Power module

Abstract

The present invention has: a heat dissipation insulating layer (101); a metal circuit pattern (103) provided in direct contact with one surface of the heat dissipation insulating layer (101); a power semiconductor element (105) mounted on the circuit pattern (103); a metal plate (107) provided in direct contact with the other surface of the heat dissipation insulating layer (101); a cooler (109) disposed facing a surface of the metal plate (107), the surface being the reverse of the surface facing the heat dissipation insulating layer (101); and a first bonding layer (111) for bonding the metal plate (107) and the cooler (109), wherein the first bonding layer (111) is formed from a heat-treated product of a conductive paste-containing component (A) of metal particles and component (B) of a thermosetting resin, and a storage modulus E'250 in heating of the conductive paste measured at 250 °C is 0.7 GPa to 5 GPa.

Description

Power module

[0001] This invention relates to a power module.

[0002] One technology for combining a cooling element with a power module is described in Patent Document 1 (Japanese Patent Application Publication No. 2020-72101). This document describes a power unit comprising a power module and a heat sink, wherein the power module has a sealing resin, a metal plate with one surface exposed to the sealing resin, and a circuit section installed on the opposite side of the metal plate from the aforementioned surface and sealed in the sealing resin, and the heat sink has a recess, the bottom surface of the recess is positioned inward from the edge of the upper opening of the recess in a plan view via a distance, and has a raised portion extending from the outer edge of the bottom surface toward the edge of the upper opening, the bottom of the power module is positioned inward from the raised portion and the aforementioned surface of the metal plate is thermally and mechanically connected to the bottom surface (Claim 1). It is stated that this improves heat dissipation, manufacturing precision, and the strength and ease of assembly of the heat sink in a power unit in which the power module is assembled to a heat sink (Paragraph 0005).

[0003] Japanese Patent Publication No. 2020-72101

[0004] However, when the present inventors examined the technology described in Patent Document 1, it became clear that there is room for improvement in power modules equipped with a cooler, in terms of suppressing warping and improving adhesion and thermal conductivity.

[0005] The present invention provides a power module that reduces warping and offers excellent adhesion and thermal conductivity between the cooler and adjacent components.

[0006] The present invention provides the following power module, conductive paste, structure, and method for manufacturing the same: [1] A heat dissipation insulating layer; a metal circuit pattern provided in direct contact with one surface of the heat dissipation insulating layer; a power semiconductor element mounted on the circuit pattern; a metal plate provided in direct contact with the other surface of the heat dissipation insulating layer; a cooler positioned opposite to the back surface of the metal plate opposite to the heat dissipation insulating layer; and a bonding layer joining the metal plate and the cooler, wherein the bonding layer is formed from a heat-treated conductive paste containing the following components (A) and (B), and the thermal storage modulus E' of the conductive paste is measured at 250°C by the following method 1. 250 However, the power module has a pressure of 0.7 GPa or more and 5 GPa or less. (A) Metal particles (B) Thermosetting resin (Method 1) The conductive paste is applied to a glass plate and heated in a nitrogen atmosphere from 30°C to 175°C over 60 minutes, and then sintered at 175°C for 120 minutes. This yields a cured product with a thickness of 0.05 mm. The storage modulus E' of the obtained cured product at 250°C is measured using a dynamic viscoelasticity analyzer (DMA) at a frequency of 10 Hz. 250 [1] The power module according to [1], wherein component (A) comprises spherical silver particles and flaky silver particles, and heat treatment causes component (A) to form a silver particle linkage structure. [2] The power module according to [1] or [2], wherein component (B) comprises one or more selected from the group consisting of epoxy resin, (meth)acrylic resin, silicone resin, and butadiene rubber. [4] The power module according to any one of [1] to [3], wherein the material of the cooler on the surface facing the heat dissipation insulating layer is copper or aluminum, and the bonding layer is provided in direct contact with the facing surface. [5] The storage modulus E' of the conductive paste, measured at 25°C by a method similar to method 1. 25A power module according to any one of [1] to [4], wherein the thermal conductivity is 5 GPa or more and 20 GPa or less. [6] A power module according to any one of [1] to [5], wherein the thermal conductivity of the hardened product of the conductive paste, measured by the following method 2, is 10 W / (m·K) or more and 50 W / (m·K) or less in the thickness direction. (Method 2) The conductive paste is applied to a glass plate and heated in a nitrogen atmosphere from 30°C to 175°C over 60 minutes, and then sintered at 175°C for 120 minutes. A hardened product with a thickness of 0.7 mm is obtained. The thermal conductivity λ (W / mK) of the obtained hardened product at 25°C is measured using the laser flash method. [7] The die shear strength of the Al / heat-treated product of the conductive paste / Cu laminate, measured by the following method 3, is 10 N / mm 2 The power module described in any one of [1] to [6] above. (Method 3) The conductive paste is applied to an aluminum plate, and then a copper plate measuring 3.5 mm in length, 3.5 mm in width, and 1.5 mm in thickness is placed on the conductive paste, and the temperature is raised from 25°C to 175°C over 150 minutes, and then heat-treated at 175°C for 2 hours to obtain a cured sample. The die shear strength between the aluminum plate and the copper plate is measured at room temperature and a shear rate of 500 μm / sec for this cured sample. [8] A conductive paste interposed between the heat dissipation insulating layer and the cooler of a structure having a power semiconductor element, a heat dissipation insulating layer on one side of the power semiconductor element, and a cooler disposed opposite to the other side of the heat dissipation insulating layer, to join them, comprising the following components (A) and (B), and the thermal storage modulus E' of the conductive paste measured at 250°C by the following method 1. 250 A conductive paste having a conductivity of 0.7 GPa or more and 5 GPa or less. (A) Metal particles (B) Thermosetting resin (Method 1) The conductive paste is applied to a glass plate and heated in a nitrogen atmosphere from 30°C to 175°C over 60 minutes, followed by sintering at 175°C for 120 minutes. This yields a cured product with a thickness of 0.05 mm. The storage modulus E' of the obtained cured product at 250°C is measured using a dynamic viscoelasticity analyzer (DMA) at a frequency of 10 Hz. 250[9] The conductive paste according to [8], wherein component (A) comprises spherical silver particles and flaky silver particles, and heat treatment causes component (A) to form a silver particle linkage structure.

