Manufacturing method for insulating circuit boards

Abstract

To provide a manufacturing method of an insulation circuit board which stably prints a bonding paste on a first surface and a second surface of a ceramic board and stably manufactures the insulation circuit board.SOLUTION: A method includes a bonding paste printing step of printing a bonding paste on a first surface and a second surface of a ceramic board 11. The method also includes printing the bonding paste on the first surface of the ceramic board, inverting the ceramic board, placing the board on a printing stage 50 in which there is a recess part 52 on a mounting surface, and printing the bonding paste 25 on the second surface of the ceramic board in such a state that the bonding paste 25 printed on the first surface is stored in the recess part and the ceramic board is fixed by a suction part 55.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] This invention relates to a method for manufacturing an insulating circuit board including a ceramic substrate, a circuit layer formed on one surface of the ceramic substrate, and a metal layer formed on the other surface of the ceramic substrate.

Background Art

[0002] In power modules, LED modules, and thermoelectric modules, a structure is adopted in which power semiconductor elements, LED elements, and thermoelectric elements are joined to an insulating circuit board having a circuit layer made of a conductive material formed on one surface of a ceramic substrate. In addition, in the above-mentioned insulating circuit board, there is provided a structure in which a metal piece with excellent conductivity is joined to one surface of a ceramic substrate to form a circuit layer, and a metal piece with excellent heat dissipation is joined to the other surface of the ceramic substrate to form a metal layer. Furthermore, in order to efficiently dissipate heat generated in elements mounted on the circuit layer, etc., an insulating circuit board with a heat sink having a heat sink joined to the other surface side of the ceramic substrate is also provided.

[0003] For example, Patent Document 1 proposes an insulating circuit board in which a circuit layer and a metal layer are formed by joining copper plates to one surface and the other surface of a ceramic substrate. In this Patent Document 1, copper plates are arranged on one surface and the other surface of a ceramic substrate with an Ag-Cu-Ti-based brazing material interposed therebetween, and the copper plates are joined by performing a heat treatment (so-called active metal brazing method). <00​​​​

[0005] Furthermore, Patent Document 4 discloses an insulating circuit board in which a circuit layer made of an aluminum plate is formed on one side of a ceramic substrate and a metal layer made of an aluminum plate is formed on the other side. In this case, an Al-Si-based brazing material is used when joining the ceramic substrate to the aluminum plates that form the circuit layer and the metal layer. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 3211856 [Patent Document 2] Patent No. 5757359 [Patent Document 3] Japanese Patent Publication No. 2018-008869 [Patent Document 4] Patent No. 3171234 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] By the way, when forming a circuit layer on one side of a ceramic substrate and a metal layer on the other side of the ceramic substrate, it is necessary to print bonding paste on both sides of the ceramic substrate. The ceramic substrate is placed on the printing stage, and bonding paste is printed on one side of the ceramic substrate. Then, the ceramic substrate is flipped over and placed on the printing stage, and bonding paste is printed on the other side of the ceramic substrate.

[0008] As a result, the initially printed bonding paste would come into contact with the printing stage, and the pressure during printing would press the bonding paste against the printing stage, potentially causing the bonding paste to peel off or transferring dirt from the printing stage to the bonding paste. In particular, when an adhesive bonding paste was printed, the printed ceramic substrate could become firmly attached to the printing stage, making it difficult to remove.

