Method for manufacturing joint body for insulating circuit substrate and joint body for insulating circuit substrate

Abstract

The manufacturing method of the assembly for insulating circuit substrate of the present invention comprises: an aluminum circuit layer forming step, forming multiple aluminum circuit layers on one surface of a ceramic substrate; and a copper circuit layer forming step, laminating copper plates for circuit layers on each of the aluminum circuit layers, arranging the stacked body between a pair of pads having convex surfaces on at least one surface and arranging these convex surfaces opposite to each other, pressurizing the stacked body in the stacking direction by moving the pads in opposite directions, and heating the stacked body in the pressurized state, thereby forming a copper circuit layer in which the copper plates for circuit layers are solid-phase diffusion-bonded to the aluminum circuit layer. In the copper circuit layer forming step, the pads are arranged in such a way that any one of the convex surfaces spans and abuts against the adjacent multiple copper plates for circuit layers in the stacked body.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an insulating circuit substrate assembly such as a power module substrate used in a semiconductor device that controls a large current and a high voltage, and an insulating circuit substrate assembly. This application claims priority based on Japanese Patent Application No. 2018-58136 filed on March 26, 2018, and the contents thereof are incorporated herein by reference. Background Art

[0002] As a power module substrate, there is known a substrate in which a circuit layer is bonded to one surface of an insulating layer composed of a ceramic substrate represented by aluminum nitride, and a metal layer for heat dissipation is bonded to the other surface, and a heat sink is bonded to the metal layer.

[0003] For example, the substrate for a power module with a heat sink disclosed in Patent Document 1 has a circuit layer with a double-layer structure of an aluminum layer and a copper layer formed on one surface of an insulating layer formed by a ceramic substrate, a metal layer with a double-layer structure of an aluminum layer and a copper layer bonded to the other surface of the ceramic substrate (insulating layer), and a heat sink formed of aluminum is bonded to the copper layer of the metal layer.

[0004] In the manufacturing method of the substrate for power module with heat sink, aluminum plates are first brazed on both sides of the ceramic substrate, and then a copper plate is stacked on one side, and the copper plate and the aluminum plate of the heat sink are stacked on the other side. The stack is heated while being pressed in the stacking direction, thereby solid phase diffusion bonding of aluminum and copper. At this time, in Patent Document 1, the bonding surface of the heat sink is formed into a convex shape to match the warping of the metal layer surface of the power module substrate caused by the bonding temperature of the heat sink.

[0005] In this solid phase diffusion bonding, the stack is arranged between a pair of pressure plates urged by springs, and a fixing plate fixed to a pair of guide posts provided outside the outer periphery of the ceramic substrate is used to apply force to bring the pressure plates closer together, thereby applying a load to the stack.

[0006] Patent Document 1: Japanese Patent Application Publication No. 2016-72563

[0007] However, since the guide post cannot be arranged directly above the stack, it tends to be difficult to apply a load on the inner side than the outer periphery of the ceramic substrate. The bonding between the ceramic substrate and the aluminum plate is roughly uniform over the entire surface because a liquid phase is generated by brazing, but since the aluminum layer and the copper layer are solid-phase bonded, their contact state has a great influence on the bonding. In the bonding using the above-mentioned pressure plate, the load tends to be concentrated on the outer periphery of the circuit layer, and conversely, it is difficult to apply a load on the inner side than the outer periphery, and poor bonding may occur outside the outer periphery of the metal layer. In particular, when the circuit layer is separated into a plurality of circuit layers, a sufficient intermetallic compound layer generated by solid-phase diffusion bonding is not formed in the inner end of the copper plate of the adjacent circuit layer facing the gap, and poor bonding is likely to occur. Summary of the invention

[0008] The present invention has been developed in view of such circumstances, and an object of the present invention is to apply a uniform load to the end portions of the adjacent circuit layer copper plates facing the inner side of the gap, thereby preventing the occurrence of poor bonding.

