 50 mm or less, and even more preferably 30 mm or less.

[0137] The two or more upper metal-containing members 22 may be the same or different from one another. To make the pressure uniform, any material such as copy paper, a fluorine-based film such as Teflon, a silicone rubber sheet, carbon paper, or a graphite sheet can be used as a cushioning material.

[0138] The first pressurization is sufficient if it can temporarily fix the thermosetting sheet IIIa (joining sheet 21) on the lower metal-containing member 23, so it is preferable to apply pressure so that a load of 0.5 MPa or more and 10 MPa or less is applied to the thermosetting sheet IIIa (joining sheet 21), and it is even more preferable to apply pressure so that a load of 1 MPa or more or 9 MPa or less, and of these, a load of 2 MPa or more or 8 MPa or less is applied.

[0139] By the second pressurization, the region 21A of the thermosetting sheet IIIa (joining sheet 21) that overlaps both the upper metal-containing member 22 and the lower metal-containing member 23 when viewed in cross section is pressed, and the upper metal-containing member 22 is pressed into the thermosetting sheet IIIa (joining sheet 21). The interface 22a between the upper metal-containing member 22 and the thermosetting sheet IIIa (joining sheet 21) is positioned below the creeping surface 24a of the blank portion 24, and the thickness T in the region 21B of the joining sheet 21 is reduced. Ｂ The thickness T of the region 21A is ＡFrom this viewpoint, it is desirable to apply a load of 2 MPa or more in the second pressurization. The load is preferably 4 MPa or more, more preferably 5 MPa or more, and even more preferably 6 MPa or more. The load is also preferably 150 MPa or less, more preferably 100 MPa or less, and even more preferably 20 MPa or less.

[0140] Heating may be performed simultaneously with the second pressurization. The heating temperature (product temperature) at this time is preferably 10°C or higher, more preferably 20°C or higher, and even more preferably 30°C or higher. The heating temperature is preferably 300°C or lower, more preferably 250°C or lower, and even more preferably 200°C or lower. By performing the second pressurization within this temperature range, the melt viscosity of the resin in the thermosetting sheet IIIa (bonding sheet 21) can be reduced, and voids and gaps in the thermosetting sheet IIIa (bonding sheet 21) can be further reduced. Furthermore, heating at or below the above upper limit tends to suppress decomposition of organic components in the thermosetting sheet IIIa (bonding sheet 21) and voids caused by residual solvent.

[0141] As a specific example, the upper and lower top plates of the pressure press are preheated, and the upper metal-containing member 22 is stacked on the thermosetting sheet IIIa (joining sheet 21) stacked on the lower metal-containing member 23 to form a laminate. This laminate is then set in the pressure press and pressed between the upper and lower top plates, allowing for simultaneous pressing and heating. Alternatively, the thermosetting sheet IIIa (joining sheet 21) is stacked on the lower metal-containing member 23, and the upper metal-containing member 22 is stacked on the thermosetting sheet IIIa (joining sheet 21). The laminate is then set in the pressure press, and the pressure press or its press unit is heated to apply pressure, allowing for simultaneous pressing and heating. In this case, both regions 21A and 21B of the thermosetting sheet IIIa (joining sheet 21) are heated. The temperature of the top plate can be considered the product temperature of the thermosetting sheet IIIa (joining sheet 21).

[0142] The pressurization time of the second pressurization is not particularly limited. It is preferably 30 seconds or more, more preferably 1 minute or more, even more preferably 3 minutes or more, and particularly preferably 5 minutes or more. The time of the pressurization step is preferably 1 hour or less, more preferably 30 minutes or less, and even more preferably 20 minutes or less. When the pressurization time is equal to or less than the upper limit, the manufacturing time can be reduced, and production costs tend to be reduced. When the pressurization time is equal to or more than the lower limit, voids and gaps in the thermosetting sheet IIIa (bonding sheet 21) can be sufficiently removed, and heat transfer performance and voltage resistance characteristics tend to be improved.

[0143] After the second pressurization, the thermosetting sheet IIIa (bonding sheet 21) may be cured by heating. In this case, the heating temperature (product temperature) is preferably 30°C to 400°C, more preferably 50°C or higher, and even more preferably 90°C or higher. On the other hand, it is preferably 300°C or lower, and even more preferably 250°C or lower.

[0144] As the pressure application method, various known presses for molding thermosetting resins can be used. From the viewpoint of preventing resin deterioration during heat pressing, it is particularly preferable to use a vacuum press that can reduce the amount of oxygen inside the press during heating, or a press equipped with a nitrogen substitution device. As the heating method, a method of controlling the temperature of the upper and lower top plates of the press can be mentioned.

[0145] It is preferable to subject the thermosetting sheet IIIa to low-temperature aging in advance, i.e., at least before placing the thermosetting sheet IIIa on the lower metal-containing member 23. Low-temperature aging can be performed, for example, by placing the thermosetting sheet IIIa in an environment preferably between -50°C and 0°C, more preferably between -30°C and -5°C, for a period of preferably 5 minutes to 365 days, more preferably 1 hour to 7 days. Pressure application during low-temperature aging is not required. However, a small pressure of 0.1 kPa or less may be applied. Examples of timing for low-temperature aging include after application, after heat drying, and after pressurization. Among these, after pressurization is preferred. However, this pressurization is different from the heat pressing used to prepare the present joined body III, and refers to the pressurization used to prepare the thermosetting sheet IIIa prior to that.

[0146] By subjecting the thermosetting sheet IIIa to such low-temperature aging, the moisture inside the sheet can be frozen and dispersed as tiny ice particles, and even after returning to room temperature, small chambers of moisture are created that are confined in tiny spaces, preventing the formation of large voids and preventing deterioration of insulation properties, while suppressing the occurrence of cracks when the sheet is bent due to moisture retention. Furthermore, by performing low-temperature aging, the micro-voids can be highly dispersed within the sheet, thereby increasing the fluidity of the resin component when pressurized. As a result, inorganic fillers, such as agglomerated particles of boron nitride, tend to stack with each other, which tends to create a difference in thickness between region 21A and region 21B, and the thickness T of region 21A tends to decrease. Ａ The thickness T of the region 21B Ｂ The ratio (T Ｂ / T Ａ ) can be made 1.02 or more, the current-carrying distance (creepage distance) can be increased, and it is thought that a decrease in the breakdown voltage (BDV) can be suppressed.

[0147] <Explanation of Terms, etc.> In the present invention, when the term "film" is used, it includes "sheet," and when the term "sheet" is used, it includes "film." In the present invention, when it is written "α to β" (α and β are any numbers), it means "α or more and β or less," unless otherwise specified, and it also means "preferably greater than α" or "preferably smaller than β." Furthermore, when it is written "α or more" or "α≦" (α is any number), it means "preferably greater than α" unless otherwise specified, and when it is written "β or less" or "≦β" (β is any number), it also means "preferably smaller than β" unless otherwise specified.

[0148] An example of an embodiment of the present invention will be described below, but the present invention is not limited to the embodiment described below.

[0149] <Examples and Comparative Examples of Joint I of the Present Invention> Example I-1 and Comparative Examples I-1 and I-2 of Joint I of the Present Invention will be described.

[0150] (Upper metal-containing member 2) As the upper metal-containing member 2, a member measuring 21 mm in length, 16 mm in width, and 5 mm in thickness was prepared, which had a configuration in which the periphery, except for the bottom surface, of a copper plate measuring 16 mm in length, 13 mm in width, and 2 mm in thickness as the metal portion 25 was covered with epoxy resin as the resin 26.