[0009] This invention has been made in view of the circumstances described above, and aims to provide a method for manufacturing an insulating circuit board that can stably print bonding paste onto the first and second surfaces of a ceramic substrate, and can stably manufacture an insulating circuit board. [Means for solving the problem]

[0010] To solve the above-mentioned problems, an embodiment 1 of the present invention is a method for manufacturing an insulating circuit board comprising a ceramic substrate and a circuit layer and a metal layer formed by bonding metal pieces to a first surface and a second surface of the ceramic substrate, respectively, comprising: a bonding paste printing step of printing bonding paste to the first surface and the second surface of the ceramic substrate, respectively; a lamination step of laminating the ceramic substrate and the metal pieces that will become the circuit layer via the bonding paste, and laminating the ceramic substrate and the metal pieces that will become the metal layer via the bonding paste; and a bonding step of heat-treating the laminated metal pieces and the ceramic substrate to bond the metal pieces and the ceramic substrate, wherein the bonding In the bonding paste printing process, the bonding paste is printed on the first surface of the ceramic substrate, then the ceramic substrate is inverted and placed on a printing stage having a recess on its mounting surface, and the bonding paste is printed on the second surface of the ceramic substrate. The printing stage has a support portion formed on the periphery of the recess to support the end of the ceramic substrate, and a suction portion formed on the bottom side of the recess. When the inverted ceramic substrate is placed on the stage, the bonding paste printed on the first surface is contained within the recess, and the bonding paste is printed on the second surface of the ceramic substrate while the ceramic substrate is fixed in place by the suction portion.

[0011] According to the method for manufacturing an insulating circuit board of Embodiment 1 of the present invention, in the bonding paste printing step in which bonding paste is printed on a first surface and a second surface of a ceramic substrate, the bonding paste is printed on the first surface of the ceramic substrate, and then the inverted ceramic substrate is placed on a printing stage having a recess formed on the mounting surface, and the bonding paste printed on the first surface is contained in the recess and the ceramic substrate is fixed by a suction unit, and the bonding paste is then printed on the second surface of the ceramic substrate. As a result, when the bonding paste is printed on the second surface of the ceramic substrate, contact between the bonding paste printed on the first surface and the printing stage is suppressed, and the bonding paste can be stably printed on the first and second surfaces of the ceramic substrate. Furthermore, since the ceramic substrate is fixed by a suction unit, the bonding paste can be printed on the second surface of the ceramic substrate with high precision.

[0012] A method for manufacturing an insulating circuit board according to aspect 2 of the present invention is characterized in that, in the method for manufacturing an insulating circuit board according to aspect 1 of the present invention, the bonding paste is printed on the first surface of the ceramic substrate, the printed bonding paste is dried, and then the bonding paste is printed on the second surface of the ceramic substrate. According to the method for manufacturing an insulating circuit board of embodiment 2 of the present invention, even if the bonding paste printed on the first surface of the ceramic substrate and dried is tacky, when printing the bonding paste on the second surface of the ceramic substrate, contact of the dried bonding paste with the printing stage is suppressed, and the bonding paste can be stably printed on both the first and second surfaces of the ceramic substrate.

[0013] A third embodiment of the present invention is a method for manufacturing an insulating circuit board, characterized in that, in the method for manufacturing an insulating circuit board according to the first or second embodiment of the present invention, the ceramic substrate has scribe lines formed on it, and the recess is provided with ribs at positions corresponding to the scribe lines on the placed ceramic substrate. According to the method for manufacturing an insulating circuit board of embodiment 3 of the present invention, since scribe lines are formed on the ceramic substrate, multiple insulating circuit boards can be efficiently manufactured by printing bonding paste on the first and second surfaces of the ceramic substrate and then dividing the ceramic substrate along the scribe lines. Furthermore, since ribs are provided in the recess at positions corresponding to the scribe lines on the placed ceramic substrate, even large ceramic substrates can have their deflection suppressed during suction fixing and printing, and the bonding paste can be printed stably.

