Manufacturing method of metal base circuit board and metal base circuit board

Abstract

To provide a metal base circuit board having an improved withstand voltage characteristic and a manufacturing method of the same.SOLUTION: A manufacturing method of a metal base circuit board, comprises: a first laminating step of arranging a thermosetting resin sheet on a metal base plate and placing a first bonding spacer made of a rubber sheet including a reinforcing member on the thermosetting resin sheet; and a first bonding step of heating the metal base plate and the thermosetting resin sheet in a state of being pressurized via the first bonding spacer in a laminating direction of the metal base plate and the thermosetting resin sheet, and bonding the metal base plate and the thermosetting resin sheet to obtain a first bonded body; a second laminating step of arranging a metal plate on a surface of a thermosetting resin sheet of a first bonded body and mounting a second bonding spacer made of a rubber sheet including a reinforcing member on the metal plate; and a second bonding step of bonding the metal plate and the first bonded body by heating in a state of being pressurized via the second bonding spacer in the laminating direction of the metal plate and the first bonded body.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a metal-based circuit board, and to a metal-based circuit board. [Background technology]

[0002] Metal base circuit boards are used as components in power modules, LED modules, thermoelectric modules, etc., where power semiconductor elements, LED elements, and thermoelectric elements are bonded onto a circuit pattern made of a metal plate of the metal base circuit board.

[0003] To improve the heat dissipation characteristics of semiconductor elements, circuit patterns may require relatively thick metal plates of 1 mm or more. When manufacturing metal-based circuit boards, if the metal plate is thick and the circuit pattern is created by etching, the etching process must be carried out for a long time, and etching can cause sagging or skirts at the edges of the circuit pattern, making it difficult to achieve high dimensional accuracy.

[0004] For this reason, for example, in the metal base circuit board described in Patent Document 1, a conductive circuit section formed by punching a conductive metal plate is laminated and integrated onto at least one surface of a metal substrate (metal base plate) via an insulating layer. Also proposed is a method for manufacturing a metal base circuit board, which comprises punching out a portion of the metal base substrate and a holding plate having approximately the same outer dimensions as the metal substrate into the shape of a conductive circuit, fitting a conductive circuit section formed by punching a conductive metal plate into the punched hole, then placing the holding plate with the fitted conductive circuit section on at least one surface of the metal substrate via an insulating layer, laminating and integrating the two, and then peeling off only the holding plate from the insulating layer.

[0005] Patent Document 2 also proposes a method for manufacturing an insulated circuit board (metal-base circuit board), which includes a resin composition disposing step of disposing a resin composition containing a thermosetting resin on one surface of a metal substrate (metal base plate); a metal piece and pressing jig disposing step of disposing a plurality of metal pieces on the resin composition and disposing a pressing jig in areas other than the metal pieces; and a resin curing step of applying pressure to the metal substrate, the resin composition, the metal pieces, and the pressing jig in the stacking direction and heating them to cure the resin composition, wherein at least the pressing surface of the pressing jig that presses the resin composition is made of a resin whose SP value differs from that of the thermosetting resin by 3 or more.

[0006] Furthermore, Patent Document 3 discloses an insulated circuit board (metal-based circuit board) including a metal substrate (metal base plate), an insulating resin layer composed mainly of a thermosetting resin formed on one surface of the metal substrate, and a circuit layer having a circuit pattern formed on the surface of the insulating resin layer opposite the metal substrate, wherein the circuit layer is made of a metal material and has a thickness of 0.05 mm to 2.0 mm, and in a cross section along the stacking direction, the shape of an end face near the joint interface between the circuit layer and the insulating resin layer is a shape that gradually protrudes outward as it moves away from the insulating resin layer along the stacking direction, or a shape that extends in a direction perpendicular to the joint interface, and the distance W along the joint interface between the end face position at the joint interface of the circuit layer and the end face position at the center of the thickness of the circuit layer is within a range of 0 mm to 2 mm.

[0007] Patent Document 3 proposes a method for manufacturing an insulated circuit board including a metal substrate, an insulating resin layer mainly composed of a thermosetting resin formed on one side of the metal substrate, and a circuit layer having a circuit pattern formed on the side of the insulating resin layer opposite the metal substrate, wherein the circuit layer is made of a metal material and has a thickness in the range of 0.05 mm to 2.0 mm. The method includes a lamination step of arranging an insulating resin layer mainly composed of a cured thermosetting resin on one side of the metal substrate, a metal piece arranging step of arranging a plurality of metal pieces in a circuit pattern on the insulating resin layer and arranging pressing members in areas other than the metal pieces, and a metal piece joining step of pressing the metal substrate, the insulating resin layer, the metal pieces, and the pressing jig in the stacking direction while heating them, and wherein the metal substrate, the insulating resin layer, and the metal pieces are joined together, wherein the metal piece joining step involves heating to a temperature equal to or higher than the glass transition temperature of the thermosetting resin contained in the insulating resin layer. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 6-169147 [Patent Document 2] Japanese Patent Application Publication No. 2018-147934 [Patent Document 3] Japanese Patent Application Publication No. 2019-169540 Summary of the Invention [Problem to be solved by the invention]

[0009] However, it has been found that the metal base circuit boards manufactured by the methods of Patent Documents 1 to 3 have insufficient voltage resistance characteristics in the thickness direction.

[0010] Therefore, it is desired to provide a metal base circuit board with excellent voltage resistance characteristics.

