Copper / ceramic bonded body, insulated circuit board, and method for manufacturing copper / ceramic bonded body and insulated circuit board

Abstract

To provide: a copper / ceramic assembly which is capable of suppressing the generation of cracks of a ceramic member even if a severe cold heat cycle is loaded, and also which is excellent in migration resistance; an insulated circuit board; a method for producing a copper / ceramic assembly; and a method for producing an insulated circuit board.SOLUTION: There is provided a copper / ceramic assembly in which a copper member 12 comprising copper or a copper alloy is bonded to a ceramic member 11 comprising a nitrogen-containing ceramic. A Mg solid solution layer in which Mg is solid-solved in a Cu matrix phase is formed at a bonding interface between the copper member 12 and the ceramic member 11, and an active metal nitride layer 41 containing nitrides of one or two or more active metals selected from among Ti, Zr, Nb and Hf is formed on the ceramic member 11 side of the bonding interface. The thickness of the active metal nitride layer 41 is within the range of 0.05 μm or more and 1.2 μm or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a copper / ceramic bonded body formed by bonding a copper member made of copper or a copper alloy to a ceramic member, an insulated circuit board formed by bonding a copper plate made of copper or a copper alloy to the surface of a ceramic substrate, a method for manufacturing a copper / ceramic bonded body, and a method for manufacturing an insulated circuit board. [Background technology]

[0002] In power modules, LED modules, and thermoelectric modules, a power semiconductor element, an LED element, and a thermoelectric element are bonded to an insulating circuit board having a circuit layer made of a conductive material formed on one side of an insulating layer. For example, power semiconductor elements for controlling large amounts of power, which are used to control wind power generation, electric vehicles, hybrid vehicles, etc., generate a large amount of heat during operation, and therefore, as a substrate for mounting these elements, an insulated circuit board has been widely used, which includes a ceramic substrate and a circuit layer formed by bonding a metal plate with excellent conductivity to one surface of the ceramic substrate. Note that an insulated circuit board in which a metal layer is formed by bonding a metal plate to the other surface of the ceramic substrate is also provided.

[0003] For example, Patent Document 1 proposes an insulated circuit board in which a circuit layer and a metal layer are formed by bonding copper plates to one side and the other side of a ceramic substrate. In Patent Document 1, copper plates are placed on one side and the other side of the ceramic substrate with an Ag-Cu-Ti based brazing material interposed therebetween, and the copper plates are bonded by heat treatment (a so-called active metal brazing method). This active metal brazing method uses a brazing material containing Ti, which is an active metal, and therefore improves the wettability between the molten brazing material and the ceramic substrate, resulting in good bonding between the ceramic substrate and the copper plate.

[0004] Furthermore, Patent Document 2 proposes an insulating circuit board in which a ceramic substrate and a copper plate are joined together using a Cu-Mg-Ti brazing filler metal. In Patent Document 2, the joining is performed by heating at 560 to 800°C in a nitrogen gas atmosphere, and the Mg in the Cu-Mg-Ti alloy sublimes and does not remain at the joining interface, and titanium nitride (TiN) is not substantially formed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3211856 [Patent Document 2] Patent No. 4375730 Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, high-temperature semiconductor devices using SiC or the like are sometimes mounted at high density, and the insulating circuit board must be able to guarantee operation at higher temperatures. Therefore, it is necessary to suppress the occurrence of cracks in the ceramic substrate even when it is subjected to more severe thermal cycles than before.

[0007] Furthermore, as disclosed in Patent Document 1, when a ceramic substrate and a copper plate are joined by active metal brazing, Ag is present at the joining interface, which makes it prone to migration when used under high-temperature and high-humidity conditions, making it unsuitable for high-voltage applications.

[0008] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a copper / ceramic bonded body, an insulated circuit board, and a method for manufacturing a copper / ceramic bonded body and an insulated circuit board, which are capable of suppressing the occurrence of cracks in ceramic members even when subjected to severe thermal cycles and have excellent migration resistance. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, a copper / ceramic joined body of the present invention is a copper / ceramic joined body obtained by joining a copper member made of copper or a copper alloy to a ceramic member made of a nitrogen-containing ceramic, wherein a Mg solid solution layer in which Mg is solid-solved in a Cu matrix is ​​formed at the joining interface between the copper member and the ceramic member, and an active metal nitride layer containing nitrides of one or more active metals selected from Ti, Zr, Nb and Hf is formed on the ceramic member side, and the thickness of this active metal nitride layer is in the range of 0.05 μm to 1.2 μm. and there is no region between the Mg solid solution layer and the ceramic member where the active metal nitride layer is not present. It is characterized by the following.

[0010] In the copper / ceramic joined body of the present invention, an active metal nitride layer containing nitrides of one or more active metals selected from Ti, Zr, Nb, and Hf is formed on the ceramic member side of the joining interface between the copper member and the ceramic member, and the thickness of this active metal nitride layer is 0.05 μm or more, so that a uniform interfacial reaction progresses during joining, and cracking of the ceramic member can be suppressed when subjected to thermal cycling. Furthermore, the thickness of this active metal nitride layer is 1.2 μm or less, so that cracking of the ceramic member can be suppressed when subjected to thermal cycling. Furthermore, since there is no Ag at the bonding interface, it also has excellent migration resistance.

[0011] In the copper / ceramic bonded body of the present invention, the active metal is preferably Ti. In this case, Ti reacts sufficiently with the joining surface of the ceramic member to form an active metal nitride layer made of titanium nitride, making it possible to reliably join the ceramic member and the copper member.