[0014] A method for manufacturing an insulating circuit board according to aspect 4 of the present invention is a method for manufacturing an insulating circuit board according to any one of aspects 1 to 3 of the present invention, characterized in that the bonding paste contains metal powder, an acrylic resin, a plasticizer consisting of an adipic acid ester, and a solvent, wherein the content of the plasticizer is in the range of 3.2 mass% to 10.4 mass%, and the ratio A / B of the weight A of the plasticizer to the weight B of the acrylic resin is in the range of 0.2 ≤ A / B ≤ 1.3. According to the method for manufacturing an insulating circuit board of embodiment 4 of the present invention, the bonding paste contains an acrylic resin and a plasticizer made of an adipic acid ester, the content of the plasticizer is in the range of 3.2 mass% to 10.4 mass%, and the ratio A / B of the weight A of the plasticizer to the weight B of the acrylic resin is in the range of 0.2 ≤ A / B ≤ 1.3, so that it has sufficient adhesive strength, and the bonding paste can be stably printed on the first and second surfaces of the ceramic substrate. [Effects of the Invention]

[0015] According to the present invention, a method for manufacturing an insulating circuit board is available that allows for stable printing of bonding paste onto the first and second surfaces of a ceramic substrate, and enables the stable production of an insulating circuit board. [Brief explanation of the drawing]

[0016] [Figure 1] Cross-sectional explanatory view of a power module using an insulating circuit board manufactured by the method for manufacturing an insulating circuit board according to an embodiment of the present invention. [Figure 2] Flow chart showing the method for manufacturing an insulating circuit board according to an embodiment of the present invention. [Figure 3] Explanatory view showing the method for manufacturing an insulating circuit board according to an embodiment of the present invention. [Figure 4] Explanatory view showing the paste printing process for bonding in the method for manufacturing an insulating circuit board according to an embodiment of the present invention. [Figure 5] Schematic explanatory view of a printing stage used in the paste printing process for bonding.

Mode for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0018] FIG. 1 shows an insulating circuit board 10 manufactured by the method for manufacturing an insulating circuit board according to an embodiment of the present invention, and a power module 1 using this insulating circuit board 10.

[0019] This power module 1 includes an insulating circuit board 10, a semiconductor element 3 joined via a solder layer 2 to one side (the upper side in FIG. 1) of the insulating circuit board 10, and a heat sink 31 disposed on the other side (the lower side in FIG. 1) of the insulating circuit board 10.

[0020] The solder layer 2 is made of, for example, a solder material such as Sn-Ag-based, Sn-Cu-based, Sn-In-based, or Sn-Ag-Cu-based (so-called lead-free solder material). The semiconductor element 3 is an electronic component including a semiconductor, and various semiconductor elements are selected according to the required functions.

[0021] As shown in Figure 1, the insulating circuit board 10 comprises a ceramic substrate 11 that serves as an insulating layer, a circuit layer 12 disposed on the first surface (upper surface in Figure 1) of the ceramic substrate 11, and a metal layer 13 formed on the second surface (lower surface in Figure 1) of the ceramic substrate 11.

[0022] The ceramic substrate 11 (insulating layer) prevents electrical connection between the circuit layer 12 and the metal layer 13, and is made of a highly insulating material such as AlN (aluminum nitride) or Si3N4 (silicon nitride). The thickness of the ceramic substrate 11 is set within the range of 0.2 mm to 1.5 mm. In this embodiment, AlN (aluminum nitride) is used as the ceramic substrate, and its thickness is set to 0.635 mm. Furthermore, when using Si3N4 (silicon nitride) as the ceramic substrate 11, the thickness is preferably 0.32 mm.

[0023] As shown in Figure 3, the circuit layer 12 is formed by joining metal pieces 22 made of copper, copper alloy, aluminum, or aluminum alloy to the first surface of the ceramic substrate 11. As copper or copper alloy, oxygen-free copper or tough pitch copper can be used. As aluminum or aluminum alloy, rolled sheets of aluminum with a purity of 99.99 mass% or higher (so-called 4N aluminum), A3003 alloy, A6063 alloy, etc. can be used. In this embodiment, the metal pieces 22 constituting the circuit layer 12 are made by punching out rolled sheets of oxygen-free copper. A circuit pattern is formed on this circuit layer 12 by bonding the aforementioned metal pieces 22 in a patterned manner, and its first surface (the top surface in Figure 1) is the mounting surface on which the semiconductor element 3 is mounted. Here, the thickness of the circuit layer 12 is set within the range of 0.1 mm to 3.0 mm, and in this embodiment it is set to 0.8 mm.