[0011] SUMMARY OF THE INVENTION In view of the above-mentioned problems in the prior art, an object of the present invention is to provide a metal base circuit board with improved voltage resistance characteristics and a method for manufacturing the same. [Means for solving the problem]

[0012] A first aspect of the present invention is a first lamination step of placing a thermosetting resin sheet on a metal base plate and placing a first bonding spacer made of a rubber sheet including a reinforcing member on the thermosetting resin sheet; a first joining step of heating the metal base plate and the thermosetting resin sheet while applying pressure to each other in a stacking direction of the metal base plate and the thermosetting resin sheet via the first joining spacer to join the metal base plate and the thermosetting resin sheet together to obtain a first joined body; a second lamination step of placing a metal plate on a surface of the thermosetting resin sheet of the first bonded body, and placing a second bonding spacer made of a rubber sheet including a reinforcing member on the metal plate; and a second joining step of heating the metal plate and the first joining body while applying pressure via the second joining spacer in the stacking direction of the metal plate and the first joining body to join the metal plate and the first joining body.

[0013] A second aspect of the present invention is The first joint spacer and the second joint spacer are A layer of a reinforcing member made of glass cloth is formed inside the silicone rubber sheet or the fluororubber sheet. A method for producing the metal base circuit board according to the first aspect.

[0014] A third aspect of the present invention is In the first bonding step, a higher pressure is applied than in the second bonding step. A method for producing the metal base circuit board according to the first aspect.

[0015] A fourth aspect of the present invention is In the first joining step, a pressure of 10 MPa or more and 30 MPa or less is applied, In the second joining step, pressure is applied at a pressure of 1 MPa or more and 15 MPa or less. A method for producing the metal base circuit board according to the first aspect.

[0016] A fifth aspect of the present invention is In the second lamination step, a positioning jig having an opening with substantially the same outer dimensions as the metal plate is placed on the thermosetting resin sheet, and the metal plate is placed in the opening; A method for producing the metal base circuit board according to the first aspect.

[0017] A sixth aspect of the present invention is a method for manufacturing a semiconductor device comprising: The surface of the positioning jig is made of a material that does not bond to the thermosetting resin sheet during bonding. A method for producing the metal base circuit board according to the fifth aspect.

[0018] A seventh aspect of the present invention is After the metal plate and the first bonded body are bonded in the second bonding step, Further, a resin curing step of curing the thermosetting resin sheet by performing heat treatment is included. A method for producing the metal base circuit board according to the first aspect.

[0019] An eighth aspect of the present invention is In the resin curing step, After removing the pressure applied in the second bonding step, heat treatment is performed. A method for producing the metal base circuit board according to the seventh aspect.

[0020] A ninth aspect of the present invention is a method for manufacturing a semiconductor device comprising: The metal base plate is copper or a copper alloy. A method for producing the metal base circuit board according to the first aspect.

[0021] A tenth aspect of the present invention is a method for manufacturing a semiconductor device comprising: The metal plate is copper or a copper alloy. A method for producing the metal base circuit board according to the first aspect.

[0022] An eleventh aspect of the present invention is a method for manufacturing a semiconductor device comprising: the first bonding spacer and the second bonding spacer have a compression set of 20% or less under conditions of 180°C x 24 hours; A method for manufacturing a metal base circuit board according to any one of the first to tenth aspects.

[0023] A twelfth aspect of the present invention is a method for manufacturing a semiconductor device comprising: a metal plate is bonded to a metal base plate via an insulating resin layer, and the dimensional difference between the edge of the top surface and the edge of the bottom surface of the metal plate at the periphery of the metal plate is ±50 μm or less; When a voltage is applied between the metal base plate and the metal plate and the voltage is increased by 0.1 kV at a holding time of 5 seconds, the voltage V at the point when the leakage current reaches 1 mA is divided by the thickness t of the insulating resin layer, and the value V / t is 10 kV / mm or more.

[0024] A thirteenth aspect of the present invention is a method for manufacturing a semiconductor device comprising: The bonding rate between the metal plate and the metal base plate is 98% or more by area. The metal base circuit board according to the twelfth aspect.

[0025] A fourteenth aspect of the present invention is a method for manufacturing a semiconductor device comprising: The bonding strength between the metal plate and the metal base plate is 8 MPa or more. The metal base circuit board according to the twelfth aspect.

[0026] A fifteenth aspect of the present invention is a method for manufacturing a semiconductor device comprising: The metal base plate is copper or a copper alloy. The metal base circuit board according to the twelfth aspect.

[0027] A sixteenth aspect of the present invention is a method for manufacturing a semiconductor device comprising: The metal plate is copper or a copper alloy. The metal base circuit board according to the twelfth aspect.

[0028] A seventeenth aspect of the present invention is a method for manufacturing a semiconductor device comprising: The thickness of the metal plate is 0.4 mm or more. The metal base circuit board according to any one of the twelfth to sixteenth aspects. [Effects of the Invention]

[0029] The present invention can provide a metal base circuit board with improved voltage resistance characteristics and a method for manufacturing the same. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. 1 is a flowchart showing an example of a method for manufacturing a metal base circuit board according to an embodiment of the present invention. [Figure 2] Fig. 2(a) is a top view of a metal base circuit board according to an embodiment of the present invention, Fig. 2(b) is a cross-sectional view taken along line AA in Fig. 2(a), and Fig. 2(c) is a bottom view of Fig. 2(a). [Figure 3] FIG. 3 is a cross-sectional view showing a state in which a thermosetting resin sheet is placed on a metal base plate and a first bonding spacer is placed on the thermosetting resin sheet in the embodiment of the present invention. [Figure 4] FIG. 4 is a cross-sectional view showing a state in which a metal plate is placed on the surface of a thermosetting resin sheet of a first bonding body and a second bonding spacer is placed on the metal plate in the embodiment of the present invention. [Figure 5] Fig. 5(a) is a top view showing a state in which a metal plate and a positioning jig are placed on a thermosetting resin sheet and a second bonding spacer is placed on the metal plate in an embodiment of the present invention. Fig. 5(b) is a cross-sectional view taken along line BB of Fig. 5(a). Fig. 5(c) is a bottom view of Fig. 5(a). [Figure 6]Fig. 6(a) is a top view of another embodiment of the present invention, in which a metal plate and a positioning jig are placed on a thermosetting resin sheet, and a second joining spacer is placed on the metal plate via a joining jig. Fig. 6(b) is a cross-sectional view taken along the line B--B of Fig. 6(a). Fig. 6(c) is a bottom view of Fig. 6(a). [Figure 7] Fig. 7(a) is a top view of a metal base plate according to another embodiment of the present invention, with heat dissipation pins formed on the rear surface thereof, Fig. 7(b) is a cross-sectional view taken along CC in Fig. 7(a), and Fig. 7(c) is a bottom view of Fig. 7(a). [Figure 8] FIG. 8 is an enlarged side view of the peripheral edge of a metal plate when a circuit pattern is formed by etching. DETAILED DESCRIPTION OF THE INVENTION

