Metal paste for bonding, method for manufacturing a bonded body, method for manufacturing an insulating circuit board

Abstract

To provide a metal paste for bonding that can suppress misalignment of parts to be bonded without using a temporary fixing material and that can be bonded with good positioning accuracy.SOLUTION: It is characterized in that it contains metal powder, acrylic resin, a plasticizer comprising adipic acid ester, and a solvent, the content of the plasticizer is within the range of 3.2 mass% to 10.4 mass% or inclusive, and the ratio A / B of the mass A of the plasticizer to the mass B of the acrylic resin is within the range of 0.2≤A / B≤1.3.SELECTED DRAWING: None

Description

Technical Field

[0001] This invention relates to a bonding metal paste used when bonding members, a method for manufacturing a bonded body using this bonding metal paste, and a method for manufacturing an insulating circuit board.

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 bonded to an insulating circuit board having a circuit layer made of a conductive material formed on one surface of an insulating layer. In addition, in the above-mentioned insulating circuit board, there is provided a structure in which a metal piece having excellent conductivity is bonded to one surface of the insulating layer to form a circuit layer, and a metal piece having excellent heat dissipation is bonded to the other surface 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, in which a heat sink is bonded to the other surface side of the insulating layer, is also provided.

[0003] For example, Patent Document 1 discloses an insulating circuit board in which a circuit layer is formed by bonding an aluminum piece to one surface of a ceramic substrate, and a metal layer is formed by bonding an aluminum piece to the other surface, and a power module including a semiconductor element bonded to this circuit layer via a solder material. In addition, Patent Document 2 proposes an insulating circuit board in which an aluminum piece is bonded to one surface of a ceramic substrate, and a circuit layer in which an aluminum layer and a copper layer are laminated is formed by solid-phase diffusion bonding of a copper piece to this aluminum piece. Furthermore, Patent Document 3 discloses an LED module having a structure in which a conductive circuit layer is formed on one surface of a base material made of ceramics, a heat radiator is bonded to the other surface of the insulating substrate, and a light-emitting element is mounted on the circuit layer.

[0004] In cases where ceramic substrates are joined to metal pieces, aluminum pieces to copper pieces, insulating circuit boards to heat sinks, etc., as described in Patent Documents 4-6, for example, a temporary fixing material containing organic substances such as polyethylene glycol (PEG) is used between the members to be joined. The members are then aligned and temporarily fixed, and then pressurized and heated in the stacking direction to join them. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 3171234 [Patent Document 2] Patent No. 5403129 [Patent Document 3] Japanese Patent Publication No. 2015-070199 [Patent Document 4] Japanese Patent Publication No. 2014-175425 [Patent Document 5] Japanese Patent Publication No. 2014-209591 [Patent Document 6] Japanese Patent Publication No. 2016-105452 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, as mentioned above, when using temporary fastening material to temporarily fasten metal pieces, the application and drying processes of the temporary fastening material are required, which increases the manufacturing process and may make it difficult to efficiently manufacture insulated circuit boards. Furthermore, it may increase manufacturing costs. Furthermore, when forming a circuit layer by temporarily fixing metal pieces with a temporary fixing material and then joining the metal pieces by applying pressure and heating, there was a risk that some of the temporary fixing material would carbonize during heating, adhering to the spaces between circuit patterns as carbon residue, resulting in insufficient insulation between the patterns of the circuit layer.

[0007] This invention has been made in view of the circumstances described above, and aims to provide a metal paste for joining that can suppress misalignment of members to be joined without using a temporary fixing material and can join them with high positional accuracy, as well as a method for manufacturing a joined body using this metal paste for joining, and a method for manufacturing an insulating circuit board. [Means for solving the problem]

[0008] To solve the above-mentioned problems, the bonding metal paste of embodiment 1 of the present invention 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 mass A of the plasticizer to the mass B of the acrylic resin is in the range of 0.2 ≤ A / B ≤ 1.3.