[0009] The manufacturing method of the assembly for insulating circuit substrate of the present invention comprises: an aluminum circuit layer forming step, forming multiple aluminum circuit layers on one surface of a ceramic substrate; and a copper circuit layer forming step, laminating copper plates for circuit layers on each of the aluminum circuit layers, arranging the stacked body between a pair of pads having convex surfaces on at least one surface and arranging these convex surfaces opposite to each other, pressurizing the stacked body in the stacking direction by moving the pads in opposite directions, and heating the stacked body in the pressurized state, thereby forming a copper circuit layer in which the copper plates for circuit layers are solid-phase diffusion-bonded to the aluminum circuit layer. In the copper circuit layer forming step, the pads are arranged in such a way that any one of the convex surfaces spans and abuts against the adjacent multiple copper plates for circuit layers in the stacked body.

[0010] According to this manufacturing method, in the copper circuit layer forming process, since the convex surface of the pad spans across and abuts against the adjacent circuit layer copper plate, it is easy to apply load to the end of the circuit layer copper plate in the central part of the ceramic substrate, which was previously difficult to apply load to, just like the peripheral end.

[0011] In a preferred embodiment of the method for manufacturing an insulating circuit substrate assembly of the present invention, the convex surface of the backing plate may have a radius of curvature of 8000 mm or more and 60000 mm or less. If the radius of curvature is within this range, an intermetallic compound layer can be formed with sufficient thickness until the end of the adjacent copper circuit layer, thereby obtaining good bonding.

[0012] In a preferred embodiment of the method for producing an insulating circuit board assembly of the present invention, the backing plate may be composed of a carbon material sheet. In addition, the carbon material sheet may be a laminate of one or more carbon sheets and one or more graphite sheets.

[0013] By using a carbon material sheet, the adhesion between the backing plate and the laminate can be prevented. In addition, due to the cushioning property of the carbon material sheet, a gentle pressure gradient can be obtained in which the load gradually increases from the outer peripheral side of the convex surface to the central part, so that the copper plate for the circuit layer can be pressed more evenly over the entire surface and bonded.

[0014] In the method for producing an insulating circuit board assembly of the present invention, the convex surface may be a spherical surface or a cylindrical surface. The shape of the convex surface may be appropriately set according to the number or arrangement of the copper plates for the circuit layer of the laminate.

[0015] In the assembly for insulating circuit substrate of the present invention, the one surface of the pad can be the convex curved surface, and the other surface can be a flat surface. For example, in the outermost pad disposed in a plurality of stacked bodies sandwiching the pads, the surface that does not press the copper plate for the circuit layer can also be a flat surface, and the entire surface of the flat surface can bear the pressing force from the pressure plate.

[0016] Regarding a preferred embodiment of the manufacturing method of an insulating circuit substrate assembly of the present invention, a pair of the pads can be arranged between a pair of pressure plates opposite to each other in the stacking direction, so that the pair of pressure plates can be maintained close to or away from each other along the stacking direction by at least two guide pillars extending along the stacking direction, and by bringing the pair of pressure plates close to each other, the stacked body is pressurized through the pair of pads.

[0017] It is difficult to uniformly pressurize the stacked body between a pair of pressurizing plates held by two guide pins. However, by using the convex surface of the pad, a sufficient load can be applied to the center of the stacked body.

[0018] The insulating circuit substrate joint body of the present invention comprises: a ceramic substrate; a plurality of aluminum circuit layers bonded to one surface of the ceramic substrate; a copper circuit layer solid phase diffusion bonded to each of the aluminum circuit layers; and an intermetallic compound layer between each of the aluminum circuit layers and each of the copper circuit layers. Regarding the intermetallic compound layer, when the average thickness on the central side of the boundary is set to t1 and the average thickness on the end side of the boundary is set to t2, with the position 50 μm from the end of the adjacent copper circuit layer facing the gap as the boundary, the ratio t2 / t1 of their thicknesses is greater than 30%.

[0019] Since the average thickness t2 of the intermetallic compound layer in the portion facing the gap of the plurality of copper circuit layers is 30% or more of the average thickness of the intermetallic compound layer closer to the center, sufficient solid phase diffusion bonding can be achieved up to the end portions, and a sufficient bonding state can be maintained.

[0020] The insulating circuit substrate assembly can be used directly as an insulating circuit substrate having a plurality of circuit layers, or can be used as an insulating circuit substrate unit by forming scribe lines on a ceramic substrate between adjacent copper circuit layers and dividing the ceramic substrate.

[0021] According to the present invention, a uniform load can be applied also to the end portions of the adjacent copper circuit layers facing the inside of the gap, thereby preventing the occurrence of bonding failure. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a side view showing a joined body for an insulating circuit board manufactured by the manufacturing method for a joined body for an insulating circuit board according to the embodiment of the present invention.