[0031] [Details of the embodiment of the present invention] Next, embodiments of the present invention will be described below with reference to the drawings. Note that the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0032] In this specification, "A to B" means a numerical range of "A or more and B or less."

[0033] <Metal base circuit board manufacturing method> Fig. 1 is a flowchart showing an example of a method for manufacturing a metal base circuit board according to the present invention. As shown in Fig. 1, the method for manufacturing a metal base circuit board according to the present invention includes, for example, a first lamination step S1 in which a thermosetting resin sheet is placed on a metal base plate and a first bonding spacer made of a rubber sheet containing a reinforcing member is placed on the thermosetting resin sheet, a first bonding step S2 in which pressure is applied via the first bonding spacer in the lamination direction of the metal base plate and the thermosetting resin sheet, and heating is performed to bond the metal base plate and the thermosetting resin sheet together to obtain a first bonded body, a second lamination step S3 in which a metal plate is placed on the surface of the thermosetting resin sheet of the first bonded body, and a second bonding spacer made of a rubber sheet containing a reinforcing member is placed on the metal plate, and a second bonding step S4 in which pressure is applied via the second bonding spacer in the lamination direction of the metal plate and the first bonded body, and heating is performed to bond the metal plate and the first bonded body together. Furthermore, the method for manufacturing a metal base circuit board of the present invention preferably further comprises, after the second joining step S4, a resin curing step S5 in which the thermosetting resin sheet is cured by a heat treatment.

[0034] By the method for manufacturing a metal base circuit board of the present invention, a metal base circuit board with improved voltage resistance characteristics can be manufactured.

[0035] An embodiment of the method for manufacturing a metal base circuit board according to the present invention will be described with reference to the drawings. As shown in Figures 2(a) to 2(c), the metal base circuit board 1 of the present invention has a structure in which a metal plate 30 as a circuit pattern is bonded onto a metal base plate 10 via an insulating resin layer 21. Figure 2(a) is a top view of the metal base circuit board 1 as seen from above the metal plate 30, Figure 2(b) is a cross-sectional view taken along line AA in Figure 2(a), and Figure 2(c) is a bottom view.

[0036] (First lamination step S1) In the first lamination process S1, as shown in FIG. 3, a thermosetting resin sheet 20 is placed on a metal base plate 10, and a first joining spacer 2 consisting of a rubber sheet 100 including a reinforcing member 110 is placed on the thermosetting resin sheet 20.

[0037] (First joining step S2) Then, in the first bonding step S2, the metal base plate 10 and the thermosetting resin sheet 20 are heated while being pressed in the stacking direction of the metal base plate 10 and the thermosetting resin sheet 20 via a first bonding spacer 2, for example, using a hot press device, to bond the metal base plate 10 and the thermosetting resin sheet 20 together to obtain a first bonded body 3. The first bonded body 3 is an intermediate body for obtaining the final metal base circuit board 1.

[0038] The metal base plate 10 is, for example, a material that constitutes a metal base portion that functions as a heat sink in the metal base circuit board 1. The metal used for the metal base plate 10 is preferably copper or a copper alloy. The thickness of the metal base plate 10 that can be suitably used is 1.5 mm or more and 3.0 mm or less.

[0039] The thermosetting resin sheet 20 is, for example, a resin sheet containing a thermosetting resin, and serves as the material for the insulating resin layer 21. The thermosetting resin is preferably one or more selected from epoxy resin, polyurethane resin, and polyimide resin. The thermosetting resin sheet 20 preferably contains a ceramic filler to improve thermal conductivity. The ceramic filler is preferably one or more selected from boron nitride (BN), aluminum nitride (AlN), magnesium oxide (MgO), and aluminum oxide (Al2O3). The content of the ceramic filler is preferably such that the thermal conductivity of the thermosetting resin sheet 20 (insulating resin layer 21) is 8 W / (m·K) or more and 20 W / (m·K) or less. The thickness of the thermosetting resin sheet 20 is preferably 50 μm or more and 500 μm or less.

[0040] The first bonding spacer 2 is a sheet placed between the thermosetting resin sheet 20 and a press when the thermosetting resin sheet 20 is heated under pressure in the first bonding step S2. As shown in Fig. 3, the first bonding spacer 2 is preferably one in which both sides of a layer of reinforcing member 110 are covered with layers of rubber sheets 100, for example.

[0041] The reinforcing member 110 is, for example, a material placed inside the rubber sheet 100 to increase the mechanical strength of the rubber sheet 100, and glass fiber or carbon fiber can be suitably used. As the reinforcing member 110, a glass cloth (glass fiber fabric) made by weaving glass fiber can be suitably used.

