Joined body

Abstract

To provide a joined body having a configuration in which an upper member 2 and a lower member 3 are joined to front and back surfaces of a joining sheet 1, the upper member 2 having a Sn-plated layer 2A on the joining surface, the lower member 3 having a Ni-plated layer 3A on the joining surface, where the joined body is capable of suppressing a decrease in adhesiveness due to temperature changes, particularly suppressing a decrease in adhesiveness between the upper member 2 provided with the Sn-plated layer 2A and the joining sheet 1, and also suppressing a decrease in insulation properties.SOLUTION: A joined body is formed such that an area A of the Sn-plated layer 2A of the upper member 2 and an area B of the Ni-plated layer 3A of the lower member 3 satisfy a relationship of (area A)<(area B).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a joined body, such as a power semiconductor module, having a configuration in which an upper member and a lower member are joined to the front and back of a joining sheet. [Background technology]

[0002] Among devices using semiconductors, devices that control and convert power from a power supply, etc., are called power semiconductor devices. A power semiconductor module equipped with electronic components is known to have a configuration in which electronic components such as semiconductor elements are placed in the center of the upper surface of a metal base plate (heat sink) via an insulating substrate, and a heat dissipation member such as a metal member is placed on top of the electrical components, and these electronic components and heat dissipation member are enclosed and sealed with synthetic resin (see Patent Documents 1 to 3).

[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 4 discloses a heat-dissipating resin sheet containing an epoxy resin and a boron nitride filler, in which the content of the boron nitride filler is 30 vol% or more and 60 vol% or less, and the Tg of the resin is 60°C or less. Patent Document 5 also discloses a heat dissipation sheet containing an aggregated inorganic filler and a resin, in which the aggregated inorganic filler has a breaking strength of 20 MPa or less and an elastic modulus of 48 MPa or more. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-323593 [Patent Document 2] International Publication No. 2016 / 162991 [Patent Document 3] Japanese Patent Application Publication No. 2018-74089 [Patent Document 4] Japanese Patent Application Laid-Open No. 2017-036415 [Patent Document 5] International Publication No. 2019 / 189746 Summary of the Invention [Problem to be solved by the invention]

[0006] In semiconductor packages such as power semiconductor modules, plating is sometimes applied to the wiring portion of the substrate or the lead frame to ensure wire bonding properties, solderability, corrosion resistance, etc. For this reason, a bonded body is used in which a semiconductor package substrate (corresponding to "upper member 2" in the present invention) with a plated copper plate laminated on the underside and a base plate (corresponding to "lower member 3" in the present invention) made of a plated copper plate are bonded via an insulating substrate (corresponding to "bonding sheet 1" in the present invention) whose main materials are a thermosetting compound and an inorganic filler. In a joint structure of this type, if the joint surface of the upper member 2, which is directly joined to the joint sheet 1, and the joint surface of the lower member 3 are plated with different metals, for example, if one is a Ni-plated layer and the other is a Sn-plated layer, the adhesion will decrease due to temperature changes during use, and in particular, the adhesion between the upper member 2 having the Sn-plated layer and the joint sheet 1 will decrease, and the insulating properties of the joint will also decrease, resulting in problems such as a loss of long-term reliability (TCT).

[0007] Therefore, the object of the present invention is to provide a joined body having a configuration in which an upper member 2 and a lower member 3 are joined to the front and back of a joining sheet 1, where the joining surface of the upper member 2 has a Sn-plated layer and the joining surface of the lower member 3 has a Ni-plated layer, which can suppress a decrease in adhesion due to temperature changes, particularly a decrease in adhesion between the upper member 2 having the Sn-plated layer and the joining sheet 1, and can also suppress a decrease in insulation. [Means for solving the problem]

[0008] In order to solve the above problems, the bonded body proposed by the present invention has the following configuration.

[0009] [1] The first aspect of the present invention is a joined body having a configuration in which an upper member 2 and a lower member 3 are directly joined to the front and back of a joining sheet 1, The upper member 2 has a Sn plating layer 2A mainly made of tin or a tin alloy on its lower surface, i.e., the joining surface, and the lower member 3 has a Ni plating layer 3A mainly made of nickel or a nickel alloy on its upper surface, i.e., the joining surface. The bonding sheet 1 is a cured product of a thermosetting resin composition containing a thermosetting resin and an inorganic filler, In this joined body, the area A of the Sn plated layer 2A of the upper member 2 and the area B of the Ni plated layer 3A of the lower member 3 satisfy the relationship area A<area B.

[0010] [2] A second aspect of the present invention is the first aspect, This bonded body has a value of (shear strength MPa of the bonded body before the heat cycle test described below / shear strength MPa of the bonded body after the heat cycle test described below) × (elastic modulus of the bonding sheet 1 at 25°C GPa−elastic modulus of the bonding sheet 1 at 200°C GPa) × (average linear expansion coefficient of the bonding sheet 1 in a temperature range of 25°C to 200°C ppm / K−average linear expansion coefficient of copper ppm / K) × (water droplet contact angle of the bonding sheet 1 in degrees) ÷ (thickness of the bonding sheet 1 in μm) that is 0.15 or more and 7500 or less ((GPa×°) / (m×K))). Thermal cycle test: The bonded body is subjected to a cycle of 30 minutes at -40°C, 1 minute at 25°C, and 30 minutes at 150°C, and the cycle is repeated up to 1000 times. Shear strength: The shear strength (MPa) of the bonded body is measured in accordance with JIS K 6254.

[0011] [3] A third aspect of the present invention is the bonded body of the first or second aspect, wherein the average linear expansion coefficient of the bonding sheet 1 in the temperature range of 25°C to 200°C is 20 ppm / K to 80 ppm / K.

[0012] [4] A fourth aspect of the present invention is a joined body according to any one of the first to third aspects, wherein the ratio (B / A) of the area B of the Ni-plated layer 3A of the lower member 3 to the area A of the Sn-plated layer 2A of the upper member 2 is 1.5 or more and 500 or less.

[0013] [5] A fifth aspect of the present invention is the bonded body according to any one of the first to fourth aspects, wherein the inorganic filler contained in bonding sheet 1 includes agglomerated particles of boron nitride. [6] A sixth aspect of the present invention is the bonded body according to any one of the first to fifth aspects, wherein the thermosetting resin contained in bonding sheet 1 includes an epoxy resin. [7] A seventh aspect of the present invention is the bonded body according to any one of the first to sixth aspects, wherein the thickness of the bonding sheet 1 is 80 μm or more and 300 μm or less.