[10] The conductive paste according to [8] or [9], wherein component (B) comprises one or more selected from the group consisting of epoxy resin, (meth)acrylic resin, silicone resin, and butadiene rubber.

[11] The conductive paste according to any one of [8] to

[10] , wherein the material of the cooler on the surface facing the heat dissipation insulating layer is copper or aluminum, and the conductive paste is provided in direct contact with the facing surface.

[12] The storage modulus E' of the conductive paste, measured at 25°C by a method similar to method 1. 25 A conductive paste according to any one of [8] to

[11] , wherein the thermal conductivity of the hardened product of the conductive paste is 5 GPa or more and 20 GPa or less.

[13] A conductive paste according to any one of [8] to

[12] , wherein the thermal conductivity of the hardened product of the conductive paste in the thickness direction at 25°C is 10 W / (m·K) or more and 50 W / (m·K) or less, as measured by the following method 2. (Method 2) The conductive paste is applied to a glass plate and heated in a nitrogen atmosphere from 30°C to 175°C over 60 minutes, and then sintered at 175°C for 120 minutes. A hardened product with a thickness of 0.7 mm is obtained. The thermal conductivity λ (W / mK) at 25°C is measured using the laser flash method for the obtained hardened product.

[14] The die shear strength of the Al / heat-treated product of the conductive paste / Cu laminate is 10 N / mm², as measured by the following method 3. 2The conductive paste according to any one of [8] to

[13] as described above. (Method 3) The conductive paste is applied onto an aluminum plate, and then a copper plate having a length of 3.5 mm × a width of 3.5 mm × a thickness of 1.5 mm is placed on the conductive paste, and the temperature is raised from 25°C to 175°C over 150 minutes, and further heat-treated at 175°C for 2 hours to obtain a cured sample. For this cured sample, the die shear strength at room temperature and a shear rate of 500 μm / sec between the aluminum plate and the copper plate is measured.

[15] The conductive paste according to any one of [8] to

[14] , which is used as a non-pressure bonding paste for non-pressure bonding of the heat dissipation insulating layer and the cooler.

[16] A structure in which the heat dissipation insulating layer and the cooler are joined by a cured product of the conductive paste according to any one of [8] to

[15] .

[17] A step of applying the conductive paste according to any one of [8] to

[15] to at least one of the cooler and the heat dissipation insulating layer; and a step of joining the heat dissipation insulating layer and the cooler by arranging the cooler and the heat dissipation insulating layer to face each other through the applied conductive paste and performing heat treatment. A method for manufacturing a structure, including the above steps.

[18] The average particle diameter D of the spherical silver particles 50 is 0.2 μm or more and 15 μm or less, and the power module or conductive paste according to [2] or [9].