[0024] As shown in Figure 3, the metal layer 13 is formed by joining metal pieces 23 made of copper, copper alloy, aluminum, or aluminum alloy to the second surface of the ceramic substrate 11. The metal pieces 23 can be made of oxygen-free copper, tough pitch copper, aluminum with a purity of 99.99 mass% or higher (so-called 4N aluminum), A3003 alloy, A6063 alloy, or other rolled sheets. In this embodiment, rolled sheets of oxygen-free copper are used as the metal pieces 23 constituting the metal layer 13. Here, the thickness of the metal layer 13 is set within the range of 0.1 mm to 3.0 mm, and in this embodiment, it is set to 0.8 mm.

[0025] The heat sink 31 is for dissipating heat from the insulating circuit board 10. The heat sink 31 is made of a material with good thermal conductivity, and in this embodiment, it is made of aluminum or an aluminum alloy (for example, A6063 alloy). The thickness of this heat sink 31 is set within the range of 3 mm to 10 mm. Furthermore, the heat sink 31 and the metal layer 13 of the insulating circuit board 10 are solid-phase diffusion bonded.

[0026] Next, the manufacturing method of the insulating circuit board 10 according to this embodiment will be described with reference to Figures 2 to 5.

[0027] (Bonding paste printing process S01) First, the bonding paste 25 according to this embodiment is printed on the area of ​​the first surface of the ceramic substrate 11 where multiple metal pieces 22 are to be joined. Then, the bonding paste 25 according to this embodiment is printed on the area of ​​the second surface of the ceramic substrate 11 where metal pieces 23 are to be joined. After drying the printed bonding paste 25, the dried bonding paste 25a is placed on the first and second surfaces of the ceramic substrate 11, as shown in Figure 3. Furthermore, it is preferable to set the application thickness of the bonding paste 25 so that the bonding paste 25a after drying is in the range of 5 μm to 20 μm. In addition, it is preferable that the acrylic resin content be in the range of 3.2 mass% to 8.0 mass%. Furthermore, plasticizers consisting of adipic acid esters, such as diisononyl adipate, diisodecyl adipate, bis(2-ethylhexyl) adipate, and bis(2-butoxyethyl) adipate, can be used. As solvents, α-terpineol, texanol (3-hydroxy-2,2,4-trimethylpentyl isobutyrate), and butylcarbitol acetate can be used.

[0028] The bonding paste 25 used in this embodiment contains metal powder, acrylic resin, a plasticizer consisting of an adipic acid ester, and a solvent. Furthermore, the bonding paste 25 is specified to have a plasticizer content within the range of 3.2 mass% to 10.4 mass%, and the ratio A / B of the weight of the plasticizer A to the weight of the acrylic resin B is specified to be within the range of 0.2 ≤ A / B ≤ 1.3.

[0029] In this embodiment of the bonding paste 25, with the bonding paste being 100 mass%, the metal powder content is preferably in the range of 50 mass% to 90 mass%, and the solvent content is preferably in the range of 5.8 mass% to 31.6 mass%. Note that each content is calculated based on the total bonding paste 25 being considered as 100 mass%.