[0012] In the copper / ceramic bonded body of the present invention, it is preferable that Cu-containing particles are present inside the active metal nitride layer. In this case, the strength of the active metal nitride layer formed at the bonding interface is improved, and peeling between the ceramic member and the copper member can be suppressed when ultrasonic waves are applied to ultrasonically bond, for example, a terminal material to a copper member.

[0013] The insulated circuit board of the present invention is an insulated circuit board in which a copper plate made of copper or a copper alloy is bonded to the surface of a ceramic substrate made of nitrogen-containing ceramic, and at the bonding interface between the copper plate and the ceramic substrate, an Mg solid solution layer in which Mg is solid-solved in a Cu matrix is ​​formed, and an active metal nitride layer containing nitrides of one or more active metals selected from Ti, Zr, Nb, and Hf is formed on the ceramic substrate side, and the thickness of this active metal nitride layer is within the range of 0.05 μm to 1.2 μm. and there is no region between the Mg solid solution layer and the ceramic substrate where the active metal nitride layer is not present. It is characterized by the following.

[0014] According to the insulating circuit board of the present invention, an active metal nitride layer containing nitrides of one or more active metals selected from Ti, Zr, Nb, and Hf is formed on the ceramic substrate side of the bonding interface between the copper plate and the ceramic substrate, and the thickness of this active metal nitride layer is 0.05 μm or more, which allows a uniform interfacial reaction to proceed during bonding and suppresses cracking of the ceramic member when subjected to thermal cycles.Furthermore, the thickness of this active metal nitride layer is 1.2 μm or less, which suppresses cracking of the ceramic substrate when subjected to thermal cycles. Furthermore, since there is no Ag at the bonding interface, it also has excellent migration resistance.

[0015] In the insulating circuit board of the present invention, the active metal is preferably Ti. In this case, Ti reacts sufficiently with the joining surface of the ceramic substrate to form an active metal nitride layer made of titanium nitride, making it possible to reliably join the ceramic substrate and the copper plate.

[0016] In the insulating circuit board of the present invention, it is preferable that Cu-containing particles are present inside the active metal nitride layer. In this case, the strength of the active metal nitride layer formed at the bonding interface is improved, and peeling between the ceramic substrate and the copper plate can be suppressed when ultrasonic waves are applied to ultrasonically bond, for example, a terminal material to an insulating circuit board.

[0017] The method for producing a copper / ceramic bonded body of the present invention is a method for producing the above-mentioned copper / ceramic bonded body, and includes an active metal and Mg arranging step of arranging one or more active metals selected from Ti, Zr, Nb, and Hf and Mg between the copper member and the ceramic member; a laminating step of laminating the copper member and the ceramic member with the active metal and Mg interposed therebetween; and a joining step of joining the copper member and the ceramic member, which have been laminated with the active metal and Mg interposed therebetween, by heat treatment in a vacuum atmosphere while applying pressure to the copper member and the ceramic member, the laminated members being laminated with the active metal and Mg interposed therebetween, in a laminating direction. In the active metal and Mg arranging step, the amount of the active metal is set to 0.4 μmol / cm. 2 More than 18.8μmol / cm 2 Within the following range, Mg content is 14 μmol / cm 2 More than 86μmol / cm 2 The bonding step is characterized in that the heating rate in the temperature range of 450°C or higher and lower than 650°C is 5°C / min or higher and 20°C / min or lower, the holding temperature is in the range of 700°C or higher and 850°C or lower, and the holding time at the holding temperature is in the range of 10 min or higher and 180 min or lower.

[0018] According to the method for producing a copper / ceramic bonded body having this configuration, the amount of active metal is 0.4 μmol / cm 2 More than 18.8μmol / cm 2 Within the following range, Mg content is 14 μmol / cm 2 More than 86μmol / cm 2 By setting the temperature within the range below, it is possible to obtain a sufficient amount of liquid phase necessary for the interface reaction, thereby ensuring reliable bonding of the copper member and the ceramic member. Furthermore, as described above, in the bonding process with Mg and an active metal interposed therebetween, the heating rate is set to 5°C / min or more and 20°C / min or less in the temperature range of 450°C or more and less than 650°C, the holding temperature is set to 700°C or more and 850°C or less, and the holding time at the holding temperature is set to 10 minutes or more and 180 minutes or less. This allows an active metal nitride layer to be formed at the bonding interface, but prevents this active metal nitride layer from growing to an unnecessarily thick thickness. As a result, the thickness of the active metal nitride layer can be set to a range of 0.05 μm or more and 1.2 μm or less.

[0019] The method for producing an insulated circuit board of the present invention is a method for producing the above-mentioned insulated circuit board, and includes an active metal and Mg arranging step of arranging one or more active metals selected from Ti, Zr, Nb, and Hf and Mg between the copper plate and the ceramic substrate; a laminating step of laminating the copper plate and the ceramic substrate with the active metal and Mg interposed therebetween; and a bonding step of bonding the copper plate and the ceramic substrate, which have been laminated with the active metal and Mg interposed therebetween, by heat treatment in a vacuum atmosphere while applying pressure in the laminating direction, wherein in the active metal and Mg arranging step, the amount of active metal is 0.4 μmol / cm 2 More than 18.8μmol / cm 2 Within the following range, Mg content is 14 μmol / cm 2 More than 86μmol / cm 2 The bonding step is characterized in that the heating rate in the temperature range of 450°C or higher and lower than 650°C is 5°C / min or higher and 20°C / min or lower, the holding temperature is in the range of 700°C or higher and 850°C or lower, and the holding time at the holding temperature is in the range of 10 min or higher and 180 min or lower.