[0023] Figure 2 yes Figure 1 A top view of a bonded body for an insulating circuit substrate is shown.

[0024] Figure 3A It is a side view which shows the manufacturing method of the bonded body for insulating circuit boards in order of process.

[0025] Figure 3B It is a side view which shows the manufacturing method of the bonded body for insulating circuit boards in order of process.

[0026] Figure 3C It is a side view which shows the manufacturing method of the bonded body for insulating circuit boards in order of process.

[0027] Figure 3D It is a side view which shows the manufacturing method of the bonded body for insulating circuit boards in order of process.

[0028] Figure 4 It is a side view of the pressurizing device.

[0029] Figure 5 yes Figure 4 AA view.

[0030] Figure 6 It is a plan view showing an insulating circuit substrate assembly (power module substrate) according to another embodiment.

[0031] Figure 7 This is a cross-sectional micrograph of the vicinity of the interface between the aluminum layer and the copper layer at the end of the circuit layer of Sample 4.

[0032] Figure 8 This is a cross-sectional micrograph of the vicinity of the interface between the aluminum layer and the copper layer at the end of the circuit layer of Sample 10. DETAILED DESCRIPTION

[0033] Hereinafter, embodiments of the present invention will be described. Figure 1 and Figure 2 As an example of an insulating circuit substrate assembly manufactured by the manufacturing method of the present invention, an insulating circuit substrate assembly 10 is shown for manufacturing a plurality of power module substrates (insulating circuit substrates) 1. In the example shown, four power module substrates 1 can be manufactured.

[0034] The assembly 10 for insulating circuit substrates has a ceramic substrate 11, a plurality of circuit layers 12 bonded to one surface (front surface) of the ceramic substrate 11, and a plurality of heat dissipation layers 13 bonded to the other surface (back surface) of the ceramic substrate 11. With respect to the plane dimensions, each circuit layer 12 is a square with each side being 5 mm or more and 100 mm or less, and the gap g between each circuit layer 12 is 1 mm or more and 20 mm or less. In the present embodiment, the heat dissipation layer 13 is also arranged with the same gap g.

[0035] The ceramic substrate 11 is an insulating material that prevents electrical connection between the circuit layer 12 and the heat dissipation layer 13, and is made of, for example, aluminum nitride (AlN), silicon nitride (Si 3 N 4 ) etc., and the plate thickness is 0.2mm to 1.5mm.

[0036] In the present embodiment, the scribe line 15 for dividing the ceramic substrate 11 into four is formed in a cross shape in plan view on the ceramic substrate 11 .

[0037] The circuit layer 12 and the heat dissipation layer 13 both have a double-layer structure of an aluminum layer made of aluminum or an aluminum alloy and a copper layer made of copper or a copper alloy.

[0038] In this case, in the circuit layer 12 , the aluminum circuit layer 121 and the copper circuit layer 122 are bonded in a stacked state in each region divided by the scribe line 15 , and the scribe line 15 is formed on the ceramic substrate 11 along the gap g between adjacent circuit layers 12 .

[0039] The aluminum layer serving as the circuit layer 12 is referred to as an aluminum circuit layer 121 , and the aluminum layer serving as the heat dissipation layer 13 is referred to as an aluminum heat dissipation layer 131 . However, unless otherwise specifically distinguished, they are simply referred to as aluminum layers.

[0040] Aluminum or aluminum alloy can be used for these aluminum layers 121 and 131, but pure aluminum with a purity of 99.00 mass % or more or 99.99 mass % or more is preferred to relax stress. In addition, the thickness of these aluminum layers 121 and 131 is preferably 0.1 mm to 1.0 mm. The aluminum circuit layer 121 and the aluminum heat dissipation layer 131 can have the same thickness or different thicknesses.

[0041] These aluminum layers 121 and 131 are formed by laminating aluminum plates on both surfaces of the ceramic substrate 11 via, for example, an Al—Si-based brazing material, and bonding them by brazing by applying pressure and heating in the laminating direction.