[0030] Furthermore, the metal powder is appropriately selected depending on the components to be joined. When joining ceramic substrates made of AlN or Si3N4 to copper or copper alloys, a brazing material containing active metals or hydrides of active metals such as Ag, Cu, and Ti is used. When joining ceramic substrates made of AlN or Si3N4 to aluminum or aluminum alloys, a brazing material mixed with aluminum and silicon, or aluminum and copper, is used. In this embodiment, since a ceramic substrate 11 made of AlN is joined to metal pieces 22 and 23 made of oxygen-free copper, a mixed powder of Ag powder and Ti powder, which is an active metal, is used as the metal powder. The mixing ratio (mass ratio) of Ag and Ti is set within the range of Ag / Ti = 1.2 to 26.7. When joining a ceramic substrate made of AlN or Si3N4 to aluminum or an aluminum alloy, a mixed powder of aluminum and silicon, or aluminum and copper, etc., is used. Furthermore, it is preferable that the average particle size of the metal powder be within the range of 1 μm to 5 μm.

[0031] Here, the bonding paste printing process S01 will be explained using Figures 4 and 5. In the bonding paste printing process S01, for example, the bonding paste 25 is printed on the first and second surfaces of the ceramic substrate 11 using the printing stage 50 shown in Figure 5.

[0032] In this printing stage 50, as shown in Figure 5, a recess 52 is formed that opens onto the mounting surface on which the ceramic substrate 11 is placed. The opening area of ​​this recess 52 on the mounting surface is slightly smaller than the area of ​​the ceramic substrate 11, and a support portion 53 is formed at the periphery of the recess 52 to support the end of the ceramic substrate 11. In this embodiment, a rib 54 is formed in the recess 52. The width of the rib is preferably 0.5 mm or more. The distance from the end of the printed bonding paste 25 to the rib 54 is preferably 0.1 mm or more. Furthermore, a suction section 55 is formed on the bottom side of the recess 52. This suction section 55 is located on the bottom side of the recess 52 and includes a chamber 56, a suction hole 57 that opens to the bottom surface of the recess 52 and communicates with the chamber 56, and a suction device 58.

[0033] In this case, it is preferable to set the depth of the recess 52 to be within the range of 10 to 20 times the printing thickness of the bonding paste 25 to be printed. Furthermore, it is preferable to set the width of the support portion 53 formed on the periphery of the recess 52 to be 1 mm or more. Furthermore, it is preferable to form the recess 52 and the support portion 53 such that the distance between the end of the support portion 53 and the end of the printed bonding paste 25 is within the range of 0.1 mm to 20 mm.

[0034] In the bonding paste printing process S01, the ceramic substrate 11 is placed on the recess 52 of the printing stage 50. In this embodiment, the ceramic substrate 11 has scribe lines 11A formed on it for division, and the ceramic substrate 11 is placed on the printing stage 50 such that these scribe lines 11A are located on the ribs 54 of the recess 52.

[0035] Then, the ceramic substrate 11 is fixed by suction using the suction unit 55, and bonding paste 25 is printed on the first surface of the ceramic substrate 11. It is preferable that the suction pressure at this time be within the range of 0.05 MPa to 0.2 MPa. Furthermore, it is preferable that the squeegee pressure (printing pressure) be within the range of 0.1 MPa to 0.2 MPa.

[0036] Next, the bonding paste 25 printed on the first surface of the ceramic substrate 11 is dried to form the bonded paste 25a after drying. Preferably, the drying conditions are a drying temperature within the range of 100°C to 155°C and a drying time within the range of 5 minutes to 30 minutes. Most of the solvent evaporates during this drying process. The drying atmosphere can be an air atmosphere, an inert atmosphere such as nitrogen or argon, or a vacuum atmosphere. In this embodiment, the bonding paste 25 contains an acrylic resin and a plasticizer consisting of an adipic acid ester, as described above. The plasticizer content is within the range of 3.2 mass% to 10.4 mass%, and the ratio A / B of the weight of the plasticizer A to the weight of the acrylic resin B is within the range of 0.2 ≤ A / B ≤ 1.3. As a result, the plasticizer remains even after drying, ensuring the tackiness of the acrylic resin, and thus tackiness is exhibited in the bonding paste 25a after drying.