[0151] (Lower Metal-Containing Member 3) As the lower metal-containing member 3, a copper plate having a length of 40 mm, a width of 80 mm, and a thickness of 2 mm was prepared.

[0152] (Preparation of Thermosetting Sheet 1a) A high molecular weight epoxy resin (mass average molecular weight in terms of polystyrene: 30,000, epoxy equivalent: 9,000 g / equivalent, density: approximately 1.2 g / cm ３ 9 parts by mass of a polyfunctional epoxy resin (molecular weight 500 or less, density approximately 1.2 g / cm) containing a structure having four or more glycidyl groups in one molecule ３ ) 7 parts by mass, biphenyl-type solid epoxy resin (molecular weight: about 400, density: about 1.2 g / cm ３) 15 parts by mass of spherical boron nitride agglomerated particles having a card house structure (average particle size (D50) 45 μm, maximum particle size (Dmax) 90 μm) 63 parts by mass of spherical boron nitride agglomerated particles having a card house structure (average particle size (D50) 45 μm, maximum particle size (Dmax) 90 μm), 5 parts by mass of a phenolic resin-based curing agent, 0.4 parts by mass of a curing catalyst (2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(17')]-ethyl-s-triazine, molecular weight: 247, properties: solid, melting point: 215-225 ° C), and 0.4 parts by mass of a curing catalyst (2-phenyl-4,5-dihydroxymethylimidazole, molecular weight: 204, properties: solid, melting point: dec. 230, so that the melting point is 230 ° C or higher), to which methyl ethyl ketone and cyclohexanone were added so that the solid content concentration was 74 mass%, and mixed using a planetary stirring device to prepare a slurry-like thermosetting resin composition.

[0153] The maximum particle size (Dmax) and average particle size (D50) of the boron nitride agglomerated particles are determined by dispersing the boron nitride agglomerated particles in a pure water medium containing sodium hexametaphosphate as a dispersion stabilizer, measuring the volumetric particle size distribution using a laser diffraction / scattering particle size distribution analyzer LA-300 (manufactured by Horiba, Ltd.), and determining the maximum particle size Dmax and the particle size at 50% of cumulative volume (average particle size D50) from the obtained particle size distribution.

[0154] The thus obtained thermosetting resin composition in a slurry form was applied to a PET substrate by a doctor blade method, and the applied composition was dried by heating at 60°C (ambient temperature) for 120 minutes. Then, the applied composition was pressurized at 42°C (product temperature) and 1500 kgf / cm using a press. ２ The thermosetting sheet 1a was placed in a freezer at -20°C for 2 days without applying any weight, and subjected to low-temperature aging to obtain a thermosetting sheet 1a.

[0155] Example I-1 Using the above-described upper metal-containing member 2, lower metal-containing member 3, and thermosetting sheet 1a, a bonded body was produced as follows.

[0156] The thermosetting sheet 1a was placed on top of the lower metal-containing member 3 so that the entire lower surface of the thermosetting sheet 1a overlapped the lower metal-containing member 3 to form a laminate, and copy paper was placed on the top and bottom of this laminate.This was then set in a pressure press whose top and bottom top plates had been preheated to 80°C, and hot-pressed at 80°C (product temperature) with a load of 2 MPa applied for 5 minutes. Next, the upper metal-containing member 2 was placed on top of the thermosetting sheet 1a which had been placed on the lower metal-containing member 3, so that the entire top surface of the thermosetting sheet 1a overlapped the upper metal-containing member 2 and that the entire bottom metal portion of the upper metal-containing member 2 overlapped the sheet 1a to form a laminate. Copy paper was then placed on the top and bottom of this laminate, and this was set in a pressure press whose top and bottom top plates had been preheated to 180°C, and hot-pressed at 180°C (product temperature) with a load of 6 MPa applied for 30 minutes, resulting in a bonded structure in which the upper metal-containing member 2 and the lower metal-containing member 3 were bonded to the front and back of the 150 μm-thick bonding sheet 1, as shown in Figure 1.

[0157] When the joining sheet 1 is viewed in cross section, the resin area ratio P in the end region 1A extending from the left or right end of the joining sheet 1 to the inside 300 μm is １Ａ is 51%, and the resin area ratio P １Ｂ is 45%, and the ratio of the two (P １Ａ / P １Ｂ The void area ratio S in the edge region 1A was 1.13. １Ａ is 5.5%, and the void area ratio S １Ｂ is 0.8%, and the ratio of the two (S １Ａ / S １Ｂ The average void size L in the edge region 1A was 6.8. １Ａ is 14 μm ２ / number, and the average void size L １Ｂ is 1.6 μm ２ / number, and the ratio of the two (L １Ａ / L １Ｂ) was 8.75. The area of ​​the metal portion exposed on the underside of the upper metal-containing member 2 was 68% of the area of ​​the bonding sheet 1, which was 68% of the central region 1B of the bonding sheet 1, and the entire surface of the metal portion was in contact with the central region 1B of the bonding sheet 1. The dielectric breakdown voltage (BDV) of the bonding sheet 1 was confirmed to be 5 kV or more. The thermal conductivity of the bonding sheet 1 in the thickness direction was 14 W / m·K. An ultrasonic imaging device was used to observe the presence or absence of cracks or deformation in the bonding sheet 1 during manufacturing, and the interface between the metals (upper metal-containing member 2 and lower metal-containing member 3) and the bonding sheet 1. No cracks or deformation were observed, and no peeling was observed at the interface. The dielectric breakdown voltage (BDV) of the bonding sheet 1 after the thermal cycle test was confirmed to be 5 kV or more. After the thermal cycle test, an ultrasonic imaging device was used to observe whether or not there were any cracks or deformations in the bonding sheet 1 due to temperature changes after production, and the interface between the metal (upper metal-containing member 2 and lower metal-containing member 3) and the bonding sheet 1.No cracks or deformations were found, and no peeling was observed at the interface.

[0158] Comparative Example 1-1 A thermosetting sheet was obtained by aging the sheet in an environment at 100°C for 1 hour instead of the low-temperature aging in which the sheet was placed in a freezer at -20°C for 2 days in the preparation of the thermosetting sheet 1a. A bonded body was then prepared in the same manner as in Example I-1, except that the thermosetting sheet was used.

[0159] When the joining sheet 1 in this joined body is viewed in cross section, the resin area ratio P １Ａ The resin area ratio P １Ｂ is 44%, and the ratio of the two (P １Ａ / P １Ｂ The void area ratio S in the edge region 1A was 0.95. １Ａ is 7.0%, and the void area ratio S １Ｂ is 7.9%, and the ratio of the two (S １Ａ / S １Ｂ The average void size L in the edge region 1A was 0.89. １Ａ is 109 μm ２ / number, and the average void size L １Ｂ is 55 μm ２ / number, and the ratio of the two (L １Ａ / L １Ｂ ) was 1.98. The area of ​​the metal portion exposed on the underside of the upper metal-containing member 2 was 68% of the area of ​​the bonding sheet, which was 68% of the central region 1B of the bonding sheet 1, and the entire surface of the metal portion was in contact with the central region 1B of the bonding sheet. It was confirmed that the breakdown voltage (BDV) of the bonding sheet 1 after the thermal cycle test was less than 5 kV. After the thermal cycle test, an ultrasonic imaging device was used to observe the presence or absence of cracks or deformation in the bonding sheet 1 due to temperature changes after production, and the interface between the metals (upper metal-containing member 2 and lower metal-containing member 3) and the bonding sheet 1. Cracks and deformation were found, and peeling was also found at the interface.