[19] The average particle diameter D of the flaky silver particles 50A power module or conductive paste according to any one of [2], [9], and

[18] , wherein the particle size is 3 μm or more and 15 μm or less.

[20] A power module or conductive paste according to any one of [1] to

[15] ,

[18] , and

[19] , wherein the content of component (A) in the conductive paste is 50% by mass or more and 90% by mass or less with respect to the solid content of the conductive paste.

[21] A power module or conductive paste according to any one of [1] to

[15] and

[18] to

[20] , wherein component (B) comprises an epoxy resin and an acrylic resin, for example, a bisphenol-type epoxy resin and ethylene glycol dimethacrylate.

[22] A power module or conductive paste according to any one of [1] to

[15] and

[18] to

[21] , wherein the content of component (B) in the conductive paste is 1% by mass or more and 20% by mass or less with respect to the solid content of the conductive paste.

[23] The power module or conductive paste according to any one of [1] to

[15] and

[18] to

[22] , wherein the conductive paste comprises at least one selected from the group consisting of monomers, resins other than component (B) (e.g., thermoplastic resins), radical polymerization initiators, curing agents, curing accelerators, adhesion aids, coupling agents, solvents, and stress reducers.

[24] The power module or conductive paste according to

[23] , wherein the curing agent is a phenol curing agent, and the content of the curing agent in the conductive paste is 0.01% by mass or more and 10% by mass or less with respect to the entire conductive paste.

[25] The power module or conductive paste according to

[23] or

[24] , wherein the curing accelerator is an imidazole compound, and the content of the curing accelerator in the conductive paste is 0.01% by mass or more and 1% by mass or less with respect to the entire conductive paste.

[26] The power module or conductive paste according to any one of

[23] to

[25] , wherein the adhesion aid is a nitrogen atom-containing compound, for example, a dicyandiamide derivative, and the content of the adhesion aid in the conductive paste is 0.01% by mass or more and 1% by mass or less with respect to the entire conductive paste.

[27] The power module or conductive paste according to any one of

[23] to

[26] , wherein the coupling agent is a silane coupling agent, for example, 3-methacryloxypropyltrimethoxysilane and 3-glycidyloxypropyltrimethoxysilane, and the content of the silane coupling agent in the conductive paste is 0.01% by mass or more and 2% by mass or less with respect to the entire conductive paste.

[28] The power module or conductive paste according to any one of

[23] to

[27] , wherein the solvent is a glycol monomer, for example, ethylene glycol mono-2-ethylhexyl ether and tripropylene glycol mono-n-butyl ether, and the content of the solvent in the conductive paste is 0.1% by mass or more and 3% by mass or less with respect to the entire conductive paste.

[29] The power module or conductive paste according to any one of

[23] to

[28] , wherein the radical polymerization initiator is a peroxide, for example, dicumyl peroxide, and the content of the radical polymerization initiator in the conductive paste is 0.01% by mass or more and 1% by mass or less with respect to the entire conductive paste.

[30] The power module or conductive paste according to any one of [1] to

[15] and

[18] to

[29] , wherein the average linear expansion coefficient CTE1 of the heat-treated conductive paste at a temperature below Tg is 20 ppm / °C or more and 48 ppm / °C or less.

[31] The power module or conductive paste according to

[30] , wherein the average linear expansion coefficient CTE2 of the heat-treated conductive paste at a temperature above Tg is 60 ppm / °C or more and 110 ppm / °C or less.

[32] The power module or conductive paste according to

[31] , wherein the difference between CTE2 and CTE1 (CTE2 - CTE1) is 65 ppm / °C or less.

[33] The power module or conductive paste according to any one of [1] to

[15] and

[18] to

[32] , wherein the glass transition temperature (Tg) of the heat-treated conductive paste is 40°C or higher.

[34] The power module or conductive paste according to any one of [1] to

[15] and

[18] to

[33] , wherein the heat dissipation insulating layer is a resin sheet.

[35] A power module or conductive paste according to any one of [1] to

[15] and

[18] to

[34] , wherein the circuit pattern is a Cu circuit.

[36] A power module or conductive paste according to any one of [1] to

[15] and

[18] to

[35] , wherein the metal plate is a Cu plate or an Al plate.

[37] A power module or conductive paste according to any one of [1] to

[15] and

[18] to

[36] , wherein the thickness of the metal plate is 0.1 mm or more and 20.0 mm or less.

[38] A power module or conductive paste according to any one of [1] to

[15] and

[18] to

[37] , wherein the thickness of the bonding layer is 30 μm or more and 200 μm or less.