[0014] [8] An eighth aspect of the present invention is any one of the first to seventh aspects, wherein the upper member 2 has a Sn-plated layer 2A on the lower surface of a metal member 2B mainly made of copper, The lower member 3 is a joined body in which a Ni-plated layer 3A is provided on the upper surface of a metal member 3B made mainly of copper.

[0015] [9] A ninth aspect of the present invention is any one of the first to eighth aspects, wherein the area A of the Sn plating layer 2A of the upper member 2 is 0.25 cm 2 More than 50cm 2The area B of the Ni plating layer 3A of the lower member 3 is 0.4 cm 2 More than 600cm 2 The following is a zygote. [Effects of the Invention]

[0016] The bonded structure proposed by the present invention is a bonded structure in which an upper member 2 having a Sn-plated layer 2A on its bonding surface and a lower member 3 having a Ni-plated layer 3A on its bonding surface are bonded to the front and back of a bonding sheet 1. By making the area A of the Sn-plated layer 2A, which has a large linear expansion coefficient, smaller than the area B of the Ni-plated layer 3A, which has a small linear expansion coefficient, it is possible to suppress a decrease in adhesion due to temperature changes, particularly a decrease in adhesion between the upper member 2 having the Sn-plated layer 2A and the bonding sheet 1, and it is also possible to suppress a decrease in insulation, thereby maintaining long-term reliability (TCT). [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a diagram schematically illustrating a cross section (in the thickness direction) of a bonded body as an example of the present invention. [Figure 2] FIG. 2 is a diagram schematically illustrating a cross section (in the thickness direction) of a bonded body as another example of the present invention. [Figure 3] FIG. 2 is a diagram schematically illustrating a cross section (in the thickness direction) of a bonded body as another example of the present invention. [Figure 4] FIG. 1 is a diagram showing a schematic diagram of a shear test method. [Figure 5] FIG. 1 is a diagram showing a schematic diagram of a method for measuring a breakdown voltage. DETAILED DESCRIPTION OF THE INVENTION

[0018] 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.

[0019] <<Conjugate of the present invention>> 1 and 2, a bonded structure according to one embodiment of the present invention (also referred to as the "bonded structure of the present invention") is a bonded structure having an upper member 2 and a lower member 3 directly bonded to the front and back of a bonded sheet 1. That is, the bonded structure has an upper member 2 directly bonded to the upper surface of the bonded sheet 1, and a lower member 3 directly bonded to the lower surface of the bonded sheet 1. Here, the above-mentioned "directly bonded" means that the bonding sheet 1, the upper member 2, and the lower member 3 are bonded without any other layer or member such as an adhesive layer interposed therebetween.

[0020] The upper member 2 has a Sn-plated layer 2A mainly made of tin or a tin alloy on its lower surface, i.e., the surface where it joins with the joining sheet 1, and the lower member 3 has a Ni-plated layer 3A mainly made of nickel or a nickel alloy on its upper surface, i.e., the surface where it joins 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, and the joining sheet 1 is bonded to the upper member 2 and the lower member 3 by the thermosetting resin. Next, each member will be described in detail.

[0021] <Upper member 2> The upper member 2 may be any member provided with a Sn-plated layer 2A mainly made of tin or a tin alloy on the lower surface, ie, the surface to be joined with the joining sheet 1, of a metal member 2B such as a metal sheet or metal plate. For example, as shown in Fig. 1, the entire lower surface of the upper member 2 may be configured to be a Sn-plated layer 2A, or as shown in Fig. 2, the lower surface of the upper member 2 may be configured to be a Sn-plated layer 2A on a portion thereof, the periphery of which is covered and sealed with resin 23. Other configurations are also possible.

[0022] The metal member 2B may be in the shape of a plate, a sheet, or any other shape. The metal member 2B is preferably made primarily of a material with good thermal conductivity. Among these, those made primarily of copper or aluminum are preferred because they have good thermal conductivity and are relatively inexpensive. Of these, those made primarily of copper are more preferred from the viewpoint of heat dissipation. Here, "main material" means the material with the highest mass percentage among the materials constituting the metal member 2B, and can be considered to be a material that accounts for 50 mass% or more of the metal member 2B, particularly 70 mass% or more, particularly 90 mass% or more, and particularly 100 mass%.

[0023] The resin that seals the metal member 2B may be, for example, a resin with insulating properties. Examples of insulating resins include epoxy resin, vinyl chloride resin, acrylic resin, polypropylene, polyethylene, nylon, polycarbonate, phenol resin, polyarylate, benzoxazine, and cyanate.

[0024] As an example of the upper member 2, as shown in FIG. 3, a module configuration can be given in which a semiconductor chip 21 is mounted on a metal member 2B as a heat dissipation member, a wiring member 22 is wired on the metal member 2B, and the metal member 2B and the semiconductor chip 21 are covered and sealed with insulating resin 23.

[0025] The metal member 2B preferably has an average linear expansion coefficient in the temperature range of 25°C or higher and 200°C or lower of 10 ppm / K or higher and 30 ppm / K or lower. Furthermore, in the temperature range of 25° C. or higher and 200° C. or lower, the difference in average linear expansion coefficient between the joining sheet 1 and the Sn plating layer 2A is preferably 0 ppm / K or higher and 60 ppm / K or lower.

[0026] A mechanically bonded state may be formed on the lower surface of the upper member 2 by forming minute irregularities by etching, blasting, etc. However, a feature of the present invention is that adhesiveness can be maintained even without forming such a mechanically bonded state. The lower surface of the upper component 2 may be treated with a coupling agent or a primer, etc. Even if the lower surface of the upper component 2 has been treated with a coupling agent or a primer, it still falls under the category of "directly bonded" above.

[0027] From the viewpoint of durability, the thickness of the Sn plating layer 2A is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 1 μm or more, while from the viewpoint of warpage, the thickness is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 10 μm or less. From the viewpoint of heat dissipation, the thickness of the metal member 2B is preferably 0.1 mm or more, more preferably 0.5 mm or more, and even more preferably 1 mm or more, while from the viewpoint of warping, the thickness is preferably 10 mm or less, more preferably 5 mm or less, and even more preferably 3 mm or less.

[0028] <Lower member 3> As shown in Figures 1 to 3, the lower member 3 may be a metal member 3B in the form of a flat metal plate or metal sheet, and provided with a Ni plating layer 3A mainly made of nickel or a nickel alloy on the upper surface, i.e., the joining surface with the joining sheet 1.