[0037] Next, the ceramic substrate 11, on which the bonding paste 25 (bonding paste 25a after drying) is printed on the first surface, is inverted and placed on the recess 52 of the printing stage 50. In this embodiment, the ceramic substrate 11 has scribe lines 11A for division formed on it, and the ceramic substrate 11 is placed on the printing stage 50 so that these scribe lines 11A are located on the ribs 54 of the recess 52. By placing the ceramic substrate 11 in this way, the bonding paste 25 (bonding paste 25a after drying) printed on the first surface of the ceramic substrate 11 is contained in the recess 52.

[0038] Then, the ceramic substrate 11 is fixed by suction using the suction unit 55, and bonding paste 25 is printed on the second surface of the ceramic substrate 11. It is preferable that the suction pressure at this time be within the range of 0.05 MPa to 0.2 MPa. Furthermore, it is preferable that the squeegee pressure (printing pressure) be within the range of 0.1 MPa to 0.2 MPa.

[0039] Next, the bonding paste 25 printed on the second surface of the ceramic substrate 11 is dried to form the bonded paste 25a after drying. Preferably, the drying conditions are a drying temperature within the range of 100°C to 155°C and a drying time within the range of 5 minutes to 30 minutes. In this way, bonding paste 25 (bonding paste 25a after drying) is printed onto the first and second surfaces of the ceramic substrate 11.

[0040] (Lamination process S02) Next, a metal piece 22, which will become the circuit layer 12, is laminated onto the first surface of the divided ceramic substrate 11 via the dried bonding paste 25a, and a metal piece 23, which will become the metal layer 13, is laminated onto the second surface of the ceramic substrate 11. In this embodiment, in the lamination process S02, the laminated ceramic substrate 11 and metal pieces 22, 23, which are laminated via the bonding paste 25a after drying, may be pressed in the lamination direction. Preferably, the pressing conditions at this time are a pressing pressure within the range of 0.05 MPa to 0.5 MPa and a pressing time within the range of 5 seconds to 60 seconds.

[0041] In this embodiment, the bonding paste 25 contains metal powder, acrylic resin, a plasticizer consisting of adipic acid ester, and a solvent, with the plasticizer content being in the range of 3.2 mass% to 10.4 mass% and the ratio A / B of the weight of the plasticizer to the weight of the acrylic resin being in the range of 0.2 ≤ A / B ≤ 1.3. As a result, it has sufficient adhesive strength after drying, making it possible to suppress misalignment of the laminated metal pieces 22 and 23.

[0042] (Joining process S03) Then, the laminated ceramic substrate 11 and metal pieces 22 and 23 are heat-treated and joined via the bonding paste 25a after drying. The heating temperature is appropriately selected depending on the metal piece. If the metal piece is copper or a copper alloy, the temperature is set to be above the eutectic point of Ag and Cu; if it is aluminum or an aluminum alloy, the temperature is set to be above the eutectic point of aluminum and the metal contained in the bonding metal paste. In this embodiment, since oxygen-free copper is used as the metal layers 22 and 23, the heating temperature in joining step S03 is set to be above the eutectic temperature of Ag and Cu, specifically within the range of 790°C to 830°C. The holding time in joining step S03 is set within the range of 5 minutes to 60 minutes. Preferably, the heating temperature in joining step S03 is within the range of 800°C to 820°C. Preferably, the holding time in joining step S03 is within the range of 10 minutes to 30 minutes. Furthermore, while there are no particular limitations on the cooling rate after heating and holding, it is preferable that it be within the range of 2°C / min to 10°C / min.

[0043] (Dividing process S04) Next, the ceramic substrate 11, on which the metal piece 22 is bonded to the first surface and the metal piece 23 is bonded to the second surface, is divided along the scribe line 11A.

[0044] The insulating circuit board 10 of this embodiment is manufactured through the process described above.