[0160] Comparative Example I-2 A thermosetting sheet was obtained by aging the sheet in a 60°C environment for 3 days instead of the low-temperature aging in which the sheet was placed in a freezer at -20°C for 2 days in the preparation of the thermosetting sheet 1a. A bonded body was then prepared in the same manner as in Example I-1, except that the thermosetting sheet was used.

[0161] When the joining sheet 1 in this joined body is viewed in cross section, the resin area ratio P １Ａ is 40%, and the resin area ratio P １Ｂ is 37%, and the ratio of the two (P １Ａ / P １Ｂ The void area ratio S in the edge region 1A was 1.08. １Ａ is 6.6%, and the void area ratio S １Ｂ is 12%, and the ratio of the two (S １Ａ / S １Ｂ ) was 0.55. The average void size L in the edge region 1A １Ａ is 108 μm ２ / number, and the average void size L １Ｂ is 85 μm ２ / number, and the ratio of the two (L １Ａ / L１Ｂ ) was 1.27. The area of ​​the metal portion exposed on the underside of the upper metal-containing member 2 was 68% of the area of ​​the bonding sheet 1, which was 68% of the area of ​​the central region 1B of the bonding sheet 1, and the entire surface of the metal portion was in contact with the central region 1B of the bonding sheet 1. It was confirmed that the breakdown voltage (BDV) of the bonding sheet 1 after the thermal cycle test was less than 5 kV. After the thermal cycle test, an ultrasonic imaging device was used to observe the presence or absence of cracks or deformation in the bonding sheet 1 due to temperature changes after production, and the interface between the metals (upper metal-containing member 2 and lower metal-containing member 3) and the bonding sheet 1. Cracks and deformation were found, and peeling was also found at the interface.

[0162] <Methods for Measuring and Evaluating Physical Properties> The physical properties and evaluations of the bonded bodies produced in Example I-1 and Comparative Examples I-1 and I-2 were carried out as follows.

[0163] (Photographing a cross-sectional SEM image) A bonded sheet was produced under the same conditions as the bonded sheet 1 in the bonded bodies produced in Example I-1 and Comparative Examples I-1 to I-2. That is, a portion of the thermosetting sheet 1a was heat-pressed so that a load of 2 MPa was applied for 5 minutes at 80 ° C. (product temperature), and then heat-pressed so that a load of 6 MPa was applied for 30 minutes at 180 ° C. (product temperature) to produce a bonded sheet (measurement sample) having a region that was pressurized twice and a region that was not pressurized twice. An appropriate portion of this bonded sheet (measurement sample) was cut in the thickness direction along the width direction (lateral direction) using a shearing process (DSW3500P (manufactured by Meiwafosis Co., Ltd.)), and the cross section was used. Cross-sectional processing was performed by subjecting any portion of the cut surface of each sheet to ion milling (cross-section polisher SM-09010 (manufactured by JEOL)). Thereafter, an SEM scanning electron microscope (SU5000 (manufactured by Hitachi)) was used to observe the sample at an acceleration voltage of 10 kV and a magnification of 300 times to obtain an SEM image.

[0164] (Method of calculating resin area ratio) To calculate the resin area ratio, a 300 μm × 165 μm area was cut out at an arbitrary location in the SEM image obtained above, and the image of that area was analyzed using image analysis software. That is, the cut-out image was binarized, and the areas of the copper plate, inorganic filler, resin (i.e., the portion consisting of high molecular weight epoxy resin, multifunctional epoxy resin, biphenyl-type solid epoxy resin, phenolic resin-based curing agent, and curing catalyst), and voids were separated based on the difference in contrast. The area of ​​the resin region was divided by the total area of ​​the inorganic filler, resin, and voids, and the result was multiplied by 100 to obtain the filler area ratio (%). The resin area ratios (%) of the edge region 1A and the center 1B were shown as the average value of two fields of view.

[0165] (Method of calculating void area ratio) To calculate the void area ratio, a 300 μm × 165 μm area was cut out at an arbitrary location in the SEM image obtained above, and the image of that area was analyzed using image analysis software. That is, the cut-out image was binarized, and the areas of the copper plate, inorganic filler, resin (i.e., the portion consisting of high-molecular-weight epoxy resin, multifunctional epoxy resin, biphenyl-type solid epoxy resin, phenolic resin-based curing agent, and curing catalyst), and voids were separated based on the difference in contrast. The area of ​​the void region was divided by the total area of ​​the inorganic filler, resin, and voids, and the result was multiplied by 100 to obtain the filler area ratio (%). The void area ratios (%) of the edge region 1A and the center 1B were shown as the average value of two fields of view.

[0166] (Method of calculating the average void size) In the SEM image obtained in the same manner as above, a range of 300 μm×165 μm was cut out at an arbitrary point, and the area (μm ２ The average void size (μm) in the edge region 1A and the center 1B was calculated by dividing the average void size (μm) by the number of voids in the same region. ２ / number) is the average value of two fields of view (μm ２ / number of pieces).

[0167] (Measurement of Breakdown Voltage (BDV)) The bonded bodies obtained in Example I-1 and Comparative Examples I-1 and I-2 were immersed in Fluorinert FC-40 (manufactured by 3M), a voltage application jig was installed so that a voltage was applied between the metal part 25 of the upper metal-containing member 2 and the lower metal-containing member 3, and a voltage of 0.5 kV was applied to the region 1A of the bonding sheet 1 using an ultra-high voltage withstand voltage tester 7470 (manufactured by Keisoku Gijutsu Kenkyusho Co., Ltd.), and the voltage was increased by 0.5 kV every 60 seconds, and the breakdown voltage (BDV) was measured to confirm whether the breakdown voltage (BDV) was 5 kV or more.

[0168] (Measurement of thermal conductivity) A bonded sheet was prepared under the same conditions as the bonded sheet 1 in the bonded body prepared in Example I-1. That is, the thermosetting sheet 1a was heat-pressed at 80 ° C (product temperature) under a load of 2 MPa for 5 minutes, and then heat-pressed at 180 ° C (product temperature) under a load of 6 MPa for 30 minutes to prepare a bonded sheet (measurement sample) that was pressed twice. The thermal conductivity of the bonded sheet (measurement sample) was measured using a "T3ster DynTIM Tester" manufactured by Mentor Graphics. Two, three, or four bonded sheets (measurement samples) were stacked, and the thickness, area, and thermal resistance values ​​of four types of sheets with different thicknesses were measured. The thermal conductivity (25 ° C) in the sheet thickness direction in a steady-state method was determined from the slope represented by the thermal resistance value relative to the sheet thickness (in accordance with ASTM D5470). The probe size during measurement was 12.8 mm, the fixing pressure was 3400 kPa, and the measurement time was 300 seconds. To improve the adhesion between the sample and the probe, "OIL COMPOUND (product name: G-747)" manufactured by Shin-Etsu Chemical Co., Ltd. was used.

[0169] (Observation of cracks, deformation, and interface) The bonded structures produced in Example I-1 and Comparative Examples I-1 and I-2 were observed using an ultrasonic imaging device FinSAT (FS300III) (manufactured by Hitachi Power Solutions) to check for the presence or absence of cracks or deformation in the bonding sheet 1, and the interface between the metals (upper metal-containing member 2 and lower metal-containing member 3) and the bonding sheet 1. Measurements were performed using a probe with a frequency of 50 MHz, a gain of 30 dB, and a pitch of 0.2 mm, with the bonded structure (sample) placed in water. These results represent the presence or absence of cracks or deformation during manufacturing and the observation results for the interface.