[16] A structure in which the heat dissipation insulating layer and the cooler are bonded by a cured product of the conductive paste according to any one of

[18] to

[38] . A method for manufacturing a structure, comprising the steps of: applying a conductive paste according to any one of

[17]

[18] to

[38] to at least one of the cooler and the heat dissipation insulating layer; and joining the heat dissipation insulating layer and the cooler by heat treatment with the cooler and the heat dissipation insulating layer facing each other via the applied conductive paste.

[0007] According to the present invention, it is possible to provide a power module that reduces warping and has excellent adhesion and thermal conductivity between the cooler and adjacent members.

[0008] This is a cross-sectional view showing the configuration of a power module in an embodiment.

[0009] The embodiments will be described below with reference to the drawings. In all drawings, similar components are denoted by the same reference numerals, and their descriptions are omitted where appropriate. Each component can be used individually or in combination of two or more.

[0010] (Power Module) Figure 1 is a cross-sectional view showing an example of the configuration of a power module in this embodiment. The power module 100 shown in Figure 1 includes a heat dissipation insulating layer 101, a metal circuit pattern 103 provided in direct contact with one surface of the heat dissipation insulating layer 101, a power semiconductor element 105 mounted on the circuit pattern 103, a metal plate 107 provided in direct contact with the other surface of the heat dissipation insulating layer 101, a cooler 109 positioned opposite to the back surface of the metal plate 107 opposite to the heat dissipation insulating layer 101, and a bonding layer (first bonding layer 111) that joins the metal plate 107 and the cooler 109. The first bonding layer 111 is formed from a heat-treated conductive paste containing the following components (A) and (B). The thermal storage modulus E' of the conductive paste is measured at 250°C by the following method 1. 250 However, it is between 0.7 GPa and 5 GPa. (A) Metal particles (B) Thermosetting resin (Method 1) A conductive paste is applied to a glass plate and heated from 30°C to 175°C over 60 minutes in a nitrogen atmosphere, followed by sintering at 175°C for 120 minutes. This yields a cured product with a thickness of 0.05 mm. The storage modulus E' at 250°C is measured using a dynamic viscoelasticity analyzer (DMA) at a frequency of 10 Hz for the obtained cured product. 250 Measure (GPa).

[0011] Furthermore, in the power module 100, the metal plate 107, the heat dissipation insulating layer 101, and the circuit pattern 103 constitute a three-layer element mounting substrate 110, and the power semiconductor element 105 is bonded to the upper part of the circuit pattern 103 of the element mounting substrate 110 by a second bonding layer 113. In addition, the circuit pattern 103 and the power semiconductor element 105 are connected by wires 117, and the circuit pattern 103 and the lead frame 115 are bonded by the second bonding layer 113. The entire element mounting surface of the element mounting substrate 110 is sealed with a sealing material 119.

[0012] In this embodiment, the first bonding layer 111 that joins the element mounting substrate 110 on which the power semiconductor element 105 is provided with the cooler 109 is formed from a heat-treated conductive paste containing components (A) and (B), and the thermal storage modulus E' of the conductive paste is also formed. 250This is within a specific range. Therefore, the warping of the element-mounted substrate 110 can be reduced. In addition, the adhesion between the cooler 109, which has a larger bonding surface than the power semiconductor element 105, and the metal plate 107 can be improved, and the thermal conductivity can be improved. Here, in this embodiment, the thermal storage modulus E' of the conductive paste 250 One reason why the warpage of the element-mounted substrate 110 can be reduced when it is within a specific range is the thermal storage modulus E'. 250 By having this within a specific range, the mechanical strength of the first bonding layer 111 can be kept moderately high even at high temperatures, while the warping stress generated at heat can be suitably mitigated. This is thought to reduce warping while ensuring connection reliability. Below, the configuration of the power module 100 will be described in more detail. A more detailed configuration of the conductive paste used in the first bonding layer 111 will be described later.

[0013] The power semiconductor element 105 is, for example, an insulated gate bipolar transistor (IGBT) or a metal oxide semiconductor field effect transistor (MOSFET). An electrode pattern (not shown) is formed on the upper surface of the power semiconductor element 105, and a conductive pattern (not shown) is formed on the lower surface of the power semiconductor element 105. The lower surface of the power semiconductor element 105 is bonded to one side of the circuit pattern 103 via a second junction layer 113. The electrode pattern on the upper surface of the power semiconductor element 105 is electrically connected to the lead frame 115 via wires 117 and the circuit pattern 103. The second junction layer 113 can be, for example, a sintering layer obtained by sintering a known sintering paste.