[0009] According to the bonding metal paste of embodiment 1 of the present invention, the paste contains an acrylic resin and a plasticizer consisting of an adipic acid ester, 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 mass A of the plasticizer to the mass B of the acrylic resin is in the range of 0.2 ≤ A / B ≤ 1.3. As a result, sufficient adhesive strength is achieved when this bonding metal paste is applied and dried, and misalignment of the members to be joined can be suppressed without the use of a temporary fixing material. Therefore, it becomes possible to join the members to be joined with high positional accuracy.

[0010] A method for manufacturing a joined body according to aspect 2 of the present invention is a method for manufacturing a joined body in which a first member and a second member are joined, comprising: a joining metal paste application step of applying a joining metal paste according to aspect 1 of the present invention to at least one or both of the joining surfaces of the first member and the second member; a drying step of drying the applied joining metal paste; a lamination step of laminating the first member and the second member via the dried joining metal paste; and a joining step of heat-treating and joining the first member and the second member that have been laminated via the joining metal paste, wherein the lamination step is characterized in that the tackiness of the dried joining metal paste suppresses misalignment between the first member and the second member.

[0011] According to the method for manufacturing a joined body of embodiment 2 of the present invention, the above-mentioned joining metal paste is applied and dried, and then the first member and the second member are laminated together. The adhesive force of the joining metal paste after drying suppresses misalignment between the first member and the second member. Therefore, misalignment between the first member and the second member can be reliably suppressed without using a temporary fixing material, and the first member and the second member can be joined with high positional accuracy.

[0012] The method for manufacturing a bonded body according to aspect 3 of the present invention is characterized in that, in the method for manufacturing a bonded body according to aspect 2 of the present invention, in the lamination step, the first member and the second member, which are laminated via the bonding metal paste after drying, are subjected to pressure in the lamination direction, wherein the pressure is within the range of 0.05 MPa to 0.5 MPa and the pressurizing time is within the range of 5 seconds to 60 seconds. According to the method for manufacturing a joined body of embodiment 3 of the present invention, in the lamination process, the first member and the second member, which are laminated via the dried joining metal paste, are pressed in the lamination direction under the above-described pressing conditions. This makes it possible to further reliably suppress misalignment between the first member and the second member, and to join the first member and the second member with even greater positional accuracy.

[0013] 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 comprising an insulating layer and a circuit layer in which a metal piece is bonded to one surface of the insulating layer, comprising: a bonding metal paste application step of applying the bonding metal paste described above to at least one or both of the bonding surfaces of the insulating layer and the metal piece; a drying step of drying the applied bonding metal paste; a lamination step of laminating the insulating layer and the metal piece via the bonded metal paste after drying; and a bonding step of heat-treating and bonding the insulating layer and the metal piece laminated via the bonded metal paste, wherein the lamination step is characterized in that the adhesive force of the bonded metal paste after drying suppresses misalignment between the insulating layer and the metal piece.

[0014] According to the method for manufacturing an insulating circuit board of embodiment 4 of the present invention, the above-mentioned bonding metal paste is applied and dried, and then the insulating layer and the metal piece are laminated. The adhesive force of the bonding metal paste after drying suppresses misalignment between the insulating layer and the metal piece. Therefore, misalignment between the insulating layer and the metal piece can be reliably suppressed without using a temporary fixing material, and the insulating layer and the metal piece can be joined with high positional accuracy.

[0015] A method for manufacturing an insulating circuit board according to aspect 5 of the present invention is characterized in that, in the method for manufacturing an insulating circuit board according to aspect 4 of the present invention, in the lamination step, the insulating layer and the metal piece laminated via the bonding metal paste after drying are subjected to pressure in the lamination direction, wherein the pressure is within the range of 0.05 MPa to 0.5 MPa and the pressure is within the range of 5 seconds to 60 seconds. According to the method for manufacturing an insulating circuit board of embodiment 4 of the present invention, in the lamination process, the insulating layer and the metal piece, which are laminated via the bonding metal paste after drying, are pressed in the lamination direction under the above-described pressurizing conditions. This makes it possible to further reliably suppress misalignment between the insulating layer and the metal piece, and to bond the insulating layer and the metal piece with even greater positional accuracy. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a joining metal paste that can suppress displacement of a member to be joined without using a temporary fixing material and can join with high positional accuracy, a method for manufacturing a joined body using this joining metal paste, and a method for manufacturing an insulating circuit board.