[0170] (Thermal Cycle Test) The bonded bodies prepared in Example I-1 and Comparative Examples I-1 to I-2 were subjected to a thermal cycle test using a thermal shock tester TSA-41L-A (manufactured by Espec). The test conditions were as follows: starting from room temperature, cooling to -40 ° C, holding for 30 minutes, then returning to room temperature, then heating to 150 ° C (product temperature), holding for 30 minutes, and then returning to room temperature. This cycle was repeated 100 times. After the thermal cycle test, the dielectric breakdown voltage (BDV) was measured as described above, and it was confirmed whether the dielectric breakdown voltage (BDV) was 5 kV or more. Also, after the thermal cycle test, the presence or absence of cracks or deformation in the bonding sheet 1 and the interface between the metal (upper metal-containing member 2 and lower metal-containing member 3) and the bonding sheet 1 were observed using an ultrasonic imaging device as described above. These results are used to determine the presence or absence of cracks or deformation during temperature changes after production, and the observation results of the interface.

[0171] (Discussion) From the results of the above Example I-1 and Comparative Examples I-1 to I-2, as well as the results of the tests conducted by the present inventors, in a joined body having a configuration in which an upper metal-containing member 2 and a lower metal-containing member 3 are joined to the front and back of a joining sheet 1, the resin area ratio in the end region 1A extending from one of the left and right side ends of the joining sheet 1 to the inside by 300 μm is set to P １Ａ , the resin area ratio in the central region 1B other than the end region 1A is P １Ｂ When P １Ａ / P １Ｂ The value of is made larger than 1.10, or when the joining sheet 1 is viewed in cross section, the void area ratio in the edge region 1A from the left or right edge of the joining sheet 1 to the inside 300 μm is made smaller than S １Ａ, the void area ratio in the central region 1B other than the end region 1A is S １Ｂ When this is done, S １Ａ / S １Ｂ The value of is made larger than 1, or when the joining sheet 1 is viewed in cross section, the average void size in the end region 1A extending from the left or right end of the joining sheet 1 to the inside 300 μm is made larger than L １Ａ , the average void size in the central region 1B other than the end region 1A is L １Ｂ When this is done, L １Ａ / L １Ｂ It was found that by making the value of [mass ratio] greater than 2, cracking and deformation in the bonding sheet 1 can be suppressed even if stress is applied to the bonding sheet 1 due to differences in expansion coefficients between components caused by temperature changes.

[0172] P １Ａ / P １Ｂ By increasing the value of S to more than 1.10, that is, by increasing the resin ratio in the edge region 1A of the bonding sheet 1, it is possible to increase the stress relaxation effect, and it is presumed that even if stress is applied to the bonding sheet 1 due to differences in expansion coefficients between components caused by temperature changes in tests or mounting processes in which stress is particularly generated at the edge of the bonding sheet 1, cracks and deformations in the bonding sheet 1 can be suppressed. １Ａ / S １Ｂ By making the value of L larger than 1, the voids act as a buffer material in tests and mounting processes where stress is particularly generated at the edges of the bonding sheet 1, and by increasing the stress relaxation effect, it is presumed that even if stress is applied to the bonding sheet 1 due to differences in the expansion coefficients between components caused by temperature changes, cracks and deformations in the bonding sheet 1 can be suppressed. １Ａ / L １ＢIt is presumed that by making the value of [Delta] greater than 2, cracking and deformation in the bonding sheet 1 can be suppressed even if stress is applied to the bonding sheet 1 due to a difference in expansion coefficient between components caused by a temperature change in a test or mounting process in which stress is particularly generated at the edge of the bonding sheet 1. From the above-mentioned mechanism of action, it is considered that if at least one of the three requirements is satisfied, the object of the present invention of suppressing cracking and deformation in the bonding sheet 1 can be achieved even if stress is applied to the bonding sheet 1 due to a difference in expansion coefficient between components caused by a temperature change.

[0173] <Examples and Comparative Examples of the Inventive Joint II> Example II-1 and Comparative Example II-1 of the inventive joint II will be described.

[0174] (Upper metal-containing member 12) As the upper metal-containing member 12, a member measuring 21 mm in length, 16 mm in width, and 5 mm in thickness was prepared, which had a configuration in which the periphery, excluding the bottom surface, of a copper plate measuring 16 mm in length, 13 mm in width, and 2 mm in thickness as the metal portion 121 was covered with epoxy resin as the resin 122.

[0175] (Lower Metal-Containing Member 13) As the lower metal-containing member 13, a copper plate having a length of 40 mm, a width of 80 mm, and a thickness of 2 mm was prepared.

[0176] (Joining sheet 11) High molecular weight epoxy resin (mass average molecular weight in polystyrene equivalent: 30,000, epoxy equivalent: 9,000 g / equivalent, density: approximately 1.2 g / cm ３ 9 parts by mass of a polyfunctional epoxy resin (molecular weight 500 or less, density approximately 1.2 g / cm) containing a structure having four or more glycidyl groups in one molecule ３ ) 7 parts by mass, biphenyl-type solid epoxy resin (molecular weight: about 400, density: about 1.2 g / cm ３) 15 parts by mass of spherical boron nitride agglomerated particles having a card house structure (average particle size (D50) 45 μm, maximum particle size (Dmax) 90 μm) 63 parts by mass of spherical boron nitride agglomerated particles having a card house structure (average particle size (D50) 45 μm, maximum particle size (Dmax) 90 μm), 5 parts by mass of a phenolic resin-based curing agent, 0.4 parts by mass of a curing catalyst (2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(17')]-ethyl-s-triazine, molecular weight: 247, properties: solid, melting point: 215-225 ° C), and 0.4 parts by mass of a curing catalyst (2-phenyl-4,5-dihydroxymethylimidazole, molecular weight: 204, properties: solid, melting point: dec. 230, so that the melting point is 230 ° C or higher), to which methyl ethyl ketone and cyclohexanone were added so that the solid content concentration was 74 mass%, and mixed using a planetary stirring device to prepare a slurry-like thermosetting resin composition.

[0177] The average particle diameter (D50) and maximum particle diameter (Dmax) of the boron nitride agglomerated particles are determined by dispersing the boron nitride agglomerated particles in a pure water medium containing sodium hexametaphosphate as a dispersion stabilizer, measuring the volumetric particle size distribution using a laser diffraction / scattering particle size distribution analyzer LA-300 (manufactured by Horiba, Ltd.), and determining the maximum particle diameter Dmax and the particle diameter at 50% cumulative volume (average particle diameter D50) from the obtained particle size distribution.

[0178] The thus obtained thermosetting resin composition in a slurry form was applied to a PET substrate by a doctor blade method, and the applied composition was dried by heating at 60°C (ambient temperature) for 120 minutes. Then, the applied composition was pressurized at 42°C (product temperature) and 1500 kgf / cm using a press. ２ The thermosetting sheet 11a was then placed in a freezer at -20°C for 2 days without applying any weight, allowing it to undergo low-temperature aging, thereby obtaining a thermosetting sheet 11a.

[0179] Example II-1 Using the above-described upper metal-containing member 12, lower metal-containing member 13, and thermosetting sheet 11a, a bonded body was produced as follows.