[0014] The element mounting substrate 110 is a metal circuit board in which a circuit pattern 103 and a metal plate 107 are formed on both sides of a heat dissipation insulating layer 101, preferably a resin substrate in which the heat dissipation insulating layer 101 is made of a resin material. The element mounting substrate 110 receives heat from the power semiconductor element 105 through the circuit pattern 103, transfers the heat to the metal plate 107 which is a heat dissipation means via the heat dissipation insulating layer 101, and dissipates it to the cooler 109. This makes it possible to maintain the insulation of the power module 100 while effectively dissipating the heat generated from the heat-generating power semiconductor element 105 to the cooler 109, thereby improving insulation reliability.

[0015] The planar shape of the heat dissipation insulating layer 101 can be appropriately selected to match the shape of the circuit pattern 103 or the metal plate 107, for example, but it can be rectangular. The thickness of the heat dissipation insulating layer 101 can be, for example, 50 to 250 μm. This improves the mechanical strength of the heat dissipation insulating layer 101, suppresses warping, and improves the heat resistance of the heat dissipation insulating layer 101, while more effectively transferring heat from the circuit pattern 103 to the power semiconductor element 105. It also improves the balance between the heat dissipation and insulation properties of the heat dissipation insulating layer 101. The thermal conductivity of the heat dissipation insulating layer 101 is preferably 10 W / mK (175°C) or higher, more preferably 15 W / mK (175°C) or higher.

[0016] The heat dissipation insulating layer 101 is preferably a resin sheet. Specifically, the resin sheet is formed using a resin composition for sheets. The resin composition for sheets includes, for example, a thermosetting resin such as epoxy resin; a filler such as a thermally conductive filler (e.g., alumina, boron nitride); and a curing agent such as a phenolic resin curing agent. When a thermosetting resin is included, the heat dissipation insulating layer 101 is, for example, a B-staged thermosetting resin. The resin composition for sheets may also further include components such as coupling agents, antioxidants, and leveling agents.

[0017] Specifically, the circuit pattern 103 is a metal circuit board made of a conductive metallic material, preferably a Cu circuit. The Cu circuit is, for example, a circuit board patterned with thick copper (rolled copper). By using thick copper (rolled copper), the resistance value of the circuit pattern 103 can be suitably reduced. At least a portion of the circuit pattern 103 may be covered with a solder resist layer.

[0018] The circuit pattern 103 is formed, for example, by cutting and etching a metal layer (such as thick copper) laminated on the upper surface of a metal plate 107 via a heat dissipation insulating layer 101 into a predetermined pattern. Alternatively, the circuit pattern 103 may be attached to the heat dissipation insulating layer 101 in a state where it has already been processed into a predetermined pattern.

[0019] The thickness of the circuit pattern 103 is, for example, 0.3 mm or more. This further suppresses heat generation of the circuit pattern 103 even in applications requiring high current. Alternatively, the thickness of the circuit pattern 103 can be, for example, 5.0 mm or less, preferably 4.0 mm or less, and even more preferably 3.0 mm or less. This improves circuit processability and allows for a thinner overall substrate 110.

[0020] Examples of metal plates 107 include Cu plates and Al plates. The planar shape and size of the metal plate 107 can be set according to the planar shape and size of the heat dissipation insulating layer 101, for example, and may have the same shape and size as the heat dissipation insulating layer 101. The thickness of the metal plate 107 is, for example, 0.1 mm or more, preferably 0.5 mm or more, and more preferably 1.0 mm or more. This makes it possible to suppress warping of the element mounting substrate 110 while improving the heat dissipation performance of the element mounting substrate 110. Furthermore, the thickness of the metal plate 107 is preferably 20.0 mm or less, more preferably 5.0 mm or less. This improves processability and makes the entire element mounting substrate 110 thinner.

[0021] The lead frame 115 supports and fixes the power semiconductor device 105 and makes an electrical connection with external wiring. It may be obtained, for example, by press working or etching a thin plate of a metal material such as Cu or Fd. Also, the wire 117 can be made of a metal material such as Cu, Al, or Ag, for example.

[0022] The encapsulant 119 seals the element mounting surface of the element mounting substrate 110. In the example of FIG. 1, the encapsulant 119 seals the heat dissipation insulating layer 101 and the entire member on the element side from this, and electrical conduction with the outside of the power module 100 is ensured at the end of the lead frame 115.