Brief Description of Drawings

[0017] [Figure 1] FIG. 9 is a 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] FIG. 12 is a flowchart showing the method for manufacturing the insulating circuit board shown in FIG. 1. [Figure 3] FIG. 15 is an explanatory view showing the method for manufacturing the insulating circuit board shown in FIG. 1. [Figure 4] FIG. 18 is an explanatory view showing the method for manufacturing the insulating circuit board shown in FIG. 1.

Embodiments for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0019] FIG. 30 shows an insulating circuit board 10 manufactured by the method for manufacturing an insulating circuit board using a joining metal paste according to an embodiment of the present invention, and a power module 1 using this insulating circuit board 10.

[0020] This power module 1 includes an insulating circuit board 10, a semiconductor element 3 joined to one side (upper side in FIG. 1) of the insulating circuit board 10 via a solder layer 2, and a heat sink 31 disposed on the other side (lower side in FIG. 1) of the insulating circuit board 10.

[0021] 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 equipped with a semiconductor, and various semiconductor elements are selected according to the required function.

[0022] 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 one side of the ceramic substrate 11 (the upper surface in Figure 1), and a metal layer 13 formed on the other side of the ceramic substrate 11 (the lower surface in Figure 1).

[0023] 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, it is preferable that the thickness be 0.32 mm.

[0024] As shown in Figures 3 and 4, the circuit layer 12 is formed by joining a metal piece 22 made of copper, copper alloy, aluminum, or aluminum alloy to one side of the ceramic substrate 11. The adhesive strength of the paste is proportional to the ratio of the contact area of ​​the metal piece 22 to the application area of ​​the paste. In this embodiment, it is assumed that the entire bonding surface of the metal piece 22 is in contact with the paste. 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 piece 22 constituting the circuit layer 12 is made by punching out a rolled sheet 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 one side of it (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.

[0025] As shown in Figures 3 and 4, the metal layer 13 is formed by joining metal pieces 23 made of copper, copper alloy, aluminum, or aluminum alloy to the other surface of the ceramic substrate 11. The adhesive strength of the paste is proportional to the ratio of the contact area of ​​the metal pieces 23 to the application area of ​​the paste. In this embodiment, it is assumed that the entire bonding surface of the metal pieces 23 is in contact with the paste. As the metal pieces 23, they can be made of oxygen-free copper, tough pitch copper, rolled aluminum with a purity of 99.99 mass% or higher (so-called 4N aluminum), A3003 alloy, A6063 alloy, etc. In this embodiment, rolled plates 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.

[0026] 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.

[0027] Next, the method for manufacturing an insulating circuit board according to this embodiment will be explained using Figures 2 to 4.

[0028] (Metal paste application process for bonding S01) First, as shown in Figure 3, the bonding metal paste 25 according to this embodiment is applied to the area on one side of the ceramic substrate 11 (first member) where multiple metal pieces 22 (second member) are to be joined. Then, the bonding metal paste 25 according to this embodiment is applied to the area on the other side of the ceramic substrate 11 (first member) where metal pieces 23 (second member) are to be joined. Furthermore, it is preferable to set the coating thickness of the bonding metal paste 25 to be within the range of 5 μm to 20 μm after the drying process S02 described later.

[0029] Here, we will describe the bonding metal paste 25, which is part of this embodiment. The bonding metal paste 25 in this embodiment contains metal powder, acrylic resin, a plasticizer consisting of an adipic acid ester, and a solvent. In this embodiment of the bonding metal paste 25, the plasticizer content is within the range of 3.2 mass% to 10.4 mass%, and the ratio A / B of the mass of the plasticizer A to the mass of the acrylic resin B is within the range of 0.2 ≤ A / B ≤ 1.3. Furthermore, it is preferable that the acrylic resin content be within 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.