[0180] A thermosetting sheet 11a was placed on the lower metal-containing member 13 to form a laminate, and copy paper was placed on the top and bottom of this laminate. The upper and lower top plates were preheated to 80 ° C. and placed in a press machine. The upper and lower top plates were then heated to 80 ° C. (product temperature) and a load of 2 MPa was applied for 5 minutes. Next, the upper metal-containing member 12 was placed on the thermosetting sheet 11a placed on the lower metal-containing member 13 to form a laminate. Copy paper was then placed on the top and bottom of this laminate. The upper and lower top plates were preheated to 180 ° C. and placed in a press machine. The upper and lower top plates were then heat-pressed at 180 ° C. (product temperature) for 30 minutes. As shown in Figures 3 and 4, the upper metal-containing member 12 and the lower metal-containing member 13 were bonded to the front and back of the 150 μm thick bonding sheet 11. A bonded body having regions 11A and 11B was obtained.

[0181] When the cross sections of the region 11A and the region 11B of the bonding sheet 11 were observed using a scanning electron microscope (SEM), it was confirmed that both the region 11A and the region 11B had voids. The area ratio of the voids present in the region 11A of the bonding sheet 11 (porosity X Ａ ) is 0.032%, and the area ratio of voids present in the region 11B (porosity X Ｂ ) was 7.2%. Ｂ / X Ａ The storage modulus at 200°C in the region 11A was 5.54 × 10 ９ Pa, and the storage modulus at 200°C in region 11B is 3.98 × 10 ９ It was Pa. Y Ｂ / Y Ａ was less than 0.8. 　 It was also confirmed that the BDV of the region 11A of the bonding sheet 11 was 5 kV or more. The thermal conductivity in the thickness direction of the region 11A of the bonding sheet 11 was 14 W / m·K. During and after the manufacturing process of the bonded body, the peripheral region 11B of the bonding sheet 11 around the region 11A was observed visually and with an ultrasonic imaging device for cracks and deformation, and no cracks or deformation were found.

[0182] Comparative Example II-1 A thermosetting sheet was obtained by aging the sheet in a 60°C environment for 3 days instead of the low-temperature aging in which the sheet was placed in a freezer at -20°C for 2 days in the preparation of the thermosetting sheet 11a. A bonded body was then prepared in the same manner as in Example II-1, except that the thermosetting sheet was used.

[0183] When the cross sections of the region 11A and the region 11B of the bonding sheet 11 were observed with a scanning electron microscope (SEM), it was confirmed that both the region 11A and the region 11B had voids. The storage modulus of the region 11A at 200° C. was 3.02×10 ９ Pa, and the storage modulus at 200°C in region 11B is 3.91 × 10 ９ It was Pa. 　 During and after the manufacturing of the bonded body, the surrounding area 11B of the area 11A of the bonding sheet 11 was observed visually and with an ultrasonic imaging device to check for cracks and deformations. Cracks and deformations were found.

[0184] <Methods for Measuring and Evaluating Physical Properties> The physical properties and evaluations of the bonded bodies produced in Example II-1 and Comparative Example II-1 were carried out as follows.

[0185] (Photographing a cross-sectional SEM image) A bonded sheet was produced under the same conditions as the bonded sheet 11 in the bonded body produced in Example II-1. That is, a portion of the thermosetting sheet 11a was heat-pressed so that a load of 2 MPa was applied for 5 minutes at 80 ° C. (product temperature), and then heat-pressed so that a load of 6 MPa was applied for 30 minutes at 180 ° C. (product temperature), to produce a bonded sheet (measurement sample) having a region 11A that was pressurized twice and a region 11B that was not pressurized twice. An appropriate portion of this bonded sheet (measurement sample) was cut in the thickness direction along the width direction (lateral direction) using a shearing process (DSW3500P (manufactured by Meiwafosis Co., Ltd.)), and the cross section was used. Cross-sectional processing was performed by subjecting any portion of the cut surface of each sheet to ion milling (cross-section polisher SM-09010 (manufactured by JEOL)). Thereafter, an SEM scanning electron microscope (SU5000 (manufactured by Hitachi)) was used to observe the sample at an acceleration voltage of 10 kV and a magnification of 500 times to obtain an SEM image.

[0186] (Method of calculating porosity) To calculate the porosity, a 254 μm × 75 μm area was cut out at an arbitrary location in the SEM image obtained above, and image analysis was performed on the image of that area using image analysis software. That is, the cut-out image was binarized, and the contrast area of ​​the inorganic filler and resin (i.e., the part consisting of high molecular weight epoxy resin, multifunctional epoxy resin, biphenyl-type solid epoxy resin, phenolic resin-based curing agent, and curing catalyst) that are the sheet constituents was extracted as voids. The area was divided by the area of ​​the cut-out area of ​​254 μm × 75 μm and multiplied by 100 to obtain the area ratio of voids, i.e., the void ratio (%). The area ratio of voids present in areas 11A and 11B, i.e., the porosity X Ａ (%), porosity X Ｂ The percentages are shown as the average values ​​of five fields. The results for Example II-1 are shown in Table 1.

[0187]

[0188] (Method of calculating average void area) In the SEM image obtained in the same manner as above, a range of 254 μm × 75 μm was cut out at an arbitrary location, and the image of that range was subjected to image analysis using image analysis software. That is, the cut-out image was binarized, and contrast regions greater than or equal to the inorganic filler and resin (i.e., the portion consisting of high molecular weight epoxy resin, multifunctional epoxy resin, biphenyl-type solid epoxy resin, phenolic resin-based curing agent, and curing catalyst) that are the sheet constituent components were extracted as voids, and the total void area of ​​the arbitrary location calculated using image analysis software was divided by the number of voids to determine the average void area of ​​each void. The average void area (μm ２ The results for Example II-1 are shown in Table 2.

[0189]

[0190] (Method for measuring storage modulus) A bonded sheet was prepared under the same conditions as the bonded sheet 11 in the bonded body prepared in Example II-1 and Comparative Example II-1. That is, a portion of the thermosetting sheet 11a was heat-pressed at 80 ° C (product temperature) under a load of 2 MPa for 5 minutes, and then heat-pressed at 180 ° C (product temperature) under a load of 6 MPa for 30 minutes to prepare a bonded sheet (measurement sample) having a region 11A that was pressurized twice and a region 11B that was not pressurized twice. Regions 11A and 11B of the bonded sheet (measurement sample) were each cut to a width of 3 mm to 10 mm, a length of 50 mm to 60 mm, and a thickness of 0.3 mm to 0.6 mm. The measurement was performed under the conditions of a chuck distance of 35 mm, a temperature rise of -150 ° C to 260 ° C at 2 ° C / min, and a measurement frequency of 1 Hz, and the storage modulus at 200 ° C was measured for regions 11A and 11B. The apparatus used was EXSTAR6000 DMS6100.

[0191] (Observation of voids) Appropriate locations of each of the regions 11A and 11B of the bonded bodies produced in Example II-1 and Comparative Example II-1 were cut in the thickness direction along the width direction (lateral direction) using a shearing process (DSW3500P (manufactured by Meiwafosis Co., Ltd.)). Cross-section processing was performed by subjecting arbitrary locations on the cut surfaces of each sheet to an ion milling process (Cross-section Polisher SM-09010 (manufactured by JEOL Ltd.)). The cross sections were observed using an SEM scanning electron microscope (SU5000 (manufactured by Hitachi Corporation)) at an acceleration voltage of 10 kV and a magnification of 300 times.