[0020] According to the method for producing an insulating circuit board having this configuration, the amount of active metal is 0.4 μmol / cm 2 More than 18.8μmol / cm 2 Within the following range, Mg content is 14 μmol / cm 2 More than 86μmol / cm 2By setting the temperature within the range below, it is possible to obtain a sufficient amount of liquid phase necessary for the interface reaction, thereby ensuring reliable bonding between the copper plate and the ceramic substrate. Furthermore, as described above, in the bonding process with Mg and an active metal interposed therebetween, the heating rate is set to 5°C / min or more and 20°C / min or less in the temperature range of 450°C or more and less than 650°C, the holding temperature is set to 700°C or more and 850°C or less, and the holding time at the holding temperature is set to 10 minutes or more and 180 minutes or less. This allows an active metal nitride layer to be formed at the bonding interface, but prevents this active metal nitride layer from growing to an unnecessarily thick thickness. As a result, the thickness of the active metal nitride layer can be set to a range of 0.05 μm or more and 1.2 μm or less. [Effects of the Invention]

[0021] According to the present invention, it is possible to provide a copper / ceramic bonded body, an insulated circuit board, a method for manufacturing a copper / ceramic bonded body, and an insulated circuit board that can suppress the occurrence of cracks in ceramic members even when subjected to severe thermal cycles and have excellent migration resistance. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a schematic explanatory diagram of a power module using an insulating circuit board according to an embodiment of the present invention. FIG. [Figure 2] 2 is an enlarged explanatory view of a bonding interface between a circuit layer (metal layer) and a ceramic substrate of the insulating circuit board according to the embodiment of the present invention. FIG. [Figure 3] 1 is a flowchart of a method for manufacturing an insulating circuit board according to an embodiment of the present invention. [Figure 4] 1A to 1C are schematic explanatory views of a method for manufacturing an insulating circuit board according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The bonded body according to this embodiment is an insulating circuit board 10 formed by bonding a ceramic substrate 11 as a ceramic member made of ceramic to a copper plate 22 (circuit layer 12) and a copper plate 23 (metal layer 13) as copper members made of copper or a copper alloy. Fig. 1 shows a power module 1 including the insulating circuit board 10 according to this embodiment.

[0024] This power module 1 includes an insulating circuit board 10 having a circuit layer 12 and a metal layer 13 arranged thereon, a semiconductor element 3 bonded to one surface (the upper surface in FIG. 1) of the circuit layer 12 via a bonding layer 2, and a heat sink 30 arranged on the other side (the lower side in FIG. 1) of the metal layer 13.

[0025] The semiconductor element 3 is made of a semiconductor material such as Si, etc. The semiconductor element 3 and the circuit layer 12 are bonded together via a bonding layer 2. The bonding layer 2 is made of, for example, an Sn--Ag based, Sn--In based, or Sn--Ag--Cu based solder material.

[0026] The heat sink 30 is used to dissipate heat from the insulating circuit board 10. The heat sink 30 is made of copper or a copper alloy, and in this embodiment, is made of phosphorus-deoxidized copper. The heat sink 30 is provided with a flow path 31 through which a cooling fluid flows. In this embodiment, the heat sink 30 and the metal layer 13 are joined together by a solder layer 32 made of a solder material. The solder layer 32 is made of, for example, a Sn—Ag-based, Sn—In-based, or Sn—Ag—Cu-based solder material.

[0027] As shown in FIG. 1, the insulating circuit board 10 of this embodiment comprises a ceramic substrate 11, a circuit layer 12 disposed on one surface (the upper surface in FIG. 1) of the ceramic substrate 11, and a metal layer 13 disposed on the other surface (the lower surface in FIG. 1) of the ceramic substrate 11.

[0028] The ceramic substrate 11 is made of nitrogen-containing ceramics with excellent insulating and heat dissipating properties, and in this embodiment is made of aluminum nitride (AlN). The thickness of this ceramic substrate 11 is set, for example, within the range of 0.2 mm to 1.5 mm, and in this embodiment is set to 0.635 mm. In addition to aluminum nitride (AlN), silicon nitride (Si3N4) can also be used.

[0029] As shown in FIG. 4, the circuit layer 12 is formed by bonding a copper plate 22 made of copper or a copper alloy to one surface (the upper surface in FIG. 4) of the ceramic substrate 11. In this embodiment, the circuit layer 12 is formed by bonding a copper plate 22 made of a rolled sheet of oxygen-free copper to the ceramic substrate 11. The thickness of the copper plate 22 that becomes the circuit layer 12 is set within the range of 0.1 mm to 2.0 mm, and in this embodiment, it is set to 0.6 mm.

[0030] As shown in FIG. 4, the metal layer 13 is formed by joining a copper plate 23 made of copper or a copper alloy to the other surface (the lower surface in FIG. 4) of the ceramic substrate 11. In this embodiment, the metal layer 13 is formed by bonding a copper plate 23 made of a rolled sheet of oxygen-free copper to the ceramic substrate 11. The thickness of the copper plate 23 that will become the metal layer 13 is set within the range of 0.1 mm to 2.0 mm, and in this embodiment, it is set to 0.6 mm.