[0029] The metal member 3B in the form of a metal plate or metal sheet is preferably made primarily of a material with good thermal conductivity. Among these, those made primarily of copper or aluminum are preferred because they have good thermal conductivity and are relatively inexpensive. Of these, those made primarily of copper are more preferred from the viewpoint of heat dissipation. Here, "main material" means the material with the highest mass percentage among the materials constituting the metal member 3B, and can be considered to be a material that accounts for 50 mass% or more of the metal member 3B, particularly 70 mass% or more, particularly 90 mass% or more, and particularly 100 mass%.

[0030] The metal member 3B preferably has an average linear expansion coefficient in the temperature range of 25°C or higher and 200°C or lower of 10 ppm / K or higher and 30 ppm / K or lower.

[0031] A mechanically bonded state may be formed on the upper surface of the lower member 3 by forming fine irregularities by etching, blasting, etc. However, a feature of the present invention is that adhesiveness can be maintained even without forming such a mechanically bonded state. The upper surface of the lower component 3 may be treated with a coupling agent or a primer, etc. Even if the upper surface of the lower component 3 has been treated with a coupling agent or a primer, it falls under the category of "directly bonded" above.

[0032] From the viewpoint of durability, the thickness of the Ni plating layer 3A is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 1 μm or more, and from the viewpoint of warpage, it is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 10 μm or less. From the viewpoint of heat dissipation, the thickness of the metal member 3B is preferably 0.1 mm or more, more preferably 0.5 mm or more, and even more preferably 1 mm or more, while from the viewpoint of warping, the thickness is preferably 10 mm or less, more preferably 5 mm or less, and even more preferably 3 mm or less.

[0033] <Area A of the Sn-plated layer 2A of the upper member 2 and Area B of the Ni-plated layer 3A of the lower member 3> In the joined body of the present invention, the area A of the Sn-plated layer 2A of the upper member 2 and the area B of the Ni-plated layer 3A of the lower member 3 preferably satisfy the relationship area A<area B. By making the area A of the Sn plating layer 2A, which has a large linear expansion coefficient, smaller than the area B of the Ni plating layer 3A, which has a small linear expansion coefficient, it is possible to suppress a decrease in adhesion due to temperature changes, particularly a decrease in adhesion between the upper member 2 having the Sn plating layer 2A and the joining sheet 1, and it is also possible to suppress a decrease in insulation, thereby maintaining long-term reliability (TCT). From this viewpoint, it is more preferable that the ratio (B / A) of the area B of the Ni plated layer 3A of the lower member 3 to the area A of the Sn plated layer 2A of the upper member 2 is 1.5 or more, and even more preferable that it is 3 or more, more preferably 5 or more, and even more preferably 10 or more. On the other hand, from the viewpoint of the occupied area, the ratio (B / A) is more preferably 500 or less, more preferably 100 or less, even more preferably 50 or less, and even more preferably 30 or less.

[0034] The area A of the Sn plating layer 2A of the upper member 2 is set to 0.25 cm from the viewpoint of heat dissipation. 2 It is preferable that the thickness is 1 cm or more, and especially 1 cm 2 Above all, 2cm 2 Above all, 3cm 2 On the other hand, from the viewpoint of warping, it is more preferable that the thickness is 50 cm or more. 2 Preferably it is less than 30cm 2 Below, among them, 20cm 2 Below, among them, 10cm 2 More preferably, it is:

[0035] The area B of the Ni plating layer 3A of the lower member 3 is set to 0.4 cm 2 It is preferable that the thickness is 2 cm or more. 2 Above all, 4cm 2 Above all, 6cm 2 On the other hand, from the viewpoint of the occupied area, it is more preferable that the 2 It is preferable that the distance is less than 400 cm 2 Below, among them, 200cm 2 Below, among them, 100cm 2 More preferably, it is:

[0036] As shown in FIG. 2, when multiple upper components 2 are joined to the upper surface of the joining sheet 1, the area A of the Sn-plated layer 2A described above is not the total of the multiple upper components 2, but the area A of the Sn-plated layer 2A of each upper component 2. Even when multiple lower components 3 are joined to the lower surface of the joining sheet 1, the area B of the Ni plating layer 3A described above is not the total of the multiple lower components 3, but the area B of the Ni plating layer 3A of each lower component 3.

[0037] As an example of the bonded structure of the present invention, as shown in Figures 1 to 3, the entire lower surface of the upper member 2 is bonded to part or the entire upper surface of the bonding sheet 1, and the entire lower surface of the bonding sheet 1 is bonded to part or the entire upper surface of the lower member 3. As shown in FIG. 1, in the case where the entire lower surface of the bonding sheet 1 is bonded to a part of the upper surface of the lower member 3, the area B of the Ni plating layer 3A of the lower member 3 is not the adhesive area between the bonding sheet 1 and the Ni plating layer 3A of the lower member 3, but the area B of the Ni plating layer 3A of the lower member 3 itself.

[0038] <Bonding sheet 1> The bonding sheet 1 contains an inorganic filler and a cured product of a thermosetting resin. In other words, the bonding sheet 1 is a cured product of a thermosetting sheet (hereinafter referred to as "the present thermosetting sheet") obtained by forming a thermosetting resin composition (hereinafter referred to as "the present thermosetting resin composition") containing a thermosetting resin and an inorganic filler into a sheet shape.

[0039] 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, it is sufficient if the resin composition has the curability to be cured by heat, and may be one that has already been cured to a state where there is still room for curing (also referred to as "temporarily 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 hardened by heat. That is, it is sufficient if the sheet has the hardening property to allow room for hardening by heat, and it may be one that has already been hardened to a state where room for hardening remains (also referred to as "pre-hardened"), or one that has not yet been hardened at all (referred to as "unhardened").

[0040] (This thermosetting resin composition) The present thermosetting resin composition is a composition containing a thermosetting resin and an inorganic filler, and can be formed into a sheet to form the present thermosetting sheet.

[0041] As the thermosetting resin, conventionally known resins can be used. Examples include epoxy resins, phenolic resins, urea resins, melamine resins, polyester (e.g., unsaturated polyester) resins, polyimide resins, silicone resins, polyurethane resins, maleimide resins, cyanate resins, and benzoxazine. The thermosetting resin can be a mixture of one or more of these resins.

[0042] As the inorganic filler, conventionally known inorganic fillers can be used. For example, nitrides such as boron nitride and metal oxides such as alumina can be used. Note that the inorganic filler can be used alone or in combination of two or more of these inorganic fillers.

[0043] The content of the thermosetting resin is preferably 5 to 99 mass % relative to 100 mass % of the total solid content of the present thermosetting resin composition excluding the inorganic filler. A thermosetting resin content of 5% by mass or more is preferable because it provides good moldability, while a content of 99% by mass or less is preferable because it ensures the content of other components and increases thermal conductivity. From this viewpoint, the content of the thermosetting resin is more preferably 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, based on 100% by mass of the total solid content of the thermosetting resin composition excluding the inorganic filler, while it is even more preferably 98% by mass or less.