[0030] In this embodiment, the bonding metal paste 25 is preferably composed of 100 mass%, with the metal powder content being in the range of 50 mass% to 90 mass%, and the solvent content being in the range of 5.8 mass% to 31.6 mass%. Note that each content is based on a bonding metal paste content of 100 mass%.

[0031] Furthermore, the metal powder is appropriately selected depending on the components to be joined. When joining a ceramic substrate made of AlN or Si3N4 to copper or a copper alloy, a mixed powder or alloy powder containing active metals such as Ag, Cu, and Ti, or hydrides of active metals, is used. 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, 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 within the range of Ag / Ti = 1.2 to 26.7. Furthermore, it is preferable that the average particle size of the metal powder be within the range of 1 μm to 5 μm.

[0032] (Drying process S02) Next, the applied bonding metal paste 25 is dried. 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 drying step S02, most of the solvent will evaporate. The drying atmosphere can be an air atmosphere, an inert atmosphere such as nitrogen or argon, or a vacuum atmosphere. In this embodiment of the bonding metal paste 25, as described above, it contains an acrylic resin and a plasticizer consisting of an adipic acid ester, with the plasticizer content being in the range of 3.2 mass% to 10.4 mass%, and the ratio A / B of the mass A of the plasticizer to the mass B of the acrylic resin being in the range of 0.2 ≤ A / B ≤ 1.3. As a result, the plasticizer remains even after the drying process S02, ensuring the tackiness of the acrylic resin, and thus tackiness is exhibited in the bonding metal paste 25a after drying.

[0033] In order to further enhance the adhesive strength of the bonding metal paste 25a after drying, it is preferable to set the lower limit of the plasticizer content to 3.4 mass% or more, and more preferably to 3.5 mass% or more. On the other hand, it is preferable to set the upper limit of the plasticizer content to 6.0 mass% or less, and more preferably to 5.0 mass% or less. Furthermore, it is preferable that the ratio A / B of the mass A of the plasticizer to the mass B of the acrylic resin be 0.2 or higher, and more preferably 0.4 or higher. On the other hand, it is preferable that the ratio A / B of the mass A of the plasticizer to the mass B of the acrylic resin be 1.3 or lower, and more preferably 1.0 or lower.

[0034] (Lamination process S03) Next, metal pieces 22 that will become the circuit layer 12 are laminated onto one side of the ceramic substrate 11 via the dried bonding metal paste 25a, and metal pieces 23 that will become the metal layer 13 are laminated onto the other side of the ceramic substrate 11. At this time, a circuit pattern is formed on one side of the ceramic substrate 11 by arranging a plurality of metal pieces 22 in a pattern.

[0035] In this embodiment, in the lamination process S03, the laminated ceramic substrate 11 and metal pieces 22, 23, which are laminated via the bonded metal 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.

[0036] (Joining process S04) Then, the laminated ceramic substrate 11 and metal pieces 22 and 23 are heat-treated and joined via the dried bonding metal paste 25a. The heating temperature is appropriately selected depending on the metal pieces to be joined. 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 S04 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 S04 is set within the range of 5 minutes to 60 minutes. Preferably, the heating temperature in joining step S04 is within the range of 800°C to 820°C. Preferably, the holding time in joining step S04 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.

[0037] The insulating circuit board 10 of this embodiment is manufactured through the process described above.

[0038] (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.

[0039] (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.

[0040] The bonding metal paste 25 of this embodiment, configured as described above, contains an acrylic resin and a plasticizer consisting of an adipic acid ester. The plasticizer content is within the range of 3.2 mass% to 10.4 mass%, and the ratio A / B of the mass A of the plasticizer to the mass B of the acrylic resin is within the range of 0.2 ≤ A / B ≤ 1.3. As a result, sufficient adhesive strength (for example, an adhesive strength of 0.02 MPa to 1.0 MPa) is achieved in the bonding metal paste 25a after drying, and positional misalignment between the ceramic substrate 11 and the metal pieces 22 and 23 to be bonded can be suppressed without using a temporary fixing material. Therefore, it becomes possible to bond the metal pieces 22 and 23 with high positional accuracy. Furthermore, according to this embodiment, when temporarily fixing metal pieces using a temporary fixing material, it is possible to avoid the problem that a portion of the temporary fixing material carbonizes and adheres to the circuit patterns, becoming a carbon residue and resulting in insufficient insulation between the patterns of the circuit layer.