[0031] At the bonding interface between the ceramic substrate 11 and the circuit layer 12 (metal layer 13), as shown in FIG. 2, an active metal nitride layer 41 containing nitrides of one or more active metals selected from Ti, Zr, Nb, and Hf is formed on the ceramic substrate 11 side. The thickness of this active metal nitride layer 41 is set to be in the range of 0.05 μm to 1.2 μm. In this embodiment, it is preferable to use Ti as the active metal. The thickness of the active metal nitride layer 41 may be set to be in the range of 0.15 μm to 1.0 μm. As shown in FIG. 2, an Mg solid solution layer 42 in which Mg is dissolved in Cu is formed on the side of the active metal nitride layer 41 facing the circuit layer 12 (metal layer 13). Furthermore, in this embodiment, it is preferable that one or more types of Cu-containing particles selected from Cu particles, compound particles of Cu and an active metal, and compound particles of Cu and Mg are present inside the active metal nitride layer 41. The Cu-containing particles may be present in a dispersed state inside the active metal nitride layer 41.

[0032] A method for manufacturing the insulating circuit board 10 according to this embodiment will be described below with reference to FIGS.

[0033] (Active metal and Mg placement step S01) First, a ceramic substrate 11 made of aluminum nitride (AlN) is prepared, and as shown in FIG. 4, one or more active metals selected from Ti, Zr, Nb, and Hf and Mg are placed between the ceramic substrate 11 and a copper plate 22 that will become the circuit layer 12, and between the ceramic substrate 11 and a copper plate 23 that will become the metal layer 13, respectively. In this embodiment, an Mg foil 25 and an active metal foil 26 are disposed between the copper plate 22 that will become the circuit layer 12 and the ceramic substrate 11, and between the copper plate 23 that will become the metal layer 13 and the ceramic substrate 11.

[0034] Here, in the active metal and Mg arranging step S01, the amount of the arranged active metal is 0.4 μmol / cm 2 More than 18.8μmol / cm 2 Within the following range, Mg content is 14 μmol / cm 2 More than 86μmol / cm 2 Within the following range. The lower limit of the amount of active metal to be placed is 0.9 μmol / cm 2It is preferable that the concentration is 2.8 μmol / cm or more. 2 On the other hand, the upper limit of the amount of active metal to be placed is 9.4 μmol / cm 2 It is preferable that the concentration is 6.6 μmol / cm or less. 2 It is more preferable that: The lower limit of the amount of Mg to be placed is 21 μmol / cm 2 It is preferable that the concentration is 28 μmol / cm or more. 2 On the other hand, the upper limit of the amount of Mg to be placed is 72 μmol / cm 2 It is preferable that the concentration is 57 μmol / cm or less. 2 It is more preferable that:

[0035] (Lamination process S02) Next, the copper plate 22 and the ceramic substrate 11 are laminated together with the active metal foil 26 and the Mg foil 25 interposed therebetween, and the ceramic substrate 11 and the copper plate 23 are laminated together with the active metal foil 26 and the Mg foil 25 interposed therebetween.

[0036] (Joining process S03) Next, the stacked copper plate 22, active metal foil 26, Mg foil 25, ceramic substrate 11, Mg foil 25, active metal foil 26, and copper plate 23 are pressed in the stacking direction and placed in a vacuum furnace for heating, thereby bonding the copper plate 22, ceramic substrate 11, and copper plate 23 together. Here, the heat treatment conditions in the bonding step S03 are a temperature rise rate of 5°C / min or more and 20°C / min or less in the temperature range of 450°C or more and less than 650°C, a holding temperature in the range of 700°C or more and 850°C or less, and a holding time at the holding temperature in the range of 10 min or more and 180 min or less.

[0037] The lower limit of the heating rate in the temperature range of 450° C. or higher and lower than 650° C. is preferably 7° C. / min or higher, and more preferably 9° C. / min or higher. On the other hand, the upper limit of the heating rate in the temperature range of 450° C. or higher and lower than 650° C. is preferably 15° C. / min or lower, and more preferably 20° C. / min or lower. The lower limit of the holding temperature is preferably 730° C. or higher, and more preferably 760° C. or higher. On the other hand, the upper limit of the holding temperature is preferably 850° C. or lower, and more preferably 830° C. or lower. Furthermore, the lower limit of the retention time is preferably 30 minutes or more, more preferably 45 minutes or more, while the upper limit of the retention time is preferably 150 minutes or less, more preferably 120 minutes or less.

[0038] The pressure load in the joining step S03 is preferably set within a range of 0.049 MPa or more and 3.4 MPa or less. Furthermore, the degree of vacuum in the bonding step S03 is 1×10 -6 Pa or more 5×10 -2 It is preferable to set it in the range of Pa or less.

[0039] As described above, by the active metal and Mg arrangement step S01, the stacking step S02, and the bonding step S03, the thickness of the active metal nitride layer 41 formed at the bonding interface between the circuit layer 12 (metal layer 13) and the ceramic substrate 11 is within the range of 0.05 μm or more and 1.2 μm or less, and the insulating circuit board 10 of this embodiment is manufactured.

[0040] (Heat sink bonding process S04) Next, the heat sink 30 is bonded to the other surface of the metal layer 13 of the insulating circuit board 10 . The insulating circuit board 10 and the heat sink 30 are stacked with a solder material interposed therebetween and placed in a heating furnace, where the insulating circuit board 10 and the heat sink 30 are solder-joined via the solder layer 32 .