[0044] The total content of the inorganic filler is preferably 40% by mass or more and 90% by mass or less, relative to 100% by mass of the total solid content of the present thermosetting resin composition. If the total content of the inorganic filler is 40% by mass or more, the thermal conductivity can be increased, while if it is 90% by mass or less, the adhesion and insulating properties can be increased. From this viewpoint, the total content of the inorganic filler is preferably 50% by mass or more, more preferably 53% by mass or more, and even more preferably 55% by mass or more, based on 100% by mass of the total solid content of the thermosetting resin composition, and is preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 72% by mass or less.

[0045] Among these, it is preferable to include an epoxy resin as the thermosetting resin, and it is preferable to include, as the inorganic filler, boron nitride agglomerated particles formed by agglomeration of primary particles made of boron nitride, from the viewpoints of water resistance and low dielectric constant. Among these, it is preferable to include, as the boron nitride agglomerated particles, boron nitride agglomerated particles having a house-of-card structure, and it is preferable that they are spherical in shape, from the viewpoints of high thermal conductivity and high withstand voltage. 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 solid content of the thermosetting resin composition.

[0046] The present thermosetting resin composition 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.

[0047] <Physical properties of bonding sheet 1> The bonding sheet 1 can have the following physical properties.

[0048] (Thickness) The thickness of the bonding sheet 1 is not particularly limited. When the bonded body of the present invention is used in, for example, a power semiconductor device, industrial equipment, an in-vehicle device, or a power generating energy device, 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 be ensured but also sufficient voltage resistance can be ensured. On the other hand, by making the thickness 300 μm or less, the bonded body of the present invention can be made smaller or thinner, and the thinner film can have the effect of reducing thermal resistance in the thickness direction compared to an insulating thermally conductive layer made of a ceramic material.

[0049] (elastic modulus) The bonding sheet 1 preferably has an elastic modulus of the bonding sheet 1 at 25° C. (GPa)−elastic modulus of the bonding sheet 1 at 200° C. (GPa) of 0.5 GPa or more and 20 GPa or less. The bonding sheet 1 has better adhesiveness when its modulus of elasticity at high temperatures is higher, so it is preferable that the difference in modulus of elasticity between 25°C and 200°C is small. From this viewpoint, the elastic modulus of the bonding sheet 1 (at 25°C (GPa) minus the elastic modulus of the bonding sheet 1 (GPa) at 200°C) is preferably 20 GPa or less, more preferably 18 GPa or less, and even more preferably 15 GPa or less. On the other hand, it is preferably 0.5 GPa or more, and even more preferably 1 GPa or more. In order for the bonding sheet 1 to have the above-mentioned elastic modulus, for example, the crosslink density may be increased to prevent the elastic modulus from decreasing at high temperatures, but the method is not limited to this. Regarding the method for measuring the elastic modulus of the bonding sheet 1, please refer to the measurement method in the examples.

[0050] (coefficient of linear expansion) The bonding sheet 1 preferably has an average linear expansion coefficient of bonding sheet 1 ppm / K - average linear expansion coefficient of copper ppm / K) of 2 ppm / K to 62 ppm / K in the temperature range of 25°C to 200°C. The bonding sheet 1 has better adhesion if its linear expansion coefficient is closer to that of copper, a typical example of the material constituting the metal member 2B of the upper member 2 or the metal member 3B of the lower member 3. Therefore, it is preferable that the difference between the average linear expansion coefficient of the bonding sheet 1 in the temperature range of 25°C or higher and 200°C or lower and the average linear expansion coefficient of copper in the temperature range of 25°C or higher and 200°C or lower is small. From this viewpoint, the bonding sheet 1 has a (average linear expansion coefficient of bonding sheet 1 ppm / K - average linear expansion coefficient of copper ppm / K) of preferably 62 ppm / K or less, more preferably 40 ppm / K or less, and even more preferably 30 ppm / K or less, in the temperature range of 25°C to 200°C. On the other hand, it is preferably 2 ppm / K or more, more preferably 3 ppm / K or more, and even more preferably 5 ppm / K or more. The relationship with the linear expansion coefficient of copper is specified assuming that the metal member 3B of the lower member 3 is made of copper.

[0051] The bonding sheet 1 preferably has an average linear expansion coefficient of 20 ppm / K or more and 80 ppm / K or less in the temperature range of 25°C or more and 200°C or less. The average linear expansion coefficient of the bonding sheet 1 in the temperature range of 25° C. to 200° C. is preferably 20 ppm / K or more from the viewpoint of warping, and 80 ppm / K or less from the viewpoint of reverse warping. From this viewpoint, the average linear expansion coefficient of the bonding sheet 1 in the temperature range of 25°C to 200°C is preferably 20 ppm / K or more, more preferably 21 ppm / K or more, and even more preferably 22 ppm / K or more. On the other hand, it is preferably 80 ppm / K or less, more preferably 60 ppm / K or less, and even more preferably 40 ppm / K or less.

[0052] In order for the bonding sheet 1 to have the above-mentioned linear expansion coefficient, for example, the crosslink density may be increased or an inorganic filler may be contained, but the bonding sheet 1 is not limited to these methods. Regarding the method for measuring the linear expansion coefficient of the bonding sheet 1, please refer to the measurement method in the examples.

[0053] (Water droplet contact angle) The bonding sheet 1 preferably has a water droplet contact angle (°) of 50° or more and 120° or less. A water droplet contact angle of 50° or more is preferable because it can prevent a decrease in adhesiveness due to moisture absorption, whereas a water droplet contact angle of 120° or less is preferable because it can prevent a decrease in adhesiveness without reducing the cohesive force with the metal surface. From this viewpoint, the water droplet contact angle of the bonding sheet 1 is preferably 50° or more, more preferably 60° or more, and even more preferably 70° or more. On the other hand, it is preferably 120° or less, more preferably 110° or less, and even more preferably 100° or less.

[0054] In order for the bonding sheet 1 to have the water droplet contact angle described above, for example, a hydrophobic resin may be used as the thermosetting resin constituting the bonding sheet 1. Examples of the hydrophobic resin include epoxy resins such as bisphenol-type epoxy compounds obtained by glycidylating bisphenols, biphenyl-type epoxy compounds, epoxy compounds obtained by glycidylating dihydric phenols, novolac-type epoxy compounds obtained by glycidylating novolacs, epoxy compounds having a dicyclopentadiene skeleton, and epoxy compounds having a naphthalene skeleton, polyether ether ketone resins, and silicone resins. Preferably, an epoxy resin with a molecular weight of 10,000 or more can be used. However, the method is not limited to this. Regarding the method for measuring the water droplet contact angle of the bonding sheet 1, please refer to the measurement method in the examples.