[0042] On the other hand, for the copper layer of the circuit layer 12 and the copper layer of the heat dissipation layer 13, similarly to the aluminum layer, the copper layer of the circuit layer 12 is set as the copper circuit layer 122, and the copper layer of the heat dissipation layer 13 is set as the copper heat dissipation layer 132, but when there is no special distinction, they are simply referred to as copper layers.

[0043] Copper or copper alloy can be used for these copper layers 122 and 132, but oxygen-free copper is preferred. The plane size can be the same as that of the aluminum layer, but in the example shown in the figure, it is formed to be slightly smaller than the aluminum layer. The plate thickness is preferably greater than 0.1 mm and less than 6.0 mm, and the copper circuit layer 122 and the copper heat dissipation layer 132 can be the same thickness or different thicknesses.

[0044] The copper circuit layer 122 is formed by solid phase diffusion bonding a copper plate to each aluminum circuit layer 121 , and the copper heat dissipation layer 132 is formed by solid phase diffusion bonding a copper plate to the aluminum heat dissipation layer 131 .

[0045] Next, a method for manufacturing the insulating circuit substrate assembly 10 will be described. Figures 3A to 3D As shown, the scribing process ( Figure 3A )、Aluminum layer bonding process ( Figure 3B )、Copper layer bonding process ( Figure 3C ) and the segmentation process ( Figure 3D ) order to manufacture.

[0046] (Scribe Line Formation Process)

[0047] Scribe lines 15 are formed on the ceramic substrate 11 for dividing the substrates 1 into a plurality of power module substrates. Figure 3A As shown, the scribe line 15 can be formed by laser processing. Specifically, the surface of the ceramic substrate 11 is irradiated with CO 2 The scribe line 15 is processed by laser light L such as laser light, YAG laser, YVO4 laser, YLF laser, or the like.

[0048] (Aluminum layer forming step (aluminum circuit layer forming step))

[0049] like Figure 3B As shown, on the surface of the ceramic substrate 11, a plurality of aluminum plates 21 for circuit layers are stacked via a brazing foil 50, and on the back side of the ceramic substrate 11, a plurality of aluminum plates 31 for heat dissipation layers are stacked via a brazing foil 50. The plurality of aluminum plates 21 for circuit layers and the plurality of aluminum plates 31 for heat dissipation layers are stacked in respective formation areas divided by the scribe lines 15 of the ceramic substrate 11. Here, the brazing uses the brazing foil 50, but the brazing paste may be applied to the surface of the ceramic substrate 11.

[0050] Then, the laminate of the circuit layer aluminum plate 21, the heat dissipation layer aluminum plate 31, the ceramic substrate 11, and the brazing foil 50 is brazed by heating to 640°C to 650°C while being pressurized in the lamination direction in a vacuum atmosphere.

[0051] Thus, a plurality of aluminum circuit layers 121 are formed on one surface of the ceramic substrate 11 , and a plurality of aluminum heat dissipation layers 131 are formed on the other surface.

[0052] (Copper layer forming step (copper circuit layer forming step))

[0053] like Figure 3C As shown, the circuit layer copper plate 22 is stacked on each aluminum circuit layer 121 bonded to the surface of the ceramic substrate 11. In the same manner, the heat dissipation layer copper plate 32 is stacked on the aluminum heat dissipation layer 131 bonded to the back surface of the ceramic substrate 11.

[0054] The circuit layer copper plate 22 is laminated on each of the plurality of aluminum circuit layers 121. The heat dissipation layer copper plate 32 is also laminated on each of the plurality of aluminum heat dissipation layers 131.

[0055] Then, the stacked body 40 is heated at a temperature lower than the eutectic temperature of copper and aluminum while being pressurized in the stacking direction, thereby solid phase diffusion bonding is performed between each aluminum circuit layer 121 and the circuit layer copper plate 22, and between the aluminum heat dissipation layer 131 and the heat dissipation layer copper plate 32.

[0056] Figure 4 and Figure 5 : represents a pressurizing device 60 used in the solid phase diffusion bonding. The pressurizing device 60 comprises a bottom plate (fixed side pressurizing plate) 61, a plurality of guide posts 62 vertically mounted on the top of the bottom plate 61, a backing plate 63 supported movably along the guide posts 62 at the upper ends of the guide posts 62, a pressurizing plate (movable side pressurizing plate) 64 supported movably up and down on the guide posts 62 between the bottom plate 61 and the backing plate 63, and a biasing mechanism 65 such as a spring provided between the backing plate 63 and the pressurizing plate 64 and biasing the pressurizing plate 64 downward. The backing plate 63 and the pressurizing plate 64 are arranged parallel to the bottom plate 61.