[0192] (Measurement of Breakdown Voltage (BDV)) The bonded body prepared in Example II-1 was immersed in Fluorinert FC-40 (manufactured by 3M), and a voltage application jig was installed so that a voltage was applied between the metal part 121 of the upper metal-containing member 12 and the lower metal-containing member 13. Using an ultra-high voltage withstand voltage tester 7470 (manufactured by Keisoku Gijutsu Kenkyusho Co., Ltd.), a voltage of 0.5 kV was applied to the region 11A of the bonding sheet 11, and the voltage was increased by 0.5 kV every 60 seconds, and the breakdown voltage (BDV) was measured to confirm whether the breakdown voltage (BDV) was 5 kV or more.

[0193] (Measurement of thermal conductivity) A bonded sheet was produced under the same conditions as the bonded sheet 11 in the bonded body produced in Example II-1. That is, a portion of the thermosetting sheet 11a was heat-pressed at 80 ° C. (product temperature) under a load of 2 MPa for 5 minutes, and then heat-pressed at 180 ° C. (product temperature) under a load of 6 MPa for 30 minutes to produce a bonded sheet (measurement sample) having a region 11A that was pressurized twice. The thermal conductivity of the region 11A of the bonded sheet (measurement sample) was measured using a "T3ster DynTIM Tester" manufactured by Mentor Graphics. Two, three, or four bonded sheets (measurement samples) were stacked, and the thickness, area, and thermal resistance value of region 11A of four types of sheets with different thicknesses were measured. The thermal conductivity (25°C) in the sheet thickness direction using the steady-state method was calculated from the slope represented by the thermal resistance value versus sheet thickness (in accordance with ASTM D5470). The probe size during measurement was φ12.8 mm, the fixing pressure was 3400 kPa, and the measurement time was 300 seconds. Shin-Etsu Chemical Co., Ltd.'s "OIL COMPOUND (product name: G-747)" was used to improve adhesion between the sample and the probe.

[0194] (Observation of cracks and deformation) The bonded structures produced in Example II-1 and Comparative Example II-1 were visually observed from above or from an oblique angle above, and the presence or absence of cracks and deformation in the peripheral region 11B of the region 11A of the bonding sheet 11 was visually observed during and after the manufacturing of the bonded structures. Furthermore, the bonded structures produced in Example II-1 and Comparative Example II-1 were observed during and after the manufacturing of the bonded structures for the presence or absence of cracks and deformation in the peripheral region 11B of the region 11A of the bonding sheet 11 using an ultrasonic imaging device FinSAT (FS300III) (manufactured by Hitachi Power Solutions). The measurements were performed using a probe with a frequency of 50 MHz, a gain of 30 dB, and a pitch of 0.2 mm, with the bonded structure (sample) placed in water.

[0195] (Discussion) From the results of the above Example II-1 and Comparative Example II-1, as well as the test results that the present inventors have conducted, it has been found that, in a joined body having a configuration in which the upper metal-containing member 12 and the lower metal-containing member 13 are joined to the front and back of the joining sheet 11, the area ratio of voids present in the region 11B of the joining sheet 11 (porosity X Ｂ ) is the area ratio of voids present in the region 11A (porosity X Ａ ) or the storage modulus Y at 200°C of the region 11B of the joining sheet 11 is made larger than Ｂ is the storage modulus Y at 200 ° C. of the region 11A Ａ It has been found that by making the thickness smaller than this, local pressure concentration in the region 11B of the bonding sheet 11 can be suppressed, and cracks and deformations in the region 11B can be eliminated during and after the manufacturing process of the bonded body.

[0196] <Examples and Comparative Examples of Joint III of the Present Invention> Example III-1 and Comparative Examples III-1 and III-2 of Joint III of the Present Invention will be described.

[0197] (Upper metal-containing member 22) Two upper metal-containing members 22 were prepared, each measuring 21 mm in length, 16 mm in width, and 5 mm in thickness, and each having a configuration in which the metal portion 221 was a copper plate measuring 16 mm in length, 13 mm in width, and 2 mm in thickness, except for the bottom surface, was covered with epoxy resin as resin 222.

[0198] (Lower Metal-Containing Member 23) As the lower metal-containing member 23, a copper plate having a length of 40 mm, a width of 80 mm, and a thickness of 2 mm was prepared.

[0199] (Joining sheet 21) High molecular weight epoxy resin (mass average molecular weight in polystyrene equivalent: 30,000, epoxy equivalent: 9,000 g / equivalent, density: approximately 1.2 g / cm ３ 9 parts by mass of a polyfunctional epoxy resin (molecular weight 500 or less, density approximately 1.2 g / cm) containing a structure having four or more glycidyl groups in one molecule ３ ) 7 parts by mass, biphenyl-type solid epoxy resin (molecular weight: about 400, density: about 1.2 g / cm ３) 15 parts by mass of spherical boron nitride agglomerated particles having a card house structure (average particle size (D50) 45 μm, maximum particle size (Dmax) 90 μm) 63 parts by mass of spherical boron nitride agglomerated particles having a card house structure (average particle size (D50) 45 μm, maximum particle size (Dmax) 90 μm), 5 parts by mass of a phenolic resin-based curing agent, 0.4 parts by mass of a curing catalyst (2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(17')]-ethyl-s-triazine, molecular weight: 247, properties: solid, melting point: 215-225 ° C), and 0.4 parts by mass of a curing catalyst (2-phenyl-4,5-dihydroxymethylimidazole, molecular weight: 204, properties: solid, melting point: dec. 230, so that the melting point is 230 ° C or higher), to which methyl ethyl ketone and cyclohexanone were added so that the solid content concentration was 74 mass%, and mixed using a planetary stirring device to prepare a slurry-like thermosetting resin composition.

[0200] The average particle diameter (D50) and maximum particle diameter (Dmax) of the boron nitride agglomerated particles are determined by dispersing the boron nitride agglomerated particles in a pure water medium containing sodium hexametaphosphate as a dispersion stabilizer, measuring the volumetric particle size distribution using a laser diffraction / scattering particle size distribution analyzer LA-300 (manufactured by Horiba, Ltd.), and determining the maximum particle diameter Dmax and the particle diameter at 50% cumulative volume (average particle diameter D50) from the obtained particle size distribution.

[0201] The thus obtained thermosetting resin composition in a slurry form was applied to a PET substrate by a doctor blade method, and the applied composition was dried by heating at 60°C (ambient temperature) for 120 minutes. Then, the applied composition was pressurized at 42°C (product temperature) and 1500 kgf / cm using a press. ２ The thermosetting sheet 21a was placed in a freezer at -20°C for 2 days without applying any weight, and subjected to low-temperature aging to obtain the thermosetting sheet 21a.

[0202] Example III-1 Using the above-described two upper metal-containing members 22, the lower metal-containing member 23, and the thermosetting sheet 21a, a bonded body was produced as follows.