[0055] (thermal conductivity) When the bonded structure of the present invention is used for applications such as power semiconductor devices, industrial equipment, automotive equipment, and energy generation, the thermal conductivity of the bonding sheet 1 in the bonded structure of the present invention, i.e., the bonding sheet 1 bonding both the upper member 2 and the lower member 3, in the thickness direction 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.

[0056] The thermal conductivity of the bonding sheet 1 can be adjusted as described above by overlapping the upper member 2 and the lower member 3 on the front and back of the thermosetting sheet, applying pressure to the bonding sheet 1, and thermally curing the thermosetting sheet, as described below, by adjusting the pressure conditions, the type of thermosetting resin, the type and content of the inorganic filler, the presence or absence of aging and the conditions for aging, etc. However, the method is not limited to this. Regarding the method for measuring the thermal conductivity in the thickness direction of the bonding sheet 1, please refer to the measurement method in the examples.

[0057] (Breakdown voltage (BDV)) When the bonded structure of the present invention is used for applications such as power semiconductor devices, industrial equipment, automotive equipment, and energy generation, the breakdown voltage of the bonding sheet 1 in the bonded structure of the present invention, i.e., the bonding sheet 1 bonding both the upper member 2 and the lower 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.

[0058] The breakdown voltage of the bonding sheet 1 can be adjusted to the above range by, in a method described below in which the upper member 2 and the lower member 3 are placed on the front and back of the thermosetting sheet, pressurizing the bonding sheet 1, and thermally curing the thermosetting sheet, adjusting the pressure conditions, the type of thermosetting resin, the type and content of the inorganic filler, whether or not aging is performed, and the conditions for aging, etc. However, the method is not limited to this. Regarding the method for measuring the breakdown voltage of the bonding sheet 1, please refer to the measurement method in the examples.

[0059] <Conjugate of the Present Invention> The bonded body of the present invention may have the following physical properties.

[0060] (shear strength) The bonded body of the present invention preferably has a ratio (shear strength MPa of bonded body before the below-described heat cycle test / shear strength MPa of bonded body after the below-described heat cycle test) of 0.5 to 4.0. The higher the shear strength of the bonded body after the thermal cycle test, the more reliable it is, so it is preferable that the ratio (shear strength of the bonded body before the thermal cycle test / shear strength of the bonded body after the thermal cycle test) is small. From this viewpoint, the shear strength MPa of the bonded body before the thermal cycle test described below / shear strength MPa of the bonded body after the thermal cycle test described below is preferably 4.0 or less, more preferably 3.5 or less, and even more preferably 3.0 or less, and on the other hand, it is preferably 0.5 or more, more preferably 1.0 or more, and even more preferably 1.2 or more.

[0061] Thermal cycle test: As in the examples, the bonded body is subjected to 1000 cycles, with one cycle consisting of 30 minutes at -40°C, 1 minute at 25°C, and 30 minutes at 150°C. Shear strength: The shear strength (MPa) of the bonded structure is measured in accordance with JIS K 6254. More specifically, in accordance with JIS K 6254, the strength of the force when the upper member 2 is peeled off from the bonded structure is divided by the area of ​​the adhesive surface between the bonded sheet 1 and the upper member 2, and the value is measured as the shear strength (MPa).

[0062] (Composite physical properties) The bonded body of the present invention preferably has a value of (shear strength MPa of bonded body before the heat cycle test described below / shear strength MPa of bonded body after the heat cycle test described below) × (elastic modulus of bonding sheet 1 at 25°C GPa−elastic modulus of bonding sheet 1 at 200°C GPa) × (average linear expansion coefficient of bonding sheet 1 ppm / K in a temperature range of 25°C to 200°C−average linear expansion coefficient of copper ppm / K) × (water droplet contact angle of bonding sheet 1 °) ÷ (thickness of bonding sheet 1 μm) of 0.15 to 7500 ((GPa×°) / (m×K)). Thermal cycle test: The bonded body is subjected to a cycle of 30 minutes at -40°C, 1 minute at 25°C, and 30 minutes at 150°C, and the cycle is repeated up to 1000 times. Shear strength: The shear strength (MPa) of the bonded body is measured in accordance with JIS K 6254.

[0063] It is preferable if the value of the above "(shear strength MPa of the bonded body before the heat cycle test described below / shear strength MPa of the bonded body after the heat cycle test described below) × (elastic modulus of the bonding sheet 1 at 25°C GPa - elastic modulus of the bonding sheet 1 at 200°C GPa) × (average linear expansion coefficient of the bonding sheet 1 in the temperature range of 25°C to 200°C ppm / K - average linear expansion coefficient of copper ppm / K) × (water droplet contact angle of the bonding sheet 1 in degrees) ÷ (thickness of the bonding sheet 1 in μm)") is 0.15 or more and 7500 or less ((GPa × °) / (m × K))), because stress during bonding can be suppressed. From this viewpoint, the value is preferably 0.15 or more, more preferably 10 or more, and even more preferably 100 or more. On the other hand, the value is preferably 7500 or less, more preferably 5000 or less, and even more preferably 2000 or less.

[0064] <Method of manufacturing the bonded body of the present invention> Next, a method for producing the bonded body of the present invention will be described. A method for producing the bonded body of the present invention includes placing the thermosetting sheet between the upper member 2 and the lower member 3 and controlling the pressing conditions such as the pressing pressure, pressing temperature, and pressing configuration. The method described below is merely an example of a method for producing a bonded body of the present invention, and is not limited to the following method.

[0065] First, it is preferable to place the thermosetting sheet on the lower member 3 and apply a uniform pressure (first pressure application) to bond them together. 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 make the pressure uniform.

[0066] The first pressurization is sufficient if it is possible to temporarily fix the bonding sheet 1 onto the lower member 3, so it is preferable to apply pressure to the bonding sheet 1 at a pressure of 0.5 MPa or more and 10 MPa or less, and it is even more preferable to apply pressure at a pressure of 1 MPa or more or 9 MPa or less, and of these, 2 MPa or more or 8 MPa or less. The first pressurization may be performed simultaneously with heating. The heating 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 120°C or lower, more preferably 100°C or lower, and even more preferably 90°C or lower.