[0057] At least two guide posts 62 are vertically provided on the bottom plate 61. A threaded portion 62a is formed at the upper end of each guide post 62, and a nut 66 is screwed into the threaded portion 62a on the back support plate 63. In this embodiment, a plurality of stacked bodies 40 are arranged in an overlapping manner between the bottom plate 61 and the pressure plate 64. In this case, the stacked bodies 40 are arranged on the inner side of the guide posts 62, and by screwing the nut 66 into the threaded portion 62a of the guide posts 62, pressure is applied between the two pressure plates 61 and 64 in the stacking direction.

[0058] In addition, the guide posts 62 are not limited to two, and one guide post 62 may be provided at each of the four corners of the upper surface of the bottom plate 61, and a total of four guide posts 62 may be provided. Furthermore, a group of stacked bodies in the stacked bodies 40 may be arranged between the bottom plate 61 and the pressurizing plate 64. Although pressurization is performed by screwing the nut 66 into the threaded portion 62a of the guide post 62, the pressurization method is not limited to this structure, and hot pressing or the like may also be used.

[0059] In this step, in order to allow the pressing force to act effectively on the center portion of the stacked body 40 in the surface direction, the backing plates 70 are arranged on both surfaces of the stacked body 40 .

[0060] Both surfaces of the pad 70 are formed into convex curved surfaces 70a. The convex curved surface 70a is set as a curved surface with a curvature radius R of 8000 mm or more and 60000 mm or less.

[0061] The pad 70 is arranged so that the convex surface 70a (see FIG. 3 ) is opposite to the gap g between the adjacent circuit layers 12 and the gap g between the heat dissipation layer 13 of the laminate 40. In addition, the surface of the pad 70 that is not in contact with the circuit layer 12 (for example, the surface in contact with the bottom plate 61 or the pressure plate 64) may be a flat surface.

[0062] In the present embodiment, the rectangular circuit layer 12 is configured as four in a top view with one corner close to each other, so the convex surface 70a is formed into a spherical shape that is most prominent in the part gathered at the four corners, but depending on the number of circuit layers 12 configured, a cylindrical surface can be used in addition to a spherical surface. For example, when two circuit layers are arranged side by side, the convex surface is formed into a cylindrical surface so that the axial direction of the cylinder is arranged along the gap between the two circuit layers. In addition to the spherical surface and the cylindrical surface, a curved surface such as the surface of a rotating ellipsoid may also be used. Within the range of its radius of curvature R = 8000mm to 60000mm, it may also be made into a structure with a single radius of curvature or a combination of multiple radii of curvature, which can be appropriately set according to the number or configuration of the circuit layers.

[0063] The pad 70 is made of a carbon material sheet. As the carbon material sheet, for example, a laminate of a carbon sheet and a graphite sheet can be used. For example, the carbon sheet can use G-347 manufactured by ASAHI-GRAPHITE (thermal conductivity 116 W / mK, elastic modulus 10.8 GPa). For example, the graphite sheet can use T-5 manufactured by ASAHI-GRAPHITE (thermal conductivity 75.4 W / mK, elastic modulus 11.4 GPa) or graphite sheet PF manufactured by Toyo Tanso Co., Ltd. (compression rate 47%, recovery rate 14%), etc.

[0064] In the pressurizing device 60 thus configured, the plurality of laminates 40 are arranged with the backing plate 70 interposed therebetween. In this case, the plurality of laminates 40 are arranged so that the convex surface 70a of the backing plate 70 abuts against the circuit layer copper plate 22 and the heat dissipation layer copper plate 32 of each laminate 40.

[0065] Then, the pressure is maintained at a pressure of not less than 0.3 MPa and not more than 3.5 MPa, and the heating temperature is maintained at not less than 400°C and not more than 548°C in a vacuum environment for not less than 5 minutes and not more than 240 minutes, thereby, the copper plate 22 for the circuit layer and the copper plate 32 for the heat dissipation layer are respectively joined to the aluminum circuit layer 121 and the aluminum heat dissipation layer 131 through solid phase diffusion of copper and aluminum.