[0042] For example, a silicone rubber sheet or a fluororubber sheet can be suitably used as the rubber sheet 100. Silicone rubber is particularly preferable because it is inexpensive and easy to procure. When using a silicone rubber sheet as the rubber sheet 100, it is preferable to use one with a hardness type A (see JIS K 6253) of 30 to 80 and a tensile strength of 5 to 15 MPa. Furthermore, when using a fluororubber sheet as the rubber sheet 100, it is preferable to use one with a hardness type A of 60 to 80.

[0043] The thickness of the first joint spacer 2 is preferably 0.5 to 2.0 mm, and more preferably 0.6 to 1.7 mm. The thickness of the layer of the reinforcing member 110 is preferably 1 / 4 to 1 / 2 the thickness of the first joint spacer 2, and it is preferable that layers of the rubber sheet 100 of approximately the same thickness are formed on both sides of the layer of the reinforcing member 110. Furthermore, from the viewpoint of efficiently suppressing deformation of the first joint spacer 2, the maximum elongation percentage of the reinforcing member 110 is preferably 10% or less. Furthermore, it is preferable that the compression set (see JIS K 6262) of the first bonding spacer 2 is small, and for example, it is preferably 20% or less under the conditions of 180°C x 24 hours.

[0044] In the first bonding step S2, the first bonding spacer 2 is used to apply pressure uniformly across the entire area of ​​the thermosetting resin sheet 20. This reduces the gap between the metal base plate 10 and the thermosetting resin sheet 20, making it possible to improve the pressure resistance of the metal base circuit board 1.

[0045] Furthermore, in the method for manufacturing a metal base circuit board of the present invention, the metal base plate 10, thermosetting resin sheet 20, and metal plate 30 are not bonded together at once, but in the first bonding step S2, only the metal base plate 10 and the thermosetting resin sheet 20 are bonded together. This makes it easier to reduce the gap between the metal base plate 10 and the thermosetting resin sheet 20, and enables the pressure resistance characteristics of the metal base circuit board 1 to be improved.

[0046] In the first bonding step S2, it is preferable to apply pressure higher than in the second bonding step S4 described below, and it is also preferable to heat at a temperature lower than in the second bonding step S4. Specifically, in the first bonding step S2, it is preferable to apply pressure at a pressure of 10 MPa or more and 30 MPa or less, and it is also preferable to heat at a temperature of 80°C or more and 140°C or less. This allows the thermosetting resin sheet 20 to be pressurized sufficiently and uniformly without being completely cured, making it easier to reduce the gap between the metal base plate 10 and the thermosetting resin sheet 20.

[0047] In the first bonding step S2, a protective sheet or the like may be placed between the thermosetting resin sheet 20 and the first bonding spacer 2 to prevent the thermosetting resin sheet 20 and the first bonding spacer 2 from adhering to each other, and a metal spacer or the like may be placed between the first bonding spacer 2 and the pressing means to prevent the first bonding spacer 2 from adhering to the pressing means. When a metal spacer is placed between the first bonding spacer 2 and the pressing means, the material of the metal spacer is preferably aluminum, and the thickness of the metal spacer is preferably 0.1 mm to 5 mm, and more preferably 1 mm to 5 mm. Furthermore, in order to further improve the pressure resistance characteristics of the resulting metal base circuit board 1, in the first joining step S2, it is preferable to place the metal base plate 10, the thermosetting resin sheet 20 and the first joining spacer 2 on a metal plate, and the metal plate is preferably an aluminum plate.

[0048] (Second lamination step S3) In the second lamination step S3, as shown in FIG. 4, a metal plate 30 is placed on the surface of the thermosetting resin sheet 20 of the first bonding body 3, and a second bonding spacer 4 made of a rubber sheet 100 including a reinforcing member 110 is placed on the metal plate 30.

[0049] (Second joining step S4) Then, in the second bonding step S4, the metal plate 30 and the first bonding body 3 are heated while being pressed in the stacking direction of the metal plate 30 and the first bonding body 3 via the second bonding spacer 4 using, for example, a hot press device, to bond the metal plate 30 and the first bonding body 3 to obtain the second bonding body 5. The thermosetting resin sheet 20 of the second bonding body 5 is cured to form the insulating resin layer 21, and the final metal base circuit board 1 can be obtained.

[0050] The metal plate 30 is a material that constitutes the circuit in the metal base circuit board 1. The metal used for the metal plate 30 is preferably copper or a copper alloy. The thickness of the metal plate 30 that can be used is preferably 0.4 mm or more and 2.0 mm or less.

[0051] The second joining spacer 4 is a sheet that is placed between the metal plate 30 and a press when the metal plate 30 is heated under pressure in the second joining step S4. As shown in Fig. 4, the second joining spacer 4 is preferably one in which, for example, both sides of a layer of reinforcing member 110 are covered with layers of rubber sheets 100.

[0052] The second junction spacer 4 may be the same as or different from the first junction spacer 2. The preferred materials and characteristic values ​​for the second junction spacer 4 are the same as those described for the first junction spacer 2.

[0053] The second bonding spacer 4 is preferably formed such that the member on the side that comes into contact with the metal plate 30 is made of a relatively soft plate (sheet) material (for example, a silicone rubber sheet) that deforms appropriately. This allows the layer of rubber sheet 100 on the surface of the second bonding spacer 4 to conform to the surface of the metal plate 30 so as to adhere closely to it, even if the metal plate 30 is warped or wavy, or if the metal plate 30 is placed on the thermosetting resin sheet 20 in an inclined state during lamination. Furthermore, when pressure is applied in the stacking direction to bond the sheets, the layer of glass cloth reinforcing member 110 formed inside the second bonding spacer 4 suppresses deformation of the second bonding spacer 4, and uniformly applies load (pressure) to the surface of the metal plate 30, thereby suppressing the occurrence of bonding defects. In addition, the second joining spacer 4 has the component on the opposite side (the side that comes into contact with a press, etc.) to the side that comes into contact with the metal plate 30 also formed from the rubber sheet 100, thereby improving heat transfer and pressure uniformity during joining.