[0045] (Heat sink bonding process S05) Next, a heat sink 31 is laminated on the other side of the metal layer 13 of the insulating circuit board 10. The laminate of the insulating circuit board 10 and the heat sink 31 is then placed in a vacuum heating furnace under pressure in the lamination direction using a pressurizing device, and held at a heating temperature below the eutectic temperature of aluminum and copper, thereby solid-phase diffusion bonding of the metal layer 13 and the heat sink 31. The bonding conditions in this heat sink bonding process S05 are: vacuum conditions are 10 -3 The temperature is set to be below Pa, the heating temperature is within the range of 510°C to 545°C, and the holding time at the heating temperature is within the range of 45 minutes to 120 minutes.

[0046] (Semiconductor device bonding process S06) Next, semiconductor elements 3 are stacked on one side of the circuit layer 12 via solder material and soldered together in a heating furnace. As described above, the power module 1 shown in Figure 1 is manufactured.

[0047] According to the manufacturing method for an insulating circuit board of this embodiment, which has the above configuration, in the bonding paste printing step S01, bonding paste 25 is printed on the first surface of the ceramic substrate 11, dried, and then the inverted ceramic substrate 11 is placed on the printing stage 50. The bonding paste 25 printed on the first surface of the ceramic substrate 11 (bonding paste 25a after drying) is contained in the recess 52, and with the ceramic substrate 11 fixed by the suction unit 55, bonding paste 25 is printed on the second surface of the ceramic substrate 11. As a result, when printing bonding paste 25 on the second surface, contact between the bonding paste 25 printed on the first surface (bonding paste 25a after drying) and the printing stage 50 is suppressed, and bonding paste 25 can be stably printed on the first and second surfaces of the ceramic substrate 11. Furthermore, since the ceramic substrate 11 is fixed by the suction unit 55, bonding paste 25 can be printed on the second surface of the ceramic substrate 11 with high precision.

[0048] In this embodiment, the bonding paste 25 is printed on the first surface of the ceramic substrate 11, the printed bonding paste 25 is dried, and then the bonding paste 25 is printed on the second surface of the ceramic substrate 11. Therefore, even if the bonding paste 25a is tacky after drying, contact between the dried bonding paste 25a and the printing stage 50 is suppressed when printing the bonding paste 25 on the second surface of the ceramic substrate 11, and the bonding paste 25 can be stably printed on both the first and second surfaces of the ceramic substrate 11.

[0049] Furthermore, in this embodiment, scribe lines 11A are formed on the ceramic substrate 11, and ribs 54 are provided in the recess 52 of the printing stage 50 at positions corresponding to the scribe lines 11A on the placed ceramic substrate 11. Therefore, even with a large ceramic substrate 11, deflection of the ceramic substrate 11 during suction fixing and printing can be suppressed, and the bonding paste 25 can be printed stably. In addition, after printing the bonding paste 25, the ceramic substrate 11 can be divided along the scribe lines 11A, making it possible to efficiently manufacture multiple insulating circuit boards 10.

[0050] Furthermore, in this embodiment, the bonding paste 25 contains metal powder, acrylic resin, a plasticizer consisting of adipic acid ester, and a solvent, with the plasticizer content being in the range of 3.2 mass% to 10.4 mass% and the ratio A / B of the weight A of the plasticizer to the weight B of the acrylic resin being in the range of 0.2 ≤ A / B ≤ 1.3, thus providing sufficient adhesive strength. Moreover, as described above, since a printing stage 50 having recesses 52 is used, the bonding paste 25 can be stably printed on the first and second surfaces of the ceramic substrate 11.

[0051] Although embodiments of the present invention have been described above, the present invention is not limited thereto and can be modified as appropriate without departing from the technical spirit of the invention.

[0052] For example, in this embodiment, a power module is described as being constructed by mounting power semiconductor elements on the circuit layer of an insulating circuit board, but the invention is not limited to this. For example, an LED module may be constructed by mounting LED elements on an insulating circuit board, or a thermoelectric module may be constructed by mounting thermoelectric elements on the circuit layer of an insulating circuit board.