[0023] The encapsulant 119 is, for example, a cured body of an encapsulating resin composition. The encapsulating resin composition may contain, for example, a thermosetting resin such as an epoxy resin; an inorganic filler such as silica; a curing agent such as a phenolic resin curing agent; a curing accelerator, etc. Also, the encapsulating resin composition may further contain various additives such as a coloring agent, a mold release agent, an ion scavenger, a low stress agent, a flame retardant, an antioxidant, etc.

[0024] The cooler 109 is provided facing the metal plate 107 of the element mounting substrate 110 and is joined by the first bonding layer 111. The material of the cooler 109 on the facing surface with the heat dissipation insulating layer 101 is preferably copper or aluminum, and the conductive paste (first bonding layer 111) is provided in direct contact with the facing surface. Thereby, the adhesion between the cooler 109 and the metal plate 107 can be more stably improved.

[0025] Hereinafter, the configuration of the conductive paste for forming the first bonding layer 111 will be described more specifically. [[ID=!4]]

[0026] (Conductive Paste) The conductive paste is a conductive paste that intervenes between the heat dissipation insulating layer 101 and the cooler 109 of a structure having the power semiconductor device 105, the heat dissipation insulating layer 101 provided on one surface of the power semiconductor device 105, and the cooler 109 disposed facing the other surface of the heat dissipation insulating layer 101, and joins these. It contains the above-described components (A) and (B), and the storage elastic modulus in heat E' measured at 250°C by Method 1 250is 0.7 GPa or more and 5 GPa or less. More specifically, the conductive paste joins the element mounting substrate 110 and the cooler 109, and preferably directly joins the metal plate 107 and the cooler 109.

[0027] (Storage Elastic Modulus) The storage elastic modulus E' of the conductive paste during heating 250 is 0.7 GPa or more, preferably 1.0 GPa or more, and more preferably 2.0 GPa or more. Thereby, good adhesion strength can be exhibited. The storage elastic modulus E' during heating 250 If it is too low, there is a concern that the mechanical strength and adhesion strength of the first bonding layer 111 at high temperatures may decrease. Also, in terms of relaxation of the warping stress generated during heating, the storage elastic modulus E' of the conductive paste 250 is 5 GPa or less, preferably 4.5 GPa or less, more preferably 4.0 GPa or less, and even more preferably 3.0 GPa or less. Also, since the first bonding layer 111 has appropriate flexibility even at high temperatures, during the manufacture or driving of the power module 100, the thermal stress generated due to the difference in the linear expansion coefficient between the cooler 109 and the metal plate 107 or the heat dissipation insulating layer 101 can be preferably relaxed to reduce the residual stress inside the structure, and the occurrence of warping of the entire power module 100 can be more stably suppressed.

[0028] Here, the storage elastic modulus E' of the conductive paste during heating 250 is measured by the aforementioned method 1. That is, the conductive paste is applied on a glass plate, heated from 30 °C to 175 °C over 60 minutes in a nitrogen atmosphere, and then sintered at 175 °C for 120 minutes. Thereby, a cured product with a thickness of 0.05 mm is obtained. For the obtained cured product, the storage elastic modulus at 250 °C is measured using a dynamic viscoelasticity measuring device (DMA) at a frequency of 10 Hz.

[0029] The storage elastic modulus E' of the conductive paste measured at 25 °C by a method according to method 1 25The storage modulus E' of the conductive paste is preferably 5 GPa or higher, more preferably 7 GPa or higher, even more preferably 8 GPa or higher, and even more preferably 12 GPa or higher. This allows for even better adhesion strength. Furthermore, from the viewpoint of obtaining the effects of warping stress relaxation and crack suppression more stably, the storage modulus E' of the conductive paste is 25 The pressure is preferably 20 GPa or less, more preferably 18 GPa or less, and even more preferably 16 GPa or less.

[0030] (Thermal Conductivity) The thermal conductivity of the conductive paste in the thickness direction at 25°C, as measured by the following method 2, is preferably 10 W / (m·K) or higher, more preferably 15 W / (m·K) or higher, and even more preferably 20 W / (m·K) or higher. This allows for more efficient heat dissipation. The above thermal conductivity may also be, for example, 50 W / (m·K) or lower.

[0031] (Method 2) A conductive paste is applied to a glass plate and heated from 30°C to 175°C over 60 minutes in a nitrogen atmosphere, followed by sintering at 175°C for 120 minutes. This yields a hardened material with a thickness of 0.7 mm. The thermal conductivity λ (W / mK) of the obtained hardened material at 25°C is measured using the laser flash method.