[0054] In the second bonding step S4, by using the second bonding spacer 4, it is possible to apply pressure uniformly over the entire area of ​​the metal plate 30. This reduces the gap between the metal plate 30 and the thermosetting resin sheet 20, and improves the pressure resistance characteristics of the metal base circuit board 1.

[0055] Furthermore, as described above, in the method for manufacturing a metal base circuit board of the present invention, the metal base plate 10, thermosetting resin sheet 20, and metal plate 30 are not bonded all at once, but are bonded in two stages. This makes it easier to reduce the gap between the metal plate 30 and the thermosetting resin sheet 20, and enables the pressure resistance characteristics of the metal base circuit board 1 to be improved.

[0056] In the second bonding step S4, it is preferable to apply pressure of, for example, 1 MPa or more and 15 MPa or less, and to heat at a temperature of 150° C. or more and 210° C. or less, which makes it possible to obtain good bonding strength.

[0057] In the second bonding step S4, a metal spacer or the like may be placed between the second bonding spacer 4 and the pressing means in order to prevent the second bonding spacer 4 and the pressing means from adhering to each other. In order to further improve the voltage resistance characteristics of the resulting metal base circuit board 1, it is preferable to place the first bonding body 3, the metal plate 30 and the second bonding spacer 4 on a metal plate in the second bonding step S4, and the metal plate is preferably an aluminum plate.

[0058] It has been found that in the second bonding step S4, if a metal plate such as an aluminum plate or a stainless steel plate is placed on the metal plate as a spacer without using the second bonding spacer 4, and then the metal plate is pressed and bonded to produce a metal base circuit board, many bonding defects (voids) occur at the bonding interface between the metal plate and the metal base plate. Furthermore, it was found that in the second bonding step S4, even when the second bonding spacer 4 is not used, and for example, a rubber sheet containing no reinforcing member is placed on the metal plate as a spacer, and then the metal plate is pressed and bonded to produce a metal base circuit board, many bonding defects (voids) occur at the bonding interface between the metal plate and the metal base plate. In contrast, by using the second bonding spacer 4 in the second bonding step S4, it is possible to suppress the occurrence of bonding defects.

[0059] FIG. 5(a) is a top view of the second bonding spacer 4, as viewed from above, with a metal plate 30 and a positioning jig 200 placed on the thermosetting resin sheet 20, and a second bonding spacer 4 placed on the metal plate 30. FIG. 5(b) is a cross-sectional view taken along the line B-B of FIG. 5(a), and FIG. 5(c) is a bottom view. As shown in FIGS. 5(a) to 5(c), in the second lamination step S3, a positioning jig 200 made of, for example, a metal plate or a heat-resistant resin plate such as Teflon (registered trademark) and having an opening with approximately the same external dimensions as the metal plate 30 is preferably placed on the thermosetting resin sheet 20, and the metal plate 30 is placed in the opening to position the metal plate 30 as a circuit pattern in a predetermined position. Furthermore, the surface of the positioning jig 200 is preferably made of a material that will not bond to the thermosetting resin sheet 20 during thermal bonding. Specifically, it is preferable that the base material of the positioning jig 200 is a metal plate such as stainless steel (SUS), and that the surface thereof is coated with, for example, Teflon (registered trademark) or silicone rubber. It is also preferable to use Teflon (registered trademark) as the material of the positioning jig 200, which does not bond to the thermosetting resin sheet 20.

[0060] By placing a metal plate 30 having a predetermined circuit pattern shape in the opening of such a positioning jig 200 and bonding it, the predetermined circuit pattern is formed on the metal base plate 10 via the thermosetting resin sheet 20 (insulating resin layer 21), resulting in a finished product after bonding. Bonding using such a positioning jig 200 is preferable because it eliminates the need for a circuit formation process such as etching the metal plate 30. This is particularly preferable when the metal plate 30 is thick (for example, when the thickness is 1 mm or more), as it is difficult to ensure dimensional accuracy by etching.

[0061] Moreover, Figure 6(a) is a top view of the second joining spacer 4 seen from above when a metal plate 30 and a positioning jig 200 are placed on a thermosetting resin sheet 20, and the second joining spacer 4 is placed on the metal plate 30 via a joining jig 300 made of a metal plate, Figure 6(b) is a BB cross-sectional view of Figure 6(a), and Figure 6(c) is a bottom view.

[0062] As shown in FIGS. 6(a) to 6(c), in the second lamination step S3, a positioning jig 200 having an opening with approximately the same outer dimensions as the metal plate 30 is placed on the thermosetting resin sheet 20, the metal plate 30 is placed in the opening, and the metal plate 30 as a circuit pattern is positioned in a predetermined position. When placing the second bonding spacers 4 on each metal plate 30, the bonding jig 300 made of a metal plate may be placed between the metal plate 30 and the second bonding spacers 4, and then the second bonding spacers 4 may be placed on top of the metal plate 30. Using the bonding jig 300 facilitates stable bonding regardless of whether the metal plate 30 is thin or thick. Furthermore, deformation of the positioning jig 200 is suppressed, allowing the positioning jig 200 to be used repeatedly for a long period of time. Note that when the metal plate 30 is particularly thin, the positioning jig 200 is also thin and particularly prone to deformation, so it is preferable to use only the bonding jig 300 without using the positioning jig 200.

[0063] (Resin curing process S5) In the resin curing step S5, after the metal plate 30 and the first bonding body 3 are bonded in the second bonding step S4, the pressure applied in the second bonding step S4 is removed, and further heat treatment is performed to harden the thermosetting resin sheet 20 (to form the insulating resin layer 21).