[0041] (Semiconductor element bonding process S05) Next, the semiconductor element 3 is joined to one surface of the circuit layer 12 of the insulating circuit board 10 by soldering. Through the above steps, the power module 1 shown in FIG. 1 is manufactured.

[0042] In the insulating circuit board 10 (copper / ceramic bonded body) of this embodiment configured as described above, an active metal nitride layer 41 containing nitrides of one or more active metals selected from Ti, Zr, Nb, and Hf is formed on the ceramic substrate 11 side of the bonding interface between the circuit layer 12 and the metal layer 13 and the ceramic substrate 11. Because the thickness of this active metal nitride layer 41 is 0.05 μm or greater, a uniform interfacial reaction occurs during bonding, thereby suppressing cracking of the ceramic substrate 11 during thermal cycling. Specifically, if the thickness of the active metal nitride layer 41 is less than 0.05 μm, the interfacial reaction may be insufficient, resulting in regions lacking the active metal nitride layer 41. These regions may serve as initiation points for localized fracture of the ceramic substrate 11, resulting in cracking of the ceramic substrate 11 during thermal cycling. Furthermore, because the thickness of this active metal nitride layer 41 is 1.2 μm or less, cracking of the ceramic substrate 11 during thermal cycling may be suppressed. Furthermore, since there is no Ag at the bonding interface, it has excellent migration resistance and can ensure pressure resistance even when used under high temperature and high humidity conditions.

[0043] Furthermore, in this embodiment, when the active metal is Ti, Ti reacts sufficiently with the ceramic substrate 11 to form an active metal nitride layer 41 made of titanium nitride, thereby enabling reliable bonding between the ceramic substrate 11 and the circuit layer 12 (and the metal layer 13).

[0044] Furthermore, in this embodiment, the strength of the active metal nitride layer 41 formed at the bonding interface is improved when one or more types of Cu-containing particles selected from Cu particles, compound particles of Cu and an active metal, and compound particles of Cu and Mg are present inside the active metal nitride layer 41. Therefore, even when ultrasonic waves are applied to the insulating circuit board 10 (copper / ceramic bonded body) to ultrasonically bond a terminal material or the like to the circuit layer 12 (metal layer 13), peeling between the ceramic substrate 11 and the circuit layer 12 (metal layer 13) can be suppressed.

[0045] According to the method for producing an insulating circuit board of this embodiment, the amount of active metal is 0.4 μmol / cm 2 More than 18.8μmol / cm 2 Within the following range, Mg content is 14 μmol / cm 2 More than 86μmol / cm 2 The amount of active metal is within the range below, so that a sufficient amount of liquid phase necessary for the interface reaction can be obtained. Therefore, the circuit layer 12 and the metal layer 13 can be reliably bonded to the ceramic substrate 11. The amount of active metal is 18.8 μmol / cm 2 If the amount of active metal exceeds 0.4 μmol / cm, the interfacial reaction becomes excessive, and the active metal nitride layer grows excessively and becomes thick. 2 If the Mg content is less than 86 μmol / cm, the interfacial reaction is too small and the active metal nitride layer cannot grow sufficiently, resulting in a thin layer. 2 When the Mg content exceeds 14 μmol / cm, the amount of liquid phase becomes excessive, and the active metal nitride layer grows excessively and becomes thick. 2 If the temperature is less than this, the amount of liquid phase will be insufficient, and the active metal nitride layer will not grow sufficiently and will be thin.

[0046] In the bonding step S03, with Mg and an active metal interposed between them as described above, the heating rate is set to 5°C / min or more and 20°C / min or less in the temperature range of 450°C or more and less than 650°C, the holding temperature is set to 700°C or more and 850°C or less, and the holding time at the holding temperature is set to 10 minutes or more and 180 minutes or less. This allows the active metal nitride layer 41 to be formed at the bonding interface and prevents the active metal nitride layer 41 from growing to an excessively thick thickness. As a result, the thickness of the active metal nitride layer 41 can be set to a range of 0.05 μm or more and 1.2 μm or less. If the heating rate exceeds 20°C / min, the amount of Mg consumed by the diffusion of Mg into Cu and the growth of the Cu-Mg intermetallic compound phase is small, and the amount of liquid phase produced is excessive, resulting in the active metal nitride layer growing excessively thick. If the heating rate is less than 5°C / min, the amount of Mg consumed increases due to the diffusion of Mg into Cu and the growth of the Cu-Mg intermetallic compound phase, resulting in an insufficient amount of liquid phase produced and an insufficient active metal nitride layer, which results in a thin layer. Since the holding temperature is 850°C or less, the eutectic temperature of Cu and the active metal is not exceeded, thereby suppressing excessive growth of the active metal nitride layer, and since the holding temperature is 700°C or more, the temperature exceeds the melting point of Mg, thereby ensuring the progress of the interfacial reaction.Since the holding time is 180 minutes or less, the interfacial reaction does not proceed excessively, while since the holding time is 10 minutes or more, the interfacial reaction can be ensured to proceed.

[0047] Although the embodiment of the present invention has been described above, the present invention is not limited to this and can be modified as appropriate within the scope of the technical idea of ​​the invention. For example, in the present embodiment, a power module is described as being configured by mounting a semiconductor element on an insulating circuit board, but the present invention is not limited to this. For example, an LED module may be configured by mounting an LED element on a circuit layer of an insulating circuit board, or a thermoelectric module may be configured by mounting a thermoelectric element on a circuit layer of an insulating circuit board.