[0032] (Die Shear Strength) The die shear strength of the Al / conductive paste heat-treated product / Cu laminate, measured by the following method 3, is preferably 10 N / mm 2 The above is preferable, with a load of 15 N / mm². 2 More preferably 20 N / mm 2 This completes the process. This further improves the adhesion between the metal plate 107 and the cooler 109, thereby suppressing delamination. Furthermore, the die shear strength is, for example, 50 N / mm². 2 The following is also acceptable.

[0033] (Method 3) A conductive paste is applied to an aluminum plate, and then a copper plate measuring 3.5 mm in length, 3.5 mm in width, and 1.5 mm in thickness is placed on the conductive paste. The temperature is raised from 25°C to 175°C over 150 minutes, and then heat-treated at 175°C for 2 hours to obtain a cured sample. The die shear strength of this cured sample between the aluminum plate and the copper plate at room temperature and a shear rate of 500 μm / sec is measured, for example, using a Dage4000 (Nordson Advanced Technologies). Here, room temperature is specifically 25°C.

[0034] (Glass transition temperature (Tg), coefficient of linear expansion (CTE1 and CTE2)) The Tg of the heat-treated conductive paste, measured by the following method, is preferably 40°C or higher, more preferably 60°C or higher, and may also be, for example, 120°C or lower. This allows for obtaining desirable heat resistance.

[0035] The average linear expansion coefficient CTE1 of the heat-treated conductive paste at temperatures below Tg, as measured by the following method, is preferably 20 ppm / °C or higher, more preferably 35 ppm / °C or higher, and also preferably 48 ppm / °C or lower, and more preferably 43 ppm / °C or lower. This allows for more favorable adhesion. The average linear expansion coefficient CTE2 of the heat-treated conductive paste at temperatures above Tg, as measured by the following method, is preferably 60 ppm / °C or higher, more preferably 70 ppm / °C or higher, also preferably 110 ppm / °C or lower, and more preferably 100 ppm / °C or lower. This allows for more favorable adhesion.

[0036] Furthermore, the difference between CTE2 and CTE1 (CTE2-CTE1) is preferably 65 ppm / °C or less, more preferably 60 ppm / °C or less, even more preferably 55 ppm / °C or less, and may also be, for example, 10 ppm / °C or more. This effectively relieves thermal stress caused by the difference in linear expansion coefficients between members during the manufacturing process and thermal cycles during operation of the power module 100, thereby more stably reducing the occurrence of warping.

[0037] Tg and the coefficient of linear expansion are specifically measured by the following method. A conductive paste is applied to a mold measuring 4 mm in length, 10 mm in width, and 0.15 mm in thickness. The mold is heated at a constant rate from 30°C to 200°C over 60 minutes, and then heated at 200°C for 120 minutes to prepare a test specimen. Then, using a thermomechanical analyzer, the obtained test specimen is pulled with a load of 10 mN while the temperature is increased from -100°C to 330°C at a heating rate of 5°C / min. The amount of expansion of the test specimen with respect to temperature is detected as an electrical output by a differential transformer, and a graph showing the amount of expansion of the test specimen with respect to temperature is created. Tg is then determined from the inflection point of the graph. In addition, the average coefficient of linear expansion CTE2 (ppm / °C) at temperatures above the calculated Tg and the average coefficient of linear expansion CTE1 (ppm / °C) at temperatures below Tg are measured. Examples of thermomechanical analyzers used to measure Tg and the mean linear expansion coefficient include the TMA / SS6100 manufactured by Seiko Instruments Corporation. Next, the components of the conductive paste will be explained.

[0038] (Component (A)) Component (A) is a metal particle, and specifically contains at least one selected from the group consisting of silver particles, copper particles, and gold particles as the main component, and preferably contains silver particles. This makes the first bonding layer 111 even more resistant. The purity of the main component of component (A) is preferably 95% by mass or more, more preferably 98% by mass or more, even more preferably 99% by mass or more, and specifically 100% by mass or less. Component (A) may contain impurities that are inevitably mixed in during the manufacturing process.

[0039] The shape of component (A) can be one or more shapes selected from the group consisting of, for example, spherical, polygonal (including approximately spherical with rounded corners), flake-like, dendritic, and scaly.

[0040] Furthermore, component (A) preferably contains spherical silver particles and flaky silver particles, and heat treatment causes component (A) to form a silver particle linkage structure. This allows for more favorable adhesion and thermal conductivity in the joining of the cooler 109 and the metal plate 107. Here, the silver particle linkage structure specifically refers to a structure in which silver particles collide with each other and the interface disappears. In this embodiment, the thermal storage modulus E' 250 Because it is within a specific range, the metal particle linkage structure can be stably maintained and functioned as a framework even at high temperatures, resulting in more favorable heat dissipation and conductivity.