[0064] In the resin curing step S5, it is preferable to perform heat treatment in nitrogen gas at a temperature of 150° C. or higher and 210° C. or lower, for example, so that good bonding strength can be obtained.

[0065] Through the above steps, the metal base circuit board 1 of the present invention can be produced.

[0066] In another embodiment of the present invention, a method for manufacturing a metal base circuit board can be provided, for example, including a lamination step of placing a thermosetting resin sheet on a metal base plate, placing a metal plate on the thermosetting resin sheet, and placing a bonding spacer made of a rubber sheet containing a reinforcing member on the metal plate; and a bonding step of heating the metal base plate, thermosetting resin sheet, and metal plate while applying pressure via the bonding spacer in the lamination direction of the metal base plate, thermosetting resin sheet, and metal plate to bond the metal base plate, resin sheet, and metal plate. In this way, even when bonding is performed in one step, using a bonding spacer made of a rubber sheet containing a reinforcing member can produce a metal base circuit board with fewer bonding defects. Furthermore, the process can be simplified compared to the above embodiment. However, from the perspective of improving pressure resistance, bonding in two steps as in the above embodiment is preferable.

[0067] <Metal-based circuit board> The metal base circuit board 1 of the present invention is characterized in that a metal plate 30 is joined onto a metal base plate 10 via an insulating resin layer 21, and that at the peripheral portion of the metal plate 30, the dimensional difference between the edge of the top surface and the edge of the bottom surface of the metal plate 30 is ±50 μm or less, and when a voltage is applied between the metal base plate 10 and the metal plate 30 and the voltage is increased in 0.1 kV increments with a holding time of 5 seconds, the value V / t obtained by dividing the voltage V at the time when the leakage current reaches 1 mA by the thickness t of the insulating resin layer 21 is 10 kV / mm or more.

[0068] Furthermore, in the metal base circuit board 1 of the present invention, it is preferable that the bonding rate between the metal plate 30 and the metal base plate 10 is 98 area % or more, it is preferable that the bonding strength between the metal plate 30 and the metal base plate 10 is 8 MPa or more, it is preferable that the metal base plate 10 is copper or a copper alloy, it is preferable that the metal plate 30 is copper or a copper alloy, and it is preferable that the thickness of the metal plate 30 is 0.4 mm or more.

[0069] Fig. 8 is an enlarged side view of the peripheral portion of the metal plate 30 when a circuit pattern is formed by etching. As shown in Fig. 8, when a circuit pattern is formed by etching, the dimensional difference w between the end of the top surface and the end of the bottom surface of the metal plate 30 may become large at the peripheral portion of the metal plate 30 (hereinafter also referred to as skirt length w). In contrast, the metal base circuit board 1 of the present invention is not etched, and therefore has a small skirt length w (±50 µm or less). In this specification, the skirt length w is considered positive (+) when the dimension of the end of the bottom surface of the metal plate 30 is larger than the dimension of the end of the top surface, and is considered negative (-) when the dimension of the end of the bottom surface is smaller than the dimension of the end of the top surface.

[0070] Furthermore, in the metal base circuit board 1 of the present invention, the absolute value (T / w) of the thickness T of the metal plate 30 divided by the skirt length w is preferably greater than 4 (more preferably 10 or more, and even more preferably 50 or more). In other words, the metal base circuit board 1 of the present invention has excellent dimensional accuracy because the circuit pattern is formed by punching without etching. Furthermore, even though bonding is performed after punching the circuit pattern, a high bonding rate and bonding strength are achieved by the ingenuity of the manufacturing method described above. The dimensional difference w (skirt length w) can be measured by observing a cross section perpendicular to the edge (periphery, periphery) of the circuit of the metal plate 30 when the metal plate 30 for the circuit of the metal base circuit board 1 is viewed from above.

[0071] An embodiment of a metal base circuit board of the present invention will be described with reference to Figures 1(a) to 1(c). In an embodiment of a metal base circuit board 1 of the present invention, one surface of an insulating resin layer 21 is bonded to the surface (one plate surface) of a metal base plate 10, and (one plate surface of) a metal plate 30 is bonded to the other surface of the insulating resin layer 21. That is, the metal plate 30 is bonded to the metal base plate 10 via the insulating resin layer 21, and the insulating resin layer 21 ensures insulation between the two and also serves as a bonding material for bonding them together. Furthermore, by devising the above-mentioned manufacturing method, the gap between the metal base plate 10 and the insulating resin layer 21 and the gap between the metal plate 30 and the insulating resin layer 21 are reduced, making it possible to provide a metal base circuit board 1 with excellent voltage resistance characteristics.

[0072] Furthermore, when the bonding interface between the metal plate 30 and the metal base plate 10 of the metal base circuit board 1 is observed with an ultrasonic flaw detector, the bonding rate of one plate surface (bonding surface) of the metal plate 30 is 98 area % or more, and it can be said that the metal base circuit board 1 has few bonding defects and is a highly reliable board.

[0073] The metal plate 30 constitutes the circuit pattern of the metal base circuit board 1 and is preferably made of copper (Cu) or a copper alloy (Cu alloy). The metal base plate 10 is used as a heat sink and is preferably made of copper (Cu) or a copper alloy (Cu alloy) with high heat dissipation properties. The thickness of the metal plate 30 is preferably 0.4 mm or more, more preferably 0.8 mm or more, and even more preferably 1.0 mm or more, and is preferably 2.0 mm or less. The thickness of the metal base plate 10 is preferably 1.5 to 3.0 mm.