[0067] Next, it is preferable to place the upper member 2 on the thermosetting sheet and apply uniform pressure (second pressurization) to bond them together. That is, pressure is applied to the region 1A of the joining sheet 1 that overlaps both the upper member 2 and the lower member 3 when viewed in cross section, and the entire thermosetting sheet is heated to thermally cure it, thereby joining the upper member 2 and the lower member 3 to the front and back of the joining sheet 1, thereby producing the joined body of the present invention. In this case, a plurality of upper members 2 may be attached in the form of a sheet. 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.

[0068] The second pressurization improves contact between the inorganic fillers, facilitating the formation of heat conduction paths and improving thermal conductivity. From this viewpoint, it is desirable to apply a pressure of 2 MPa or more in the second pressurization. The pressure is preferably 4 MPa or more, more preferably 5 MPa or more, and even more preferably 6 MPa or more, and is preferably 150 MPa or less, more preferably 100 MPa or less, and even more preferably 20 MPa or less.

[0069] The second pressurization and heating may be carried out simultaneously. The heating temperature at this time is preferably 120° C. or higher, more preferably 150° C. or higher, and even more preferably 170° 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.

[0070] As a specific example, pressing and heating can be performed simultaneously by preheating the upper and lower top plates of a pressure press, placing the upper member 2 on the thermosetting sheet that is placed on the lower member 3 to form a laminate, and then setting this laminate in the pressure press and applying pressure between the upper and lower top plates. Alternatively, pressing and heating can be performed simultaneously by placing the thermosetting sheet on the lower member 3, placing the upper member 2 on the thermosetting sheet, and then heating the pressure press or its press unit to apply pressure. In this case, both regions 1A and 1B of the bonded sheet 1 are heated.

[0071] The pressurization time is not particularly limited. The first pressurization and the second and subsequent pressurizations are each preferably 30 seconds or longer, more preferably 1 minute or longer, even more preferably 3 minutes or longer, and particularly preferably 5 minutes or longer. The pressurization step time is preferably 1 hour or shorter, more preferably 30 minutes or shorter, and even more preferably 20 minutes or shorter. When the pressurizing time is equal to or less than the upper limit, the manufacturing time can be reduced, and the production cost tends to be reduced. When the pressurizing time is equal to or more than the lower limit, the void content in the bonding sheet 1 can be reduced, and the heat transfer performance and the withstand voltage characteristics tend to be improved.

[0072] After the second pressurization, the thermosetting sheet may be cured by heating or pressurization. In this case, the heating temperature is preferably 30 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. The pressure is preferably 4 MPa or higher, more preferably 5 MPa or higher, and even more preferably 6 MPa or higher. In addition, the pressure is preferably 150 MPa or lower, more preferably 100 MPa or lower, and even more preferably 20 MPa or lower.

[0073] For the above-mentioned pressurization method, various known press machines 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 machine that can reduce the amount of oxygen inside the press machine during heating, or a press machine equipped with a nitrogen substitution device. The heating method may include a method of adjusting the temperatures of the upper and lower top plates of the press device.

[0074] The thermosetting sheet may be subjected to aging. Aging may be performed, for example, by placing the thermosetting sheet in an environment preferably at a temperature of -50°C or higher but 0°C or lower, more preferably at a temperature of -30°C or higher or -5°C or lower, for a period of preferably 5 minutes to 365 days, more preferably 1 hour to 7 days. Aging can be performed after application, after heat drying, or after pressure application. Of these, after pressure application is preferred. Note that this pressure application differs from the heat pressing used to prepare the bonded body of the present invention, and refers to the pressure applied prior to the heat pressing used to prepare the thermosetting sheet.

[0075] <Explanation of terms, etc.> In the present invention, the term "film" includes the term "sheet", and the term "sheet" includes the term "film". In the present invention, when it is written "α to β" (α and β are arbitrary numbers), unless otherwise specified, it means "not less than α and not more than β", and also means "preferably greater than α" or "preferably smaller than β". Furthermore, when it is stated that "α or more" or "α≦" (α is any number), it also means "preferably greater than α" unless otherwise specified, and when it is stated that "β or less" or "≦β" (β is any number), it also means "preferably smaller than β" unless otherwise specified. [Example]

[0076] 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.

[0077] (Upper member 2a) The upper member 2a was prepared as a member measuring 21 mm long, 16 mm wide, and 5 mm thick. The upper member 2a was a copper plate measuring 16 mm long, 13 mm wide, and 2 mm thick, which had a Sn plating layer 2A made of tin on the entire lower surface of the metal member 2B, and the surrounding area except for the Sn plating layer 2A was covered with epoxy resin as resin 23. The area A of the Sn plating layer 2A was 16 mm long x 13 mm wide = 208 mm 2 It was.

[0078] (Lower member 3a) The lower member 3a was prepared by providing a 5 μm thick Ni-plated layer 3A made of nickel on the entire upper surface of a copper plate measuring 40 mm in length, 80 mm in width, and 2 mm in thickness as the metal member 3B. The area B of the Ni-plated layer 3A was 3200 mm 2 The type of plating used was electroless Ni plating, and it was a medium phosphorus type.

[0079] (Preparation of thermosetting resin sheet 1a) High molecular weight epoxy resin (mass average molecular weight in polystyrene equivalent: 30,000, epoxy equivalent: 9,000 g / equivalent) 9 parts by mass, multifunctional epoxy resin: multifunctional epoxy resin (molecular weight 500 or less) containing a structure having four or more glycidyl groups per molecule 7 parts by mass, biphenyl type solid epoxy resin (molecular weight approximately 400) 15 parts by mass, spherical boron nitride agglomerated particles with a house-of-card structure (average particle size (D50) 45 μm, maximum particle size (Dmax) 90 μm) 63 parts by mass, phenolic resin-based curing agent 5 parts by mass, curing catalyst (2,4-diamine A thermosetting resin composition in slurry form was prepared by mixing 0.4 parts by mass of 2-phenyl-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), together with equal amounts of methyl ethyl ketone and cyclohexanone, to a solids concentration of 74% by mass using a planetary centrifugal stirrer.

[0080] The average particle size (D50) and maximum particle size (Dmax) of the boron nitride agglomerated particles are determined by dispersing a thermally conductive filler 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 calculating the maximum particle size Dmax and the particle size at 50% of the cumulative volume (average particle size D50) from the obtained particle size distribution.