[0203] A thermosetting sheet 21a was placed on the lower metal-containing member 23 to form a laminate, and copy paper was placed on the top and bottom of this laminate.Then, the laminate was set in a pressure press whose top and bottom top plates had been preheated to 80°C, and hot pressed at 80°C (product temperature) with a load of 2 MPa applied for 5 minutes. Next, two upper metal-containing members 22 were arranged side by side on the thermosetting sheet 21a with a distance of 15 mm between them to form a laminate, and copy paper was placed on the top and bottom of this laminate, and this was set in a pressure press whose top and bottom top plates had been preheated to 180°C, and hot-pressed at 180°C (product temperature) with a load of 6 MPa for 30 minutes, resulting in a bonded body having regions 21A and 21B, in which the two upper metal-containing members 22 were bonded to the front side of the 150 μm-thick bonding sheet 21 via 15 mm-wide blank portions 24, and a lower metal-containing member 23 was bonded to the back side of the bonding sheet 21, as shown in Figures 5 and 6.

[0204] When the cross sections of the region 21A and the region 21B of the bonding sheet 21 were observed using a scanning electron microscope (SEM), it was confirmed that there were voids in both the region 21A and the region 21B. Ａ is 137 μm, and the thickness T Ｂ is 156 μm, and the ratio of the two (T Ｂ / T Ａ ) is 1.14, and the difference between them (T Ｂ -T Ａ The thickness of the bonding sheet 21 was 19 μm. The BDV of the region 21A of the bonding sheet 21 was 5 kV or more. The thermal conductivity of the bonding sheet 21 in the thickness direction of the region 21A was 14 W / m·K.

[0205] Comparative Example III-1 A thermosetting sheet was obtained by aging the sheet in an environment at 100°C for 1 hour instead of the low-temperature aging in which the sheet was placed in a freezer at -20°C for 2 days in the preparation of the thermosetting sheet 21a. A bonded body was then prepared in the same manner as in Example III-1, except that the thermosetting sheet was used.

[0206] When the cross sections of the region 21A and the region 21B of the bonding sheet 21 were observed using a scanning electron microscope (SEM), it was confirmed that there were voids in both the region 21A and the region 21B. Ａ is 157 μm, and the thickness T Ｂ is 159 μm, and the ratio of the two (T Ｂ / T Ａ ) is 1.01, and the difference between them (T Ｂ -T Ａ ) was 2 μm. It was also confirmed that the BDV of the region 21A of the bonding sheet 21 was 1.5 kV (less than 5 kV).

[0207] Comparative Example III-2 A thermosetting sheet was obtained by aging the sheet in a 60°C environment for 3 days instead of the low-temperature aging in which the sheet was placed in a freezer at -20°C for 2 days in the preparation of the thermosetting sheet 21a. A bonded body was then prepared in the same manner as in Example III-1, except that the thermosetting sheet was used.

[0208] When the cross sections of the region 21A and the region 21B of the bonding sheet 21 were observed using a scanning electron microscope (SEM), it was confirmed that there were voids in both the region 21A and the region 21B. Ａ is 157 μm, and the thickness T Ｂ is 158 μm, and the ratio of the two (T Ｂ / T Ａ ) is 1.01, and the difference between them (T Ｂ -T Ａ ) was 1 μm. It was also confirmed that the BDV of the region 21A of the bonding sheet 21 was 1.5 kV (less than 5 kV).

[0209] <Methods for Measuring and Evaluating Physical Properties> The physical properties and evaluations of the bonded bodies produced in Example III-1 and Comparative Examples III-1 and III-2 were carried out as follows.

[0210] (Measurement of Thickness of Regions 21A and 21B) Appropriate locations of the regions 21A and 21B of the bonded bodies obtained in Example III-1 and Comparative Examples III-1 and III-2 were measured using a digital micrometer.

[0211] (Observation of voids) Appropriate locations of each of the regions 21A and 21B of the bonded bodies produced in Example III-1 and Comparative Examples III-1 to III-2 were cut in the thickness direction along the width direction (lateral direction) using a shearing process (DSW3500P (manufactured by Meiwafosis Co., Ltd.)). Cross-section processing was performed by subjecting arbitrary locations on the cut surfaces of each sheet to an ion milling process (Cross-section Polisher SM-09010 (manufactured by JEOL Ltd.)). The cross sections were observed using an SEM scanning electron microscope (SU5000 (manufactured by Hitachi Corporation)) at an acceleration voltage of 10 kV and a magnification of 300 times.

[0212] (Measurement of Breakdown Voltage (BDV)) The bonded bodies produced in Example III-1 and Comparative Examples III-1 to III-2 were immersed in Fluorinert FC-40 (manufactured by 3M), a voltage application jig was installed so that a voltage was applied between the metal part 221 of the upper metal-containing member 22 and the lower metal-containing member 23, and a voltage of 0.5 kV was applied to the region 21A of the bonding sheet 21 using an ultra-high voltage withstand voltage tester 7470 (manufactured by Keisoku Gijutsu Kenkyusho Co., Ltd.), and the voltage was increased by 0.5 kV every 60 seconds, and the breakdown voltage (BDV) was measured to confirm whether the breakdown voltage (BDV) was 5 kV or more.

[0213] (Measurement of thermal conductivity) A bonded sheet was produced under the same conditions as the bonded sheet 21 in the bonded body produced in Example III-1. That is, a portion of the thermosetting sheet 21a was heat-pressed at 80 ° C. (product temperature) under a load of 2 MPa for 5 minutes, and then heat-pressed at 180 ° C. (product temperature) under a load of 6 MPa for 30 minutes to produce a bonded sheet (measurement sample) having a region 21A that was pressurized twice. The thermal conductivity of the region 21A of the bonded sheet (measurement sample) was measured using a "T3ster DynTIM Tester" manufactured by Mentor Graphics. Two, three, or four bonded sheets (measurement samples) were stacked, and the thickness, area, and thermal resistance value of region 21A of four types of sheets with different thicknesses were measured. The thermal conductivity (25°C) in the sheet thickness direction using the steady-state method was calculated from the slope represented by the thermal resistance value versus sheet thickness (in accordance with ASTM D5470). The probe size during measurement was φ12.8 mm, the fixing pressure was 3400 kPa, and the measurement time was 300 seconds. Shin-Etsu Chemical Co., Ltd.'s "OIL COMPOUND (product name: G-747)" was used to improve adhesion between the sample and the probe.

[0214] (Discussion) From the results of the above Example III-1 and Comparative Examples III-1 to III-2, as well as the test results that the present inventors have conducted up to now, it has been found that by joining two or more upper metal-containing members 22 to the joining sheet 21 with a blank portion 24 between the adjacent upper metal-containing members 22, and by positioning the interface 22a between the upper metal-containing members 22 and the joining sheet 21 below the creeping surface 24a of the blank portion 24 to provide a step, the thickness T Ａ The thickness T of the region 21B of the joining sheet 21 that is not joined to the upper metal-containing member 22, i.e., the region 21B of the joining sheet 21 in the blank portion 24, is Ｂ The thickness T of the region 21A is preferably larger than the thickness T of the region 21A. Ａ The thickness T of the region 21B Ｂ The ratio (T Ｂ / T Ａ ) to 1.02 or more, (T Ｂ -T Ａ)×2, the current-carrying distance (creepage distance) between the metal portion of the upper metal-containing member 22 and the metal portion of the adjacent upper metal-containing member 22 can be increased.

[0215] If the electrical conduction distance (creepage distance) between the metal portion of one upper metal-containing member 22 and the metal portion of the adjacent upper metal-containing member 22 becomes short and creepage discharge occurs, the joining sheet 21 deteriorates, resulting in a decrease in the breakdown voltage (BDV). In contrast, as described above, by increasing the electrical conduction distance (creepage distance) between the metal portion of one upper metal-containing member 22 and the metal portion of the adjacent upper metal-containing member 22, the decrease in the breakdown voltage (BDV) can be suppressed.