[0074] Fig. 7(a) is a top view of a metal base plate 10 according to another embodiment of the present invention, having heat dissipation pins 11 formed on the back surface thereof. Fig. 7(b) is a cross-sectional view taken along CC in Fig. 7(a), and Fig. 7(c) is a bottom view of Fig. 7(a). As shown in Figs. 7(a) to 7(c), the metal base plate 10 may be provided with heat dissipation pins 11 (or fins) on the surface opposite to the surface to which the thermosetting resin sheet 20 is bonded. This can further improve the heat dissipation characteristics. [Example]

[0075] Next, examples of the present invention will be described. These examples are merely examples of the present invention, and the present invention is not limited to these examples.

[0076] [Example 1] A rectangular oxygen-free copper (C1020) sheet measuring 85 mm in length, 85 mm in width, and 2 mm in thickness was prepared as the material for the metal base plate. Four rectangular oxygen-free copper (C1020) sheets measuring 38 mm in length, 38 mm in width, and 1.2 mm in thickness were prepared as the material for the metal circuit board (metal plate). A rectangular thermosetting resin sheet measuring 85 mm in length, 85 mm in width, and 150 μm in thickness, composed of polyimide resin and ceramic filler, was prepared as the material for the insulating resin layer.

[0077] (First lamination process) The protective sheets on both sides of the thermosetting resin sheet were peeled off from only one side, and the thermosetting resin sheet was placed on a metal base plate with the remaining protective sheet facing up. A 1.5 mm thick first bonding spacer (Maxell Kureha Co., Ltd., glass cloth-reinforced silicone rubber sheet, product number SR970P) made of a composite material of silicone rubber and glass cloth layers, with the glass cloth layer formed in the center of the thickness direction of the silicone rubber plate, was placed on top of the thermosetting resin sheet. The compression set of the first bonding spacer was 14% under conditions of 180°C x 24 hours, and the hardness type A of the silicone rubber sheet of the first bonding spacer was 70.

[0078] (First joining process) The metal base plate, thermosetting resin sheet, and first bonding spacer were placed in a hot press, and an aluminum plate (0.3 mm thick) was placed on top of the first bonding spacer as a metal spacer. Under a reduced pressure of approximately 100 Pa, the first bonding spacer was pressurized at 20 MPa through the metal spacer, and the mixture was heated at 110°C for 5 minutes, and then cooled to obtain a first bonded body in which the metal base plate and thermosetting resin sheet were bonded.

[0079] (Second lamination process) After peeling off the protective sheet remaining on the surface of the thermosetting resin sheet, four metal circuit plates were placed on top of it using a positioning jig. As shown in Figure 5(a), the positioning jig was a 1.0 mm thick stainless steel plate with openings of approximately the same shape as the four metal circuit plates, so that the four metal circuit plates were arranged in a square pattern with a 1 mm spacing between the patterns (the distance between the edges of adjacent metal circuit plates). The plate surface (front surface) was coated with Teflon (registered trademark), which had approximately the same thickness as the metal circuit plates. A second bonding spacer (glass cloth-reinforced silicone rubber sheet, product number SR970P, manufactured by Maxell Kureha Co., Ltd.) was then placed on top of the metal circuit plates.

[0080] (Second joining process) The first bonded body, metal circuit board, second bonding spacer, and positioning jig were placed on an aluminum plate (1 mm thick) placed in a hot press, and an aluminum plate (3 mm thick) was placed on the bonding spacer as a metal spacer.The assembly was heated at 180°C for 10 minutes in the atmosphere while applying a pressure of 7 MPa from above the second bonding spacer via the metal spacer, and then cooled to obtain a second bonded body in which the metal base plate and metal circuit board were bonded via a thermosetting resin sheet.

[0081] (Resin curing process) The second bonded body was heated in nitrogen gas without pressure at 180° C. for 2 hours to harden the thermosetting resin sheet, thereby forming an insulating resin layer, and a metal base circuit board was produced.

[0082] (Voltage resistance characteristic evaluation) The withstand voltage characteristics of the metal base circuit board were evaluated using a withstand voltage tester (manufactured by Hioki E.E. Corporation). Specifically, the metal base circuit board was placed on a copper plate, a probe was contacted to the metal circuit board, and the voltage was increased in 0.1 kV increments with a holding time of 5 seconds. The voltage V at the point when the leakage current reached 1 mA was divided by the thickness t of the insulating resin layer to evaluate the withstand voltage characteristics, V / t (kV / mm). The resulting V / t was 16.3 kV / mm.

[0083] (bonding rate evaluation) For metal base circuit boards, an ultrasonic flaw detector (SAT) (FS100II, manufactured by Hitachi Construction Machinery FineTech Co., Ltd.) was used to obtain ultrasonic flaw images of the joint between the metal base plate and the metal circuit plate, and the image was then binarized using an application attached to the SAT to calculate the area of ​​the joined region (not the unjoined region), and the ratio of the area of ​​the joined region to the area of ​​the entire joint (the area where the metal circuit plate was placed) was determined, and this ratio was taken as the bonding rate. As a result, the bonding rate was over 98% area, indicating good bonding.

[0084] [Example 2] A metal base circuit board was produced in the same manner as in Example 1, except that in the first bonding step, an aluminum plate (thickness: 3 mm) was further placed on the first bonding spacer as a metal spacer.

[0085] The resulting metal base circuit board was evaluated for voltage resistance and bonding rate in the same manner as in Example 1, and the V / t was found to be 15.7 kV / mm. The bonding rate was 98 area % or more, indicating good bonding.

[0086] [Example 3] A metal base circuit board was produced in the same manner as in Example 1, except that in the first bonding step, the metal base plate, the thermosetting resin sheet, and the first bonding spacer were placed on an aluminum plate (thickness 1 mm) placed in a hot press.

[0087] The resulting metal base circuit board was evaluated for voltage resistance and bonding rate in the same manner as in Example 1, and the V / t was found to be 17.1 kV / mm. The bonding rate was 98 area % or more, indicating good bonding.