[0048] In addition, in the insulating circuit board of this embodiment, the circuit layer and the metal layer are both made of copper plates made of copper or a copper alloy, but this is not limiting. For example, as long as the circuit layer and the ceramic substrate are formed of the copper / ceramic bonded body of the present invention, there are no limitations on the material of the metal layer or the bonding method. The metal layer may be absent, may be formed of aluminum or an aluminum alloy, or may be formed of a laminate of copper and aluminum. On the other hand, as long as the metal layer and the ceramic substrate are formed of the copper / ceramic bonded body of the present invention, there are no limitations on the material and bonding method of the circuit layer, and the circuit layer may be formed of aluminum or an aluminum alloy, or may be formed of a laminate of copper and aluminum.

[0049] Furthermore, in this embodiment, an active metal foil and an Mg foil are laminated between a copper plate and a ceramic substrate. However, this is not limited to this, and an alloy foil of Mg and an active metal may also be disposed. Furthermore, a thin film made of Mg, an active metal, an alloy of Mg and an active metal, or the like may be formed on the bonding surfaces of the ceramic substrate and the copper plate by a sputtering method, a vapor deposition method, or the like. Furthermore, a paste using Mg or MgH2, a paste using an active metal or an active metal hydride, or a mixed paste of these may also be used. [Example]

[0050] The results of confirmation experiments conducted to confirm the effects of the present invention will be described below.

[0051] Example 1 First, a ceramic substrate (40 mm x 40 mm x 0.635 mm) made of aluminum nitride (AlN) and a ceramic substrate (40 mm x 40 mm x 0.32 mm) made of silicon nitride (Si3N4) were prepared. Copper plates (37 mm × 37 mm × 0.3 mm thick) made of oxygen-free copper were bonded to both sides of this ceramic substrate under the conditions shown in Tables 1 and 2 to obtain an insulated circuit board (copper / ceramic bonded body). The degree of vacuum in the vacuum furnace during bonding was 8 × 10 -3 It was Pa. Here, ceramic substrates made of aluminum nitride (AlN) were used in Inventive Examples 1 to 9, Comparative Examples 1 to 6, and Conventional Example 1. Furthermore, ceramic substrates made of silicon nitride (Si3N4) were used in Inventive Examples 11 to 19, Comparative Examples 11 to 16, and Conventional Example 11. Note that Conventional Examples 1 and 11 did not use Mg, but instead used Ag in the amounts shown in Tables 1 and 2.

[0052] The obtained insulating circuit board (copper / ceramic bonded body) was evaluated for the thickness of the active metal nitride layer at the bonded interface, the presence or absence of an Mg solid solution layer, migration resistance, and thermal cycle reliability as follows.

[0053] (Thickness of the active metal nitride layer) An observation sample was taken from the center of the cross section of the obtained insulating circuit board (copper / ceramic bonded body), and the bonding interface between the copper plate and the ceramic substrate was observed using a scanning transmission electron microscope (FEI Titan ChemiSTEM (with EDS detector)) at magnifications of 40,000 to 115,000 times and an acceleration voltage of 200 kV. Mapping was performed using energy dispersive X-ray analysis (Thermo Scientific NSS7), and an electron diffraction pattern was obtained by irradiating the region where the active metal and N overlap with an electron beam narrowed to about 1 nm (NBD (nanobeam diffraction) method), and the active metal nitride layer was confirmed. The thickness of the active metal nitride layer was measured using a scanning transmission electron microscope (FEI Titan ChemiSTEM (with EDS detector)) using the same sample as the above observation sample, obtaining elemental mapping of nitride-forming elements (Ti, Nb, Hf, Zr) and N, and regarding the region where nitride-forming elements and nitrogen (N) coexist as the active metal nitride layer, measuring the area of ​​this region and dividing it by the width of the measurement field of view. This measurement was performed at five points on the same sample, and the arithmetic mean of the obtained values ​​was taken as the thickness of the active metal nitride layer. The thickness of the region that was to become the active metal nitride layer was measured at five points per field of view, and the average value was taken as the thickness of the active metal nitride layer.

[0054] (Mg solid solution layer) An observation sample was taken from the center of the obtained insulating circuit board (copper / ceramic bonded body), and the bonding interface between the copper plate and the ceramic substrate was observed using an EPMA device (JXA-8539F manufactured by JEOL Ltd.) at a magnification of 2000x and an accelerating voltage of 15 kV in a region (400 μm × 600 μm) including the bonding interface. Quantitative analysis was performed at 10 points at 10 μm intervals from the surface of the ceramic substrate toward the copper plate, and the region with an Mg concentration of 0.01 atomic % or more was determined to be an Mg solid solution layer.

[0055] (migration resistant) After leaving the circuit layer for 500 hours under the conditions of a distance of 0.8 mm between circuit patterns, a temperature of 60°C, humidity of 95% RH, and a voltage of DC 50 V, the electrical resistance between the circuit patterns was measured and the resistance value was 1×10 6When the resistance was Ω or less, it was determined that a short circuit had occurred and was marked with "X". Otherwise, it was marked with "O".