[0066] According to the thus manufactured insulating circuit substrate assembly 10, an aluminum circuit layer 121 and a copper circuit layer 122 are sequentially bonded in a stacked state on one surface of a ceramic substrate 11, and an aluminum heat dissipation layer 131 and a copper heat dissipation layer 132 are sequentially bonded in a stacked state on the other surface of the ceramic substrate 11.

[0067] Then, an intermetallic compound layer M (see FIG. 1 ) produced by solid phase diffusion bonding of aluminum and copper is formed between the aluminum circuit layer 121 and the copper circuit layer 122 and between the aluminum heat dissipation layer 131 and the copper heat dissipation layer 132. Figure 7 ).

[0068] In the copper plate bonding process, the convex surface 70a of the pad 70 is brought into contact with the circuit layer copper plate 22 and the heat dissipation layer copper plate 32 and pressurized, thereby forming an intermetallic compound layer M with a substantially uniform thickness on the entire surface between the aluminum circuit layer 121 and the copper circuit layer 122 and between the aluminum heat dissipation layer 131 and the copper heat dissipation layer 132.

[0069] The average thickness of the intermetallic compound layer M is greater than 12 μm and less than 40 μm. When the average thickness closer to the center than the boundary is set to t1 and the average thickness closer to the end than the boundary is set to t2, the ratio t2 / t1 of their thicknesses is greater than 30%.

[0070] (Separation process)

[0071] Finally, if Figure 3D As shown, the ceramic substrate 11 is divided into a plurality of pieces along the scribe lines 15 .

[0072] As described above, according to the manufacturing method of this embodiment, by making the convex surface 70a of the pad 70 abut against the copper plate 22 for the circuit layer and the copper plate 32 for the heat dissipation layer and applying pressure, an intermetallic compound layer M produced by solid phase diffusion bonding can be formed on the entire surface with a roughly uniform thickness between the aluminum circuit layer 121 and the copper circuit layer 122, and between the aluminum heat dissipation layer 131 and the copper heat dissipation layer 132, without causing poor bonding and enabling strong bonding.

[0073] In this case, if the radius of curvature R of the convex surface 70a is less than 8000 mm, the radius of curvature is too small, so the load is too concentrated near the ends of the copper circuit layer 122 and the copper heat dissipation layer 132 facing the gap g, and on the contrary, the load near the outer peripheral edge is insufficient, which may cause poor bonding at the outer peripheral edge. If the radius of curvature R of the convex surface 70a exceeds 60000 mm, it will be close to a plane, so the improvement effect of bonding near the ends of the copper circuit layer 122 and the copper heat dissipation layer 132 facing the gap g is poor.

[0074] In addition, the above embodiment is a method of manufacturing a plurality of power module substrates 1 by forming the scribe line 15 on the ceramic substrate 11. However, even when manufacturing one power module substrate (insulating circuit substrate) 1 using the ceramic substrate 11 without the scribe line 15 ( Figure 6 ), the present invention is still applicable when the circuit layer 12 is separated into multiple layers.

[0075] about Figure 6 In the insulated circuit substrate assembly 100, on one surface of a ceramic substrate 11, a circuit layer 12 is formed in a state of being separated into two, and a copper circuit layer 122 is bonded to each other in a laminated state via an aluminum circuit layer 121. On the other surface of the ceramic substrate 11, a heat dissipation layer 13 is formed, and a copper heat dissipation layer 132 is bonded to each other in a laminated state via an aluminum heat dissipation layer 131.

[0076] In the joint body 100 for insulating circuit substrate, after the aluminum circuit layer 121 and the aluminum heat dissipation layer 131 are formed in a bonded state by brazing on the ceramic substrate 11, the circuit layer copper plate 22 is solid-phase diffusion-bonded to the aluminum circuit layer 121, and the heat dissipation layer copper plate 32 is solid-phase diffusion-bonded to the aluminum heat dissipation layer 131. At this time, by applying pressure using the pad 70 having the convex surface 70a, it is possible to apply pressure also to the vicinity of the end of the circuit layer copper plate 22 facing the gap g, thereby forming the copper circuit layer 122 firmly bonded to the aluminum circuit layer 121.

[0077] In this case, each circuit layer 12 has a square shape with a planar size of 5 mm to 100 mm, and a gap g between the circuit layers 12 is set to 1 mm to 20 mm.