[0088] [Example 4] In the first bonding step, the metal base plate, the thermosetting resin sheet, and the first bonding spacer were placed on an aluminum plate (thickness 1 mm) placed in a hot press, and a metal base circuit board was produced in the same manner as in Example 1, except that an aluminum plate (thickness 3 mm) was further placed on the first bonding spacer as a metal spacer.

[0089] The resulting metal base circuit board was evaluated for voltage resistance and bonding rate in the same manner as in Example 1, and the V / t was found to be 21.7 kV / mm. The bonding rate was 98 area % or more, indicating good bonding.

[0090] [Comparative Example 1] A metal base circuit board was produced in the same manner as in Example 1, except that in the first lamination step, a first bonding spacer was not used, and in the first bonding step, the metal base plate and the thermosetting resin sheet were placed in a hot press, an aluminum plate (0.3 mm thick) was placed on the thermosetting resin sheet as a metal spacer, and the mixture was heated at 110°C for 5 minutes under a reduced pressure of approximately 100 Pa while applying a pressure of 20 MPa from above the metal spacer, and then cooled to obtain a first bonded body in which the metal base plate and the thermosetting resin sheet were bonded.

[0091] The resulting metal base circuit board was evaluated for voltage resistance and bonding rate in the same manner as in Example 1, and the V / t was found to be 8.60 kV / mm. The bonding rate was 98 area % or more, indicating good bonding.

[0092] From the above, it was confirmed that by performing bonding in two stages and using bonding spacers (first bonding spacer, second bonding spacer) during each bonding step, it is possible to manufacture metal base circuit boards with improved voltage resistance characteristics, with a V / t of 10 kV / mm or more.It was also confirmed that it is possible to manufacture metal base circuit boards with a bonding rate of 98 area % or more and few bonding defects. [Explanation of symbols]

[0093] 1 Metal-based circuit board 2 First joint spacer 3 First zygote 4 Second joint spacer 5 Second zygote 10 Metal base plate 11-pin 20 Resin sheet 21 insulating resin layer 30 metal plate 100 rubber sheets 110 Reinforcement member 200 Positioning jig 300 Joining jig S1 First lamination process S2 First joining process S3 Second lamination process S4 Second joining process S5 Resin curing process

Claims

1. a first lamination step of placing a thermosetting resin sheet on a metal base plate and placing a first joining spacer made of a rubber sheet including a reinforcing member on the thermosetting resin sheet; a first joining step of heating the metal base plate and the thermosetting resin sheet while applying pressure to each other in a stacking direction of the metal base plate and the thermosetting resin sheet via the first joining spacer to join the metal base plate and the thermosetting resin sheet together to obtain a first joined body; a second lamination step of placing a metal plate on a surface of the thermosetting resin sheet of the first bonded body, and placing a second bonding spacer made of a rubber sheet including a reinforcing member on the metal plate; a second joining step of heating the metal plate and the first joining body while applying pressure via the second joining spacer in the stacking direction of the metal plate and the first joining body to join the metal plate and the first joining body.

2. The first joint spacer and the second joint spacer are A layer of a reinforcing member made of glass cloth is formed inside the silicone rubber sheet or the fluororubber sheet. The method for manufacturing a metal base circuit board according to claim 1.

3. 2. The method for manufacturing a metal base circuit board according to claim 1, wherein a higher pressure is applied in said first bonding step than in said second bonding step.

4. In the first joining step, a pressure of 10 MPa or more and 30 MPa or less is applied, 2. The method for manufacturing a metal base circuit board according to claim 1, wherein the second bonding step applies pressure of 1 MPa or more and 15 MPa or less.

5. In the second lamination step, a positioning jig having an opening with substantially the same outer dimensions as the metal plate is placed on the thermosetting resin sheet, and the metal plate is placed in the opening; The method for manufacturing a metal-based circuit board according to claim 1 .

6. The surface of the positioning jig is made of a material that does not bond to the thermosetting resin sheet during bonding. The method for manufacturing a metal base circuit board according to claim 5.

7. After the metal plate and the first joined body are joined in the second joining step, Further, a resin curing step of curing the thermosetting resin sheet by performing heat treatment is included. The method for manufacturing a metal base circuit board according to claim 1.

8. In the resin curing step, After removing the pressure applied in the second bonding step, a heat treatment is performed. The method for manufacturing a metal base circuit board according to claim 7.

9. The metal base plate is copper or a copper alloy. The method for manufacturing a metal base circuit board according to claim 1.

10. The metal plate is copper or a copper alloy. The method for manufacturing a metal base circuit board according to claim 1.

11. the first bonding spacer and the second bonding spacer have a compression set of 20% or less under conditions of 180°C x 24 hours; The method for manufacturing a metal base circuit board according to any one of claims 1 to 10.

12. a metal plate is bonded to a metal base plate via an insulating resin layer, and a dimensional difference between an end of a top surface and an end of a bottom surface of the metal plate at a peripheral portion of the metal plate is ±50 μm or less; A metal base circuit board in which, when a voltage is applied between the metal base plate and the metal plate and the voltage is increased in increments of 0.1 kV with a holding time of 5 seconds, the value V / t obtained by dividing the voltage V at the time when the leakage current reaches 1 mA by the thickness t of the insulating resin layer is 10 kV / mm or more.

13. The bonding rate between the metal plate and the metal base plate is 98% or more by area.

13. The metal-based circuit board of claim 12.

14. The bonding strength between the metal plate and the metal base plate is 8 MPa or more.

13. The metal-based circuit board of claim 12.

15. The metal base plate is copper or a copper alloy.

13. The metal-based circuit board of claim 12.

16. The metal plate is copper or a copper alloy.

13. The metal-based circuit board of claim 12.

17. The thickness of the metal plate is 0.4 mm or more.

17. The metal base circuit board according to any one of claims 12 to 16.

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