[0056] (thermal cycle reliability) After passing the specimen through a furnace with a thermal cycle of -78°C for 2 minutes ←→ 350°C for 2 minutes, the bonding interface between the copper plate and the ceramic substrate was inspected using an SAT test to check for ceramic cracks and evaluate the number of cycles at which cracks were confirmed. In addition, in Examples 1 to 9 of the present invention and Comparative Examples 1 and 2, which used aluminum nitride (AlN) as the ceramic substrate, the above-mentioned thermal cycling was carried out up to 10 cycles, and those in which no cracks were observed after 10 cycles were indicated as ">10." In addition, in Examples 11 to 19 of the present invention and Comparative Examples 11 and 12, which used silicon nitride (Si3N4) as the ceramic substrate, the above-mentioned thermal cycling was carried out up to 20 cycles, and those in which no cracks were found after 20 cycles were indicated as ">20."

[0057] [Table 1]

[0058] [Table 2]

[0059] In Comparative Example 1, in which the heating rate in the temperature range of 450°C or more and less than 650°C was 2°C / min, and in Comparative Example 11, in which the heating rate in the temperature range of 450°C or more and less than 650°C was 1°C / min, the thickness of the active metal nitride layer was thinner than the range of the present invention, and the thermal cycle reliability was low. In Comparative Example 2, in which the heating rate in the temperature range of 450°C or more and less than 650°C was 30°C / min, and in Comparative Example 12, in which the heating rate in the temperature range of 450°C or more and less than 650°C was 35°C / min, the thickness of the active metal nitride layer was thicker than the range of the present invention, and the thermal cycle reliability was low.

[0060] Mg content 3.6 μmol / cm 2 Comparative Example 3 in which the Mg content was 7.2 μmol / cm 2 In Comparative Example 13, the thickness of the active metal nitride layer was thinner than the range of the present invention, and the thermal cycle reliability was low. Mg content 107.3 μmol / cm 2 Comparative Example 4, in which the Mg content was 114.4 μmol / cm 2 In Comparative Example 14, the thickness of the active metal nitride layer was greater than the range of the present invention, and the thermal cycle reliability was low.

[0061] The amount of active metal (Zr) is 0.2 μmol / cm 2 Comparative Example 5, in which the amount of active metal (Nb) was 0.3 μmol / cm 2 In Comparative Example 15, the thickness of the active metal nitride layer was thinner than the range of the present invention, and the thermal cycle reliability was low. The amount of active metal (Nb) is 21.3 μmol / cm 2 Comparative Example 6, in which the amount of active metal (Ti) was 24.4 μmol / cm 2 In Comparative Example 16, the thickness of the active metal nitride layer was greater than the range of the present invention, and the thermal cycle reliability was low.

[0062] Furthermore, Conventional Examples 1 and 11, which used a bonding material containing Ag and Ti, were rated "poor" for migration resistance.

[0063] In contrast, in Examples 1 to 9 and 11 to 19 of the present invention, in which the thickness of the active metal nitride layer was within the range of the present invention, cracking of the ceramic members was suppressed even when subjected to thermal cycling, and the ceramic members exhibited excellent thermal cycling reliability and migration resistance.

[0064] Example 2 As in Example 1, a ceramic substrate (40 mm×40 mm×0.635 mm) made of aluminum nitride (AlN) and a ceramic substrate (40 mm×40 mm×0.32 mm) made of silicon nitride (Si 3 N 4 ) were prepared. Copper plates (37 mm × 37 mm × 0.3 mm thick) made of oxygen-free copper were bonded to both sides of this ceramic substrate under the conditions shown in Tables 3 and 4 to obtain an insulated circuit board (copper / ceramic bonded body). The degree of vacuum in the vacuum furnace during bonding was 8 × 10 -3 It was Pa. Here, in Examples 21 to 25 of the present invention, a ceramic substrate made of aluminum nitride (AlN) was used, and in Examples 31 to 35 of the present invention, a ceramic substrate made of silicon nitride (Si3N4) was used.

[0065] The obtained insulating circuit board (copper / ceramic bonded body) was evaluated in the same manner as in Example 1 for the thickness of the active metal nitride layer at the bonded interface, the presence or absence of an Mg solid solution layer, and migration resistance. Furthermore, the presence or absence of Cu-containing particles in the active metal nitride layer and ultrasonic bonding were evaluated as follows.

[0066] (Presence or absence of Cu-containing particles) An observation sample was taken from the center of the obtained insulated circuit board (copper / ceramic bonded body), and the bonding interface between the copper plate and the ceramic substrate was observed using a scanning transmission electron microscope (FEI Titan ChemiSTEM (with EDS detector)) at magnifications of 40,000 to 115,000 times and an accelerating voltage of 200 kV. Mapping was performed using energy dispersive X-ray analysis (Thermo Scientific NSS7). An electron beam narrowed to about 1 nm was irradiated in the region where the active metal and N overlap (Nanobeam Diffraction (NBD) method) to obtain an electron diffraction pattern, and the active metal nitride layer was confirmed. Here, Cu-containing particles were determined to be "present" when Cu was detected in the region where the active metal and N overlapped. The equivalent circle diameter of the Cu-containing particles was 10 nm to 100 nm.

[0067] (Ultrasonic bonding evaluation) To the obtained insulating circuit board (copper / ceramic bonded body), copper terminals (10 mm × 5 mm × 1 mm thick for AlN, 10 mm × 10 mm × 1 mm thick for Si3N4) were ultrasonically bonded using an ultrasonic metal bonding machine (60C-904 manufactured by Ultrasonic Industrial Co., Ltd.) with a bonding depth of 0.5 mm. Ten copper terminals were bonded for each type. After bonding, the bonding interface between the copper plate and the ceramic substrate was inspected using an ultrasonic flaw detector (FSP8V manufactured by Hitachi Power Solutions Co., Ltd.). Those in which peeling between the copper plate and the ceramic substrate or ceramic cracks were observed in three or more out of ten were rated "C," those in which peeling between the copper plate and the ceramic substrate or ceramic cracks were observed in one to two out of ten were rated "B," and those in which no peeling between the copper plate and the ceramic substrate or ceramic cracks were observed in any of the ten were rated "A." The evaluation results are shown in Tables 3 and 4.