[0078] The insulating circuit substrate assembly 100 is used as a power module substrate (insulating circuit substrate) 1 as it is after the copper circuit layer 122 and the copper heat dissipation layer 132 are formed.

[0079] In addition, the present invention can be applied to a case where a circuit layer having a double-layer structure of an aluminum layer and a copper layer is formed on one surface of a ceramic substrate, or a case where the other surface of the ceramic substrate does not have a double-layer heat dissipation layer as in the embodiment.

[0080] Example

[0081] As the aluminum plate joining process, two aluminum plates (38mm×38mm, 4N-Al with a thickness of 0.25mm) were stacked at a distance of 2mm on the surface of a ceramic substrate (40mm×80mm, AlN with a thickness of 0.635mm) forming an insulating layer, and an aluminum plate (38mm×78mm, 4N-Al with a thickness of 0.25mm) was stacked on the other side of the ceramic substrate, and the aluminum layers were formed by brazing. As the brazing material, Al-Si brazing foil (thickness 14μm) was used, and a pressure of 0.3MPa was applied in the stacking direction, and the bonding was performed by heating at a temperature of 640°C for 40 minutes.

[0082] As a copper plate bonding process, a copper plate (37 mm × 37 mm, 0.3 mm thick, oxygen-free copper) was positioned and stacked on the aluminum layer formed on the surface of the ceramic substrate, and a copper plate (37 mm × 77 mm, 0.3 mm thick, oxygen-free copper) was stacked on the aluminum layer formed on the back of the ceramic substrate. Pads with various curvature radii shown in Table 1 were used, a pressure of 1 MPa was applied in the stacking direction, and the plates were heated at 540°C for 90 minutes in a vacuum environment to perform solid phase diffusion bonding.

[0083] According to the samples 1 to 11 prepared in this way, the cross section passing through the approximate center of the circuit layer and approximately perpendicular to the end surface was observed under a microscope to confirm the intermetallic compound layer between the aluminum layer and the copper layer in the circuit layer. The average thickness t1 of the intermetallic compound layer closer to the center than the position 50 μm from the end of the adjacent circuit layer facing the gap, and the average thickness t2 of the intermetallic compound layer closer to the end than the position 50 μm from the end were measured, and the thickness ratio t2 / t1 was calculated.

[0084] In addition, as an evaluation of bonding properties, solder was placed on the copper circuit layers of the obtained samples 1 to 11, and after reflow at 285° C. for 10 minutes, solder was placed along the Figure 2The intermetallic compound layer was confirmed by microscopic observation of the cross-section along the BB line (a line passing through the approximate center of the circuit layer and approximately orthogonal to the end face). The intermetallic compound layer at the end was observed by a VK-X210 microscope made by KEYENCE CORPORATION at 20 times, and the case where the intermetallic compound layer at the end was confirmed to be damaged (cracked) was set as "bad", and the case where no crack was confirmed was set as "good". These results are shown in Table 1.

[0085] [Table 1]

[0086]

[0087] The bondability of samples 1 to 8, in which the radius of curvature R of the convex surface was 8000 mm to 60000 mm, was evaluated as “good.” In this case, the thickness ratio of the intermetallic compound layer was 33.3% or more, and a good result was considered to be obtained when it was 30% or more.

[0088] Figure 7 This is a microscope photograph of a cross section along line BB at the end of the aluminum layer and the copper layer of sample 4 before solder reflow. Figure 8 This is a microscope photograph of the sample 10 before solder reflow. Figure 7 The intermetallic compound layer M is formed to the edge of the end portion to join the aluminum layer and the copper layer. Figure 8 Unjoined portions appear at the edges of the ends.

[0089] Industrial Applicability

[0090] In the bonded structure for an insulating circuit board, a uniform load can be applied also to the end portions of the adjacent copper circuit layers facing the inside of the gap, thereby preventing the occurrence of bonding failure.