[0216] Furthermore, since interface 22a between upper metal-containing member 22 and bonding sheet 21 is located below creeping surface 24a of gap 24, it is expected to reduce the risk of creeping discharge when current is applied to upper metal-containing member 22. Furthermore, for example, when used in a humid environment, the reach distance of moisture in the air when it penetrates into the bonding interface between the metal portion of upper metal-containing member 22 and bonding sheet 21 is increased, and since interface 22a between upper metal-containing member 22 and bonding sheet 21 is located below creeping surface 24a of gap 24, it is possible to reduce the risk of moisture absorption and to expect alleviating the cause of failure.

[0217] REFERENCE SIGNS LIST 1 Bonding sheet 1A Edge region 1B Central region 2 Upper metal-containing member 3 Lower metal-containing member 11 Bonding sheet 11A, 11B Region 12 Upper metal-containing member 13 Lower metal-containing member 14 Inorganic filler 15 Void 21 Bonding sheet 21A, 21B Region 22 Upper metal-containing member 22a Interface 23 Lower metal-containing member 24 Vacant portion 24a Creeping surface 25 Metal portion 26 Resin 27 Semiconductor chip 28 Wiring member 100 Bonding sheet 111 Inorganic filler 112 Void 121 Metal portion 122 Resin 123 Semiconductor chip 124 Wiring member 200 Upper metal-containing member 201 Metal portion 202 Resin 211 Inorganic filler 212 Void 221 Metal portion 222 Resin 223 Semiconductor chip 224 Wiring member 300 Lower metal-containing member

Claims

1. A joint body having a configuration in which an upper metal-containing member 2 and a lower metal-containing member 3 are joined to the front and back of a joint sheet 1, the upper metal-containing member 2 and the lower metal-containing member 3 each have a metal part on the joint surface with the joint sheet 1, the joint sheet 1 is a cured product of a thermosetting resin composition containing a thermosetting resin and an inorganic filler, the entire upper surface of the joint sheet 1 is joined to the upper metal-containing member 2, and the entire lower surface of the joint sheet 1 is joined to the lower metal-containing member 3, and when the joint sheet 1 is viewed in cross section, the resin area ratio in the end region 1A from the left or right end of the joint sheet 1 to the inside 300 μm is P １Ａ , the resin area ratio in the central region 1B other than the end region 1A is P １Ｂ Then, P １Ａ / P １Ｂ A joint body characterized in that the value of is greater than 1.

10.

2. A joint body having a configuration in which an upper metal-containing member 2 and a lower metal-containing member 3 are joined to the front and back of a joining sheet 1, the upper metal-containing member 2 and the lower metal-containing member 3 each have a metal part on the joining surface with the joining sheet 1, the joining sheet 1 is a cured product of a thermosetting resin composition containing a thermosetting resin and an inorganic filler, the entire upper surface of the joining sheet 1 is joined to the upper metal-containing member 2, and the entire lower surface of the joining sheet 1 is joined to the lower metal-containing member 3, and when the joining sheet 1 is viewed in cross section, the void area ratio in an end region 1A from one of the left and right ends of the joining sheet 1 to 300 μm inward is S １Ａ , the void area ratio in the central region 1B other than the end region 1A is S １Ｂ Then, S １Ａ / S １Ｂ A conjugate characterized in that the value of is greater than 1.

3. A joint body having a configuration in which an upper metal-containing member 2 and a lower metal-containing member 3 are joined to the front and back of a joint sheet 1, the upper metal-containing member 2 and the lower metal-containing member 3 each have a metal part on the joint surface with the joint sheet 1, the joint sheet 1 is a cured product of a thermosetting resin composition containing a thermosetting resin and an inorganic filler, the entire upper surface of the joint sheet 1 is joined to the upper metal-containing member 2, and the entire lower surface of the joint sheet 1 is joined to the lower metal-containing member 3, and when the joint sheet 1 is viewed in cross section, the average void size in the end region 1A from the left or right end of the joint sheet 1 to 300 μm inward is L １Ａ , the average void size in the central region 1B other than the end region 1A is L １Ｂ When this is done, L １Ａ / L １Ｂ A conjugate characterized in that the value of is greater than 2.

4. A joint described in any one of claims 1 to 3, having a configuration in which the joint sheet 1 and the upper metal-containing member 2 are directly joined, and the joint sheet 1 and the lower metal-containing member 3 are directly joined.

5. A joint described in any one of claims 1 to 3, in which the upper metal-containing member 2 has a sheet- or plate-shaped metal portion 25 with its underside exposed at the joint surface with the joint sheet 1, and the metal portion 25 is covered and sealed with resin 26.

6. A joint body as described in any one of claims 1 to 3, wherein the lower metal-containing member 3 has a flat or sheet-shaped metal body on the joint surface with the joint sheet 1.

7. A joint body according to any one of claims 1 to 3, characterized in that the thermal conductivity of the joint sheet 1 in the thickness direction is 10 W / m·K or more.

8. A joint body according to any one of claims 1 to 3, characterized in that the bonding sheet 1 has a dielectric breakdown voltage of 5 kV or more.

9. A joint according to any one of claims 1 to 3, wherein the metal portions of the upper metal-containing member 2 and the lower metal-containing member 3 are made of a material containing copper or aluminum.

10. The bonded body according to any one of claims 1 to 3, wherein the inorganic filler contained in the bonding sheet 1 includes agglomerated particles of boron nitride.

11. The joint of claim 10, wherein the boron nitride agglomerated particles have a house of cards structure.

12. A joint body according to any one of claims 1 to 3, wherein the thermosetting resin contained in the joint sheet 1 includes an epoxy resin.

13. A bonded body according to any one of claims 1 to 3, wherein the thickness of the bonding sheet 1 is 80 μm or more and 300 μm or less.

14. A bonding sheet which is a cured product of a thermosetting resin composition containing a thermosetting resin and an inorganic filler, and when the bonding sheet 1 is viewed in cross section, the resin area ratio in the end region 1A from the left or right end to the inside of 300 μm is P １Ａ , the resin area ratio in the central region 1B other than the end region 1A is P １Ｂ Then, P １Ａ / P １Ｂ The value of is greater than 1.10, and when the joining sheet 1 is viewed in cross section, the void area ratio in the end region 1A from the left or right end to the inside 300 μm is S １Ａ , the void area ratio in the central region 1B other than the end region 1A is S １Ｂ Then, S １Ａ / S １Ｂ The value of is greater than 1, and when the joining sheet 1 is viewed in cross section, the average void size in the end region 1A from the left or right end of the joining sheet 1 to the inside by 300 μm is L １Ａ , the average void size in the central region 1B other than the end region 1A is L １Ｂ When this is done, L １Ａ / L １Ｂ A bonding sheet characterized in that the value of is greater than 2.

15. A method for producing a joint as described in any one of claims 1 to 3, comprising the steps of: overlaying a thermosetting sheet obtained by molding the thermosetting resin composition into a sheet shape on a lower metal-containing member 3; applying uniform pressure to bond the lower metal-containing member 3 and the thermosetting sheet together; and then overlaying an upper metal-containing member 2 on the thermosetting sheet; and applying uniform pressure to bond the thermosetting sheet and the upper metal-containing member 2 together.

16. The method for producing a joint body according to claim 15, wherein the thermosetting sheet is subjected to low-temperature aging in an environment of -50°C or higher and 0°C or lower before being placed on the lower metal-containing member 3.

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