[0068] [Table 3]

[0069] [Table 4]

[0070] In Examples 22, 23, and 25 of the present invention and Examples 32, 33, 34, and 35 of the present invention, in which Cu-containing particles were confirmed inside the active nitride layer, the ultrasonic bonding evaluation was "A," and it was confirmed that it is possible to suppress peeling between the copper plate and the ceramic substrate and the occurrence of cracks in the ceramic substrate during ultrasonic bonding, compared to Examples 21, 24, and 31 of the present invention, in which Cu-containing particles were not observed.

[0071] As a result of the above, it was confirmed that the examples of the present invention can suppress the occurrence of cracks in ceramic members even when subjected to severe thermal cycles, and can provide a copper / ceramic bonded body, an insulated circuit board, and a method for manufacturing a copper / ceramic bonded body and an insulated circuit board that are excellent in migration resistance. [Explanation of symbols]

[0072] 10 Insulated circuit board (copper / ceramic bonded body) 11 Ceramic substrate (ceramic component) 12 Circuit layer (copper material) 13 Metal layer (copper material) 41 Active metal nitride layer

Claims

1. A copper / ceramic joined body obtained by joining a copper member made of copper or a copper alloy and a ceramic member made of a nitrogen-containing ceramic, At the bonding interface between the copper member and the ceramic member, an Mg solid solution layer in which Mg is solid-solved in a Cu matrix is ​​formed, and an active metal nitride layer containing nitrides of one or more active metals selected from Ti, Zr, Nb, and Hf is formed on the ceramic member side, a copper / ceramic joined body, characterized in that the thickness of the active metal nitride layer is in the range of 0.05 μm or more and 1.2 μm or less, and there is no region between the Mg solid solution layer and the ceramic member where the active metal nitride layer is not present.

2. 2. The copper / ceramic bonded article according to claim 1, wherein the active metal is Ti.

3. 3. The copper / ceramic bonded body according to claim 1, wherein Cu-containing particles are present inside the active metal nitride layer.

4. An insulating circuit board having a ceramic substrate made of nitrogen-containing ceramic and a copper plate made of copper or a copper alloy bonded to the surface thereof, At the bonding interface between the copper plate and the ceramic substrate, an Mg solid solution layer in which Mg is solid-solved in a Cu matrix is ​​formed, and an active metal nitride layer containing nitrides of one or more active metals selected from Ti, Zr, Nb, and Hf is formed on the ceramic substrate side, An insulating circuit board characterized in that the thickness of this active metal nitride layer is in the range of 0.05 μm or more and 1.2 μm or less, and there is no area between the Mg solid solution layer and the ceramic substrate where the active metal nitride layer is not present.

5. 5. The insulating circuit board according to claim 4, wherein the active metal is Ti.

6. 6. The insulating circuit board according to claim 4, wherein Cu-containing particles are present inside the active metal nitride layer.

7. A method for producing a copper / ceramic bonded body according to any one of claims 1 to 3, comprising the steps of: an active metal and Mg arranging step of arranging one or more active metals selected from Ti, Zr, Nb, and Hf and Mg between the copper member and the ceramic member; a lamination step of laminating the copper member and the ceramic member with an active metal and Mg interposed therebetween; a joining step of joining the copper member and the ceramic member, which are laminated via the active metal and Mg, by heat treatment in a vacuum atmosphere while applying pressure to the copper member and the ceramic member in a lamination direction; It is equipped with In the active metal and Mg arranging step, the amount of active metal is 0.4 μmol / cm ２ 18.8 μmol / cm or more ２ Within the following range, the Mg content is 14 μmol / cm ２ More than 86μmol / cm ２ Within the following range: the joining step is performed at a temperature rise rate of 5°C / min or more and 20°C / min or less in a temperature range of 450°C or more and less than 650°C, the holding temperature is in a range of 700°C or more and 850°C or less, and the holding time at the holding temperature is in a range of 10 min or more and 180 min or less.

8. A method for manufacturing an insulating circuit board according to any one of claims 4 to 6, comprising the steps of: an active metal and Mg arranging step of arranging one or more active metals selected from Ti, Zr, Nb, and Hf and Mg between the copper plate and the ceramic substrate; a lamination step of laminating the copper plate and the ceramic substrate via an active metal and Mg; a bonding step of bonding the copper plate and the ceramic substrate, which are laminated via the active metal and Mg, by heat treatment in a vacuum atmosphere while applying pressure to the copper plate and the ceramic substrate in the lamination direction; It is equipped with In the active metal and Mg arranging step, the amount of active metal is 0.4 μmol / cm ２ 18.8 μmol / cm or more ２ Within the following range, the Mg content is 14 μmol / cm ２ More than 86μmol / cm ２ Within the following range: a temperature rise rate of 5°C / min or more and 20°C / min or less in a temperature range of 450°C or more and less than 650°C in the bonding step, a holding temperature of 700°C or more and 850°C or less, and a holding time at the holding temperature of 10 minutes or more and 180 minutes or less.

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