[0053] Furthermore, although this embodiment describes the bonding of the insulating circuit board (metal layer) and the heat sink by solid-phase diffusion bonding, it is not limited to this, and other bonding methods such as brazing and TLP may be applied. Furthermore, although this embodiment describes the heat sink as being made of aluminum, it is not limited to this and may be made of copper or other materials, or it may have a channel through which a cooling medium flows.

[0054] Furthermore, although this embodiment describes the use of a ceramic substrate with scribe lines formed on it and the formation of ribs in the recesses of the printing stage, it is not limited to this, and bonding paste may be printed on a ceramic substrate without scribe lines using a printing stage having recesses without ribs.

[0055] Furthermore, although this embodiment describes a configuration in which the bonding paste is printed and then dried, it is not limited to this, and drying may not be performed. Furthermore, in this embodiment, a bonding paste containing metal powder, acrylic resin, a plasticizer consisting of an adipic acid ester, and a solvent was described as an example, but the invention is not limited to this, and bonding pastes of other compositions may be used. Furthermore, in this embodiment, the circuit layer 12 is formed on the first surface of the ceramic substrate 11 and the metal layer 13 is formed on the second surface. However, the metal layer 13 may be formed on the first surface and the circuit layer 12 on the second surface. [Explanation of Symbols]

[0056] 1 Power Module 3 Semiconductor elements 10 Insulated circuit board 11. Ceramic substrate 12 circuit layers 13 Metal layer 22 metal piece 23 metal piece 25 Bonding paste 50 Printing Stages 52 recess 53 Support part 54 Ribs 55 Suction part

Claims

1. A method for manufacturing an insulating circuit board comprising a ceramic substrate and a circuit layer and a metal layer formed by joining metal pieces to a first surface and a second surface of the ceramic substrate, respectively, A bonding paste printing step in which bonding paste is printed on the first surface and the second surface of the ceramic substrate, respectively, A lamination step of laminating the ceramic substrate and the metal piece that will become the circuit layer via the bonding paste, and laminating the ceramic substrate and the metal piece that will become the metal layer via the bonding paste, A bonding step in which the stacked metal pieces and the ceramic substrate are heat-treated to bond the metal pieces and the ceramic substrate, It has, In the bonding paste printing process, the bonding paste is printed on the first surface of the ceramic substrate, then the ceramic substrate is inverted and placed on a printing stage having a recess on its mounting surface, and the bonding paste is printed on the second surface of the ceramic substrate. In the printing stage, a support portion is formed on the periphery of the recess to support the end of the ceramic substrate, and a suction portion is formed on the bottom side of the recess. A method for manufacturing an insulating circuit board, characterized in that when the inverted ceramic substrate is placed on the circuit board, the bonding paste printed on the first surface is contained within the recess, and the bonding paste is printed on the second surface of the ceramic substrate while the ceramic substrate is fixed in place by the suction part.

2. The method for manufacturing an insulating circuit board according to claim 1, characterized in that the bonding paste is printed on the first surface of the ceramic substrate, the printed bonding paste is dried, and then the bonding paste is printed on the second surface of the ceramic substrate.

3. A method for manufacturing an insulating circuit board according to claim 1 or claim 2, characterized in that the ceramic substrate has scribe lines formed on it, and the recess is provided with ribs at positions corresponding to the scribe lines on the placed ceramic substrate.

4. The method for manufacturing an insulating circuit board according to claim 1 or 2, characterized in that the bonding paste contains metal powder, acrylic resin, a plasticizer consisting of an adipic acid ester, and a solvent, wherein the content of the plasticizer is in the range of 3.2 mass% to 10.4 mass%, and the ratio A / B of the weight A of the plasticizer to the weight B of the acrylic resin is in the range of 0.2 ≤ A / B ≤ 1.3.

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