[0081] The thus obtained thermosetting resin composition in a slurry state was applied to a PET substrate by a doctor blade method, and the applied composition was dried by heating at 60°C for 120 minutes. Then, the applied composition was pressurized at 42°C and 1500 kgf / cm using a press. 2 The sheet was pressed at 100° C. for 10 minutes to obtain a sheet-shaped resin composition (referred to as "thermosetting resin sheet 1a") having a length of 20 mm, a width of 15 mm and a thickness of 150 μm. The total content of methyl ethyl ketone and cyclohexanone in the thermosetting resin sheet 1a was 1% by mass or less. The thermosetting resin sheet 1a was placed in a freezer at −20° C. for 2 days to perform low-temperature aging.

[0082] Example 1 Using the above-described upper member 2a, lower member 3a and thermosetting resin sheet 1a, a bonded body was produced as follows.

[0083] A thermosetting resin sheet 1a was directly laminated on the lower member 3a so as to contact the Ni-plated surface 3A, and a PET film with a release agent applied to the contact surface was further laminated on top of the thermosetting resin sheet 1a to form a laminate. This laminate was then set in a pressure press and hot-pressed at 80°C and a pressure of 6 MPa for 5 minutes. Next, the PET film was peeled off, and the upper member 2a was directly laminated on the thermosetting resin sheet 1a so that the Sn-plated layer 2A of the upper member 2a was in contact with the thermosetting resin sheet 1a to form a laminate. This laminate was then heat-pressed at 180°C and a pressure of 10 MPa for 30 minutes to harden the thermosetting resin sheet, thereby obtaining a bonded body in which the upper member 2a and the lower member 3a were bonded to the front and back of the 150 μm-thick bonding sheet 1.

[0084] <Methods for measuring physical properties, evaluation methods, and measurement results> The physical properties of the bonded structures produced in the examples and the bonded sheets 1 constituting the bonded structures were evaluated as follows.

[0085] (coefficient of linear expansion) In accordance with Example 1 above, the thermosetting resin sheet 1a was heat-pressed at 80°C under a pressure of 6 MPa for 5 minutes, and then heat-pressed at 180°C under a pressure of 10 MPa for 30 minutes to produce a hardened sheet similar to the bonding sheet 1 of Example 1.

[0086] The average linear expansion coefficient in the temperature range of 25° C. or higher and 200° C. or lower was measured as follows. The dimensional change of the above sheet when heated from -50°C to 230°C was measured under the following conditions using a thermomechanical analyzer TMA7100 (manufactured by Hitachi High-Tech Science Corporation). From the measurement results, the average value of the dimensional change rate at 25°C to 200°C in the third step was taken as the average linear expansion coefficient of the bonding sheet 1. The average linear expansion coefficient of the bonding sheet 1 at 25°C to 200°C was 45 ppm / K. The average linear expansion coefficient of copper at a temperature range of 25°C to 200°C was 17 ppm / K. Therefore, (average linear expansion coefficient of the bonding sheet 1 in ppm / K - average linear expansion coefficient of copper in ppm / K at a temperature range of 25°C to 200°C) was 28 ppm / K.

[0087] <Measurement conditions> Measurement mode: Tensile mode Atmosphere: 200 mL / min nitrogen flow Heating rate: 5°C / min Measurement temperature: 1st step: -50~230℃ 2nd step: 230 to -50°C 3rd step: -50 to 230℃ The average linear expansion coefficient at 25°C to 200°C was measured in the third step.

[0088] (elastic modulus) The elastic modulus (GPa) of the prepared sheet at 25° C. and 200° C. was measured in the same manner as in the measurement of the linear expansion coefficient. The dynamic viscoelasticity of the sheet was measured under the following conditions using a viscoelasticity spectrometer DVA-200 (manufactured by IT Measurement Control Co., Ltd.) From the measurement results, the storage modulus values ​​at 25°C and 200°C were read and defined as the storage modulus of the bonding sheet 1 at 25°C and 200°C. The storage modulus of bonding sheet 1 at 25° C. was 14 GPa, and the storage modulus of bonding sheet 1 at 200° C. was 4 GPa. Therefore, (elastic modulus of bonding sheet 1 at 25° C. GPa−elastic modulus of bonding sheet 1 at 200° C. GPa) was 10 GPa.

[0089] <Measurement conditions> Vibration frequency: 10Hz Distortion: 0.1% Heating rate: 2°C / min Measurement temperature: -100℃~220℃

[0090] (Water droplet contact angle) In the same manner as in the measurement of the linear expansion coefficient, the water droplet contact angle (°) of the prepared sheet was measured as follows. The contact angle of the sheet surface, which had been conditioned for 24 hours or more in an environment of 23°C and 50% RH, was measured using a dynamic contact angle measuring device FTA125 manufactured by First Ten Angstroms, and the water droplet contact angle was measured at five points on each side 30 seconds after a water droplet ejected from a 1 mm diameter needle came into contact with the surface of the sheet, and the average value was taken as the water droplet contact angle of the bonded sheet 1. The water droplet contact angle of the bonding sheet 1 was 85°.

[0091] (shear strength) The shear strength of the bonded bodies produced in the examples was measured before and after the following heat cycle test. The shear strength of the bonded structure was measured in accordance with JIS K 6254. As shown in Figure 4, the bonded structure produced in the example was stood upright with bonding sheet 1 vertical, and lower metal 3 was fixed. A downward force was applied to upper metal 2 using a jig. The strength of the force when upper metal 2 peeled off from the bonded structure was measured, and the value was divided by the area of ​​the adhesive surface between upper member 2 and bonding sheet 1 to calculate the shear strength (MPa). The area of ​​the adhesive surface between upper member 2 and bonding sheet 1 was 3.255 cm. 2 and the test speed is 100 mm / min. In addition, a thermal cycle test was performed on the bonded structures prepared in the examples using an ESPEC thermal shock tester TSA-41L-A. Each cycle consisted of 30 minutes of high-temperature exposure at 150°C, 1 minute of room-temperature exposure, and 30 minutes of low-temperature exposure at -40°C. Up to 1,000 cycles were performed. The shear strength of the bonded structure before the thermal cycle test was 9.1 MPa, and the shear strength of the bonded structure after the thermal cycle test was 4.1 MPa. Therefore, the (shear strength of the bonded structure before the thermal cycle test (MPa) / shear strength of the bonded structure after the thermal cycle test (MPa)) ratio was 2.2. This confirmed that the deterioration of adhesion due to temperature changes, particularly the deterioration of adhesion between the upper member 2 having the Sn-plated layer 2A and the bonding sheet 1, could be suppressed, and long-term reliability (TCT) could be maintained.