[0041] Furthermore, according to the method for manufacturing an insulating circuit board of this embodiment, the ceramic substrate 11 and the metal pieces 22 and 23 are laminated via a bonding metal paste 25a after drying. The adhesive force of the bonding metal paste 25a after drying suppresses misalignment between the ceramic substrate 11 and the metal pieces 22 and 23. Therefore, misalignment between the ceramic substrate 11 and the metal pieces 22 and 23 can be reliably suppressed without using a temporary fixing material, and the ceramic substrate 11 and the metal pieces 22 and 23 can be joined with high positional accuracy.

[0042] Furthermore, in the lamination process S03, if the ceramic substrate 11 and metal pieces 22,23, which are laminated via the dried bonding metal paste 25a, are pressed in the lamination direction under pressurizing conditions within the range of pressurizing pressure: 0.05 MPa to 0.5 MPa and pressurizing time: 5 seconds to 60 seconds, the misalignment between the ceramic substrate 11 and the metal pieces 22,23 can be suppressed even more reliably, and the ceramic substrate 11 and the metal pieces 22,23 can be joined with even greater positional accuracy.

[0043] 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.

[0044] 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. Furthermore, although this embodiment describes an insulating layer made of a ceramic substrate, it is not limited to this, and the insulating layer may be made of acrylic resin or the like.

[0045] 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. [Examples]

[0046] The results of the verification experiments conducted to confirm the effects of the present invention are described below.

[0047] Ceramic substrates (40mm × 40mm × 0.635mmt (AlN), 40mm × 40mm × 0.32mmt (Si3N4)) and metal pieces made of oxygen-free copper (37mm × 37mm × 0.8mmt) were prepared as shown in Table 2. Then, a bonding metal paste with the composition shown in Table 1 was prepared. A bonding metal paste was applied to one side of a ceramic substrate, and then dried under the conditions shown in Table 2. The thickness of the bonding metal paste was adjusted to 5 to 20 μm after drying.

[0048] Metal pieces were layered onto a dried bonding metal paste. Pressure was applied in the layering direction at the pressure and duration shown in Table 2. Furthermore, on one side of the ceramic substrate, two metal pieces were arranged so that the distance between the circuit patterns (the distance between the metal pieces) was 1.0 mm in order to form a circuit pattern. Next, the material was heated under the conditions shown in Table 2, and then heat-treated by cooling from the heating temperature to 700°C at a rate of 3°C / min to bond the ceramic substrate and the metal piece, thereby manufacturing an insulating circuit board (jointed body).

[0049] The following items were evaluated:

[0050] (Market share strength) The shear strength of ceramic substrates and metal pieces laminated via a bonding metal paste after drying was measured using a Resca PTR-1101 bonding tester. The tool was placed against the side of the metal piece and moved horizontally relative to the ceramic substrate, and the load applied when the metal piece separated from the paste was measured. The shear speed (speed at which the tool was moved) was set to 0.05 mm / s. The evaluation results are shown in Table 2.

[0051] (Assessment of bonding properties) The bonding ratio at the bonding interface between the ceramic substrate and the metal piece after bonding was evaluated using an ultrasonic flaw detection device (FineSAT200 manufactured by Hitachi Power Solutions, Ltd.) and calculated using the following formula. Here, the initial bonding area was defined as the area to be bonded before bonding, i.e., the area of ​​the circuit layer. Since delamination is shown as a white area within the bonded portion in the binarized image of the ultrasonic flaw detection image, the area of ​​this white area was defined as the delamination area (non-bonded area). (Bonding rate)={(Initial bonding area)-(Non-bonding area)} / (Initial bonding area)×100

[0052] [Table 1]

[0053] [Table 2]