[0091] Explanation of symbols

[0092] 1 Power module substrate (insulated circuit substrate)

[0093] 10 Insulated circuit board joint

[0094] 11 Ceramic Substrate

[0095] 12 Circuit layer

[0096] 13 Heat dissipation layer

[0097] 15 Strike

[0098] 21 Aluminum plate for circuit layer

[0099] 22 Copper plate for circuit layer

[0100] 31 Aluminum plate for heat dissipation layer

[0101] 32 Copper plate for heat dissipation layer

[0102] 40 laminate

[0103] 50 solder foil

[0104] 60 Pressurizing device

[0105] 61 Bottom plate (fixed side pressure plate)

[0106] 62 Guide column

[0107] 62a Threaded part

[0108] 63 Back support plate

[0109] 64 Pressure plate (movable side pressure plate)

[0110] 65 Nut

[0111] 70 Pad

[0112] 70a Convex surface

[0113] 100 Insulated circuit substrate assembly (power module substrate)

[0114] 121 Aluminum circuit layer (aluminum layer)

[0115] 122 Copper circuit layer (copper layer)

[0116] 131 Aluminum heat dissipation layer (aluminum layer)

[0117] 132 Copper heat dissipation layer (copper layer)

[0118] M Intermetallic compound layer

Claims

1. A method for producing a joint body for an insulating circuit substrate, characterized in that: have: an aluminum circuit layer forming step of forming a plurality of aluminum circuit layers on one surface of the ceramic substrate, wherein a gap between the plurality of aluminum circuit layers is greater than or equal to 1 mm and less than or equal to 20 mm; and The copper circuit layer forming step comprises laminating copper plates for circuit layers on the respective aluminum circuit layers, pressurizing the laminated body, and heating the laminated body under the pressurized state to form a copper circuit layer in which the copper plates for circuit layers are solid phase diffusion bonded to the aluminum circuit layers. Wherein, the copper circuit layer forming process comprises: A configuration step, configuring the stacked body between a pair of pads having convex surfaces on at least one surface and the convex surfaces are arranged opposite to each other, and configuring the pads in a manner that any one of the convex surfaces is opposite to the gap between the plurality of adjacent copper plates for the circuit layers in the stacked body and straddles and abuts against the copper plates for the circuit layers; and The heating and pressurizing step is a step of pressurizing the stacked body in a stacking direction by moving the cushion plate in an opposing direction after the arranging step, and heating the stacked body in the pressurized state.

2. The method for producing a bonded body for an insulating circuit substrate according to claim 1, wherein: The convex surface of the pad has a curvature radius of not less than 8000 mm and not more than 60000 mm.

3. The method for producing a bonded body for an insulating circuit substrate according to claim 1, wherein: The backing plate is made of a carbon material sheet.

4. The method for producing a bonded body for an insulating circuit substrate according to claim 3, wherein: The carbon material sheet is a laminated plate of one or more carbon sheets and one or more graphite sheets.

5. The method for producing a bonded body for an insulating circuit substrate according to claim 1, wherein: The one surface of the pad is the convex curved surface, and the other surface is a flat surface.

6. The method for producing a bonded body for an insulating circuit substrate according to claim 1, wherein: The convex surface is a spherical surface.

7. The method for producing a bonded body for an insulating circuit substrate according to claim 1, wherein: The convex surface is a cylindrical surface.

8. The method for producing a joint body for an insulating circuit substrate according to any one of claims 1 to 7, characterized in that: The pair of the pads are arranged between a pair of pressure plates that are opposed to each other in the stacking direction. A pair of the pressurizing plates are held by at least two guide posts arranged along the stacking direction so as to be close to or away from each other along the stacking direction. In the copper circuit layer forming step, the laminated body is pressurized via the pair of pads by bringing the pair of press plates close to each other.

9. A joint body for an insulating circuit substrate, characterized in that: have: Ceramic substrate; A plurality of aluminum circuit layers are bonded to one surface of the ceramic substrate, and a gap between the plurality of aluminum circuit layers is greater than or equal to 1 mm and less than or equal to 20 mm; A plurality of copper circuit layers are solid phase diffusion bonded to each of the aluminum circuit layers; and an intermetallic compound layer between each of the aluminum circuit layers and each of the copper circuit layers, Regarding the intermetallic compound layer, the average thickness of the intermetallic compound layer is greater than 12 μm and less than 40 μm, and when a position 50 μm from the end of the adjacent copper circuit layer facing the gap is used as a boundary, the average thickness closer to the center than the boundary is set to t1, and the average thickness closer to the end than the boundary is set to t2, their thickness ratio t2 / t1 is greater than 30%.

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