[0092] (Breakdown voltage (BDV) measurement) The bonded body obtained in the example 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 member 2B of the upper member 2 and the metal member 3B of the lower member 3. Using an ultra-high voltage withstand voltage tester 7470 (manufactured by Keisoku Giken), a voltage of 0.5 kV was applied to the bonded sheet 1 as shown in Figure 5, and the voltage was increased by 0.5 kV every 60 seconds.The voltage when a current of 1 mA or more was applied was measured and taken as the dielectric breakdown voltage (BDV). The breakdown voltage (BDV) of the bonding sheet 1 was more than 5 kV, which confirmed that the deterioration of the insulating properties was suppressed and that the bonding sheet 1 had excellent insulating properties.

[0093] (Measurement of thermal conductivity) A sheet was produced under the same conditions as the bonding sheet 1 in the bonded structure produced in Example 1. That is, a thermosetting resin sheet 1a was heat-pressed at 80°C under a pressure of 6 MPa for 5 minutes, and then heat-pressed at 180°C under a pressure of 10 MPa for 30 minutes to produce a cured sheet (measurement sample) similar to the bonding sheet 1 in Example 1. Two, three, or four thermosetting resin sheets 1a were stacked and heat-pressed in the same manner as above to produce four types of sheets (measurement samples) with different thicknesses. The thickness, area, and thermal resistance of each measurement sample were measured, and the thermal conductivity (25°C) in the sheet thickness direction in a steady state method was calculated from the slope represented by the thermal resistance value relative to the sheet thickness, and this was used as the thermal conductivity of the bonding sheet 1 (in accordance with ASTM D5470). The thermal resistance was measured using a Mentor Graphics T3ster DynTIM Tester, with a probe size of φ12.8 mm, a fixed pressure of 3400 kPa, and a measurement time of 300 seconds. Shin-Etsu Chemical's Oil Compound (product name: G-747) was used to improve adhesion between the sample and the probe. The thermal conductivity of bonding sheet 1 was 15 W / m·K.

[0094] (Composite physical properties) From the above measurement results, (shear strength of the bonded body before the thermal cycle test (MPa) / shear strength of the bonded body after the thermal cycle test (MPa)) × (elastic modulus of the bonding sheet 1 at 25°C (GPa)−elastic modulus of the bonding sheet 1 at 200°C (GPa)) × (average linear expansion coefficient of the bonding sheet 1 in the temperature range of 25°C to 200°C (ppm / K)−average linear expansion coefficient of copper (ppm / K)) × (water droplet contact angle of the bonding sheet 1 (°)) ÷ (thickness of the bonding sheet 1 (μm)) was 352 (GPa × °) / (m × K). The average linear expansion coefficient of copper in the temperature range of 25°C or higher and 200°C or lower was 17 ppm / K.

[0095] (Consideration) From the above examples and the test results that the inventors have conducted so far, it has been found that for a joint structure in which an upper member 2 having a Sn-plated layer 2A on its joining surface and a lower member 3 having a Ni-plated layer 3A on its joining surface are joined to the front and back of a joining sheet 1, by making the area A of the Sn-plated layer 2A, which has a large linear expansion coefficient, smaller than the area B of the Ni-plated layer 3A, which has a small linear expansion coefficient, it is possible to suppress a decrease in adhesion due to temperature changes, particularly a decrease in adhesion between the upper member 2 having the Sn-plated layer 2A and the joining sheet 1, and it is also possible to suppress a decrease in insulation, thereby maintaining long-term reliability (TCT). [Explanation of symbols]

[0096] 1 Bonding sheet 2 Upper member 2A Sn plating layer 2B Metallic parts 21 Semiconductor chips 22 Wiring materials 23 Resin 3 Lower member 3A Ni plating layer 3B Metal parts

Claims

1. A joined body having a configuration in which an upper member 2 and a lower member 3 are directly joined to the front and back of a joining sheet 1, The upper member 2 has a Sn plating layer 2A mainly made of tin or a tin alloy on its lower surface, i.e., the joining surface, and the lower member 3 has a Ni plating layer 3A mainly made of nickel or a nickel alloy on its upper surface, i.e., the joining surface. The bonding sheet 1 is a cured product of a thermosetting resin composition containing a thermosetting resin and an inorganic filler, A joined body in which the area A of the Sn-plated layer 2A of the upper member 2 and the area B of the Ni-plated layer 3A of the lower member 3 satisfy the relationship area A < area B.

2. (Shear strength MPa of the bonded body before the following heat cycle test / Shear strength MPa of the bonded body after the following heat cycle test) × (elastic modulus of the bonded sheet 1 at 25 ° C. GPa - elastic modulus of the bonded sheet 1 at 200 ° C. GPa) × (average linear expansion coefficient of the bonded sheet 1 in a temperature range of 25 ° C. to 200 ° C. ppm / K - average linear expansion coefficient of copper ppm / K) × (water droplet contact angle of the bonded sheet 1 °) ÷ (thickness μm of the bonded sheet 1) is 0.15 or more and 7500 or less ((GPa × °) / (m × K))). The bonded body according to claim 1. Thermal cycle test: The bonded body is subjected to 1000 cycles, with one cycle consisting of 30 minutes at -40°C, 1 minute at 25°C, and 30 minutes at 150°C. Shear strength: The shear strength (MPa) of the bonded body is measured in accordance with JIS K 6254.

3. 3. The bonded body according to claim 1, wherein the bonding sheet has an average linear expansion coefficient of 20 ppm / K or more and 80 ppm / K or less in a temperature range of 25°C or more and 200°C or less.

4. 3. The joined body according to claim 1, wherein the ratio (B / A) of the area B of the Ni-plated layer 3A of the lower member 3 to the area A of the Sn-plated layer 2A of the upper member 2 is 1.5 or more and 500 or less.

5. The bonded body according to claim 1 or 2, wherein the inorganic filler contained in the bonding sheet (1) comprises agglomerated particles of boron nitride.

6. The bonded structure according to claim 1 or 2, wherein the thermosetting resin contained in the bonding sheet (1) includes an epoxy resin.

7. The bonded structure according to claim 1 or 2, wherein the thickness of the bonding sheet is 80 μm or more and 300 μm or less.

8. The upper member 2 is a metal member 2B mainly made of copper, and has a Sn-plated layer 2A on the lower surface thereof.

3. The joined body according to claim 1, wherein the lower member (3) is a metal member (3B) mainly made of copper, and the upper surface of the metal member (3B) is provided with a Ni-plated layer (3A).

9. The area A of the Sn plating layer 2A of the upper member 2 is 0.25 cm ２ More than 50cm ２ The area B of the Ni plating layer 3A of the lower member 3 is 0.4 cm ２ More than 600cm ２ 3. The conjugate according to claim 1 or 2, wherein:

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