[0054] In Comparative Example 1, the plasticizer content, consisting of diisononyl adipicate, was 3.0 mass%, resulting in insufficient adhesion of the bonding metal paste and a shear strength of 0 MPa. In Comparative Example 2, the plasticizer content, consisting of diisononyl adipicate, was 10.6 mass%, resulting in insufficient adhesion of the bonding metal paste and a shear strength of 0 MPa. In Comparative Example 3, the mass ratio A / B of plasticizer A to acrylic resin B was 0.1, resulting in insufficient adhesion of the bonding metal paste and a shear strength of 0 MPa. In Comparative Example 4, the mass ratio A / B of plasticizer A to acrylic resin B was 1.4, resulting in insufficient adhesion of the bonding metal paste and a shear strength of 0 MPa. In Comparative Example 5, the material did not contain a plasticizer, resulting in insufficient adhesion of the bonding metal paste and a shear strength of 0 MPa.

[0055] In contrast, in Examples 1 to 7 of the present invention, the content of the plasticizer consisting of adipic acid ester is within the range of 3.2 mass% to 10.4 mass%, and the ratio A / B of the mass A of the plasticizer to the mass B of the acrylic resin is within the range of 0.2 ≤ A / B ≤ 1.3, thereby ensuring the adhesive strength of the bonding metal paste and achieving a shear strength of 0.02 MPa or higher.

[0056] The results of this embodiment confirm that, according to the present invention, it is possible to provide a bonding metal paste that can suppress misalignment of members to be joined without using a temporary fixing material and can be joined with high positional accuracy, as well as a method for manufacturing an insulating circuit board (a method for manufacturing a joined body) using this bonding metal paste. [Explanation of Symbols]

[0057] 1 Power Module 3 Semiconductor elements 10 Insulated circuit board 11. Ceramic substrate (insulating layer) 12 circuit layers 13 Metal layer 22 metal piece 23 metal piece

Claims

1. It contains metal powder, acrylic resin, a plasticizer consisting of adipic acid ester, and a solvent. A bonding metal paste characterized in that the content of the plasticizer is within the range of 3.2 mass% to 10.4 mass%, and the ratio A / B of the mass A of the plasticizer to the mass B of the acrylic resin is within the range of 0.2 ≤ A / B ≤ 1.

3.

2. A method for manufacturing a joint in which a first member and a second member are joined together, A bonding metal paste application step of applying the bonding metal paste described in claim 1 to at least one or both of the joining surfaces of the first member and the second member, A drying step to dry the applied bonding metal paste, A lamination step in which the first member and the second member are laminated via the bonding metal paste after drying, A joining step of joining the first member and the second member, which are laminated via the aforementioned joining metal paste, by heat treatment, It is equipped with, A method for manufacturing a bonded body, characterized in that, in the lamination step, the adhesive force of the bonding metal paste after drying suppresses misalignment between the first member and the second member.

3. The method for manufacturing a bonded body according to claim 2, wherein the lamination step involves applying pressure in the lamination direction to the first member and the second member that have been laminated via the bonding metal paste after drying, and the pressure applied is within the range of 0.05 MPa to 0.5 MPa, and the pressurizing time is within the range of 5 seconds to 60 seconds.

4. A method for manufacturing an insulating circuit board comprising an insulating layer and a circuit layer in which a metal piece is bonded to one side of the insulating layer, A bonding metal paste application step of applying the bonding metal paste described in claim 1 to at least one or both of the bonding surfaces of the insulating layer and the metal piece, A drying step to dry the applied bonding metal paste, A lamination step in which the insulating layer and the metal piece are laminated via the bonding metal paste after drying, A joining step in which the insulating layer and the metal piece, which are laminated via the aforementioned bonding metal paste, are heat-treated to join them, It is equipped with, A method for manufacturing an insulating circuit board, characterized in that, in the lamination step, the adhesive force of the bonding metal paste after drying suppresses misalignment between the insulating layer and the metal piece.

5. The method for manufacturing an insulating circuit board according to claim 4, characterized in that the lamination step involves applying pressure in the lamination direction to the insulating layer and the metal piece laminated via the bonding metal paste after drying, wherein the pressure applied is within the range of 0.05 MPa to 0.5 MPa and the pressurizing time is within the range of 5 seconds to 60 seconds.

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