[0041] Of these, the average particle size D of the spherical silver particles 50 The particle size is preferably 0.2 μm or larger, more preferably 0.4 μm or larger, and even more preferably 0.6 μm or larger. This suppresses excessive thixotropy when using the conductive paste. Also, the average particle size D of the spherical silver particles. 50 The thickness is preferably 15 μm or less, more preferably 12 μm or less, and even more preferably 8 μm or less. This makes it possible to more stably improve the adhesion between the metal plate 107 and the cooler 109.

[0042] Also, the average particle size D of the flaky silver particles 50 The particle size is preferably 3 μm or larger, more preferably 4 μm or larger, and even more preferably 5 μm or larger. This allows for easy formation of a network after sintering of the conductive paste, further improving heat dissipation. Also, the average particle size D of the flaky silver particles. 50 The thickness is preferably 15 μm or less, more preferably 12 μm or less, and even more preferably 8 μm or less. This makes it possible to more stably improve the adhesion between the metal plate 107 and the cooler 109.

[0043] Here, the average particle size D of component (A) 50 Specifically, this can be measured using a commercially available laser-type particle size analyzer (for example, the SALD-7000 manufactured by Shimadzu Corporation).

[0044] The content of spherical silver particles in the conductive paste is preferably 40% by mass or more, more preferably 50% by mass or more, preferably 80% by mass or less, and more preferably 70% by mass or less, relative to the solid content of the conductive paste. This allows for a more favorable balance of effects on warp reduction, adhesion, and thermal conductivity. Similarly, the content of flake-like silver particles in the conductive paste is preferably 10% by mass or more, more preferably 20% by mass or more, preferably 50% by mass or less, and more preferably 40% by mass or less, relative to the solid content of the conductive paste.

[0045] The content of component (A) in the conductive paste is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, and even more preferably 82% by mass or more, relative to the solid content of the conductive paste. This allows for the formation of a more favorable bonding structure of component (A) even when the interparticle attractive force of component (A) is small. Furthermore, the content of component (A) in the conductive paste is preferably 90% by mass or less, more preferably 87% by mass or less, relative to the solid content of the conductive paste. This improves the dispersibility of component (B) at the particle interface of component (A).

[0046] Here, the solid content of the conductive paste refers to the non-volatile components in the conductive paste, which is the remainder after removing volatile components such as water and solvents.

[0047] (Component (B)) Component (B) is a thermosetting resin. The thermosetting resin may be an oligomer or a polymer. Examples of component (B) include one or more selected from the group consisting of epoxy resin, (meth)acrylic resin, silicone resin, butadiene rubber, phenolic resin, resin having a benzoxazine ring, melamine resin, unsaturated polyester resin, maleimide resin, polyurethane resin, diallyl phthalate resin, and cyanate resin. Component (B) preferably includes one or more selected from the group consisting of epoxy resin, (meth)acrylic resin, silicone resin, and butadiene rubber, and more preferably includes epoxy resin and acrylic resin. This allows for better adhesion strength.

[0048] As the epoxy resin, for example, a liquid epoxy resin having two or more epoxy groups in one molecule can be used. Specifically, the epoxy resin is one or more selected from the group consisting of trisphenolmethane type epoxy resin; hydrogenated bisphenol A type liquid epoxy resin; bisphenol F type liquid epoxy resin such as bisphenol-F-diglycidyl ether; and orthocresol novolac type epoxy resin. Among the above specific examples, it is preferable that the epoxy resin contains hydrogenated bisphenol A type liquid epoxy resin or bisphenol F type liquid epoxy resin, and more preferably bisphenol F type liquid epoxy resin. This improves the handling properties of the conductive paste and allows for uniform application of the conductive paste, thereby improving reliability. Furthermore, it is preferable from the viewpoint that the conductive paste can be suitably cured and shrunk, thereby forming an appropriate linkage structure of component (A) and improving heat dissipation. In addition, it is preferable from the viewpoint that the epoxy resin remains and is dispersed suitably at the particle interface of component (A).

[0049] ((meth)acrylic resin) As the (meth)acrylic resin, a liquid having two or more (meth)acrylic groups in one molecule can be used. Specifically as the (meth)acrylic resin, a polymer or copolymer of the (meth)acrylic monomer described below can be used. Here, the polymerization or copolymerization method is not limited, and known methods using general polymerization initiators and chain transfer agents, such as solution polymerization, can be used.

[0050] In this specification, (meth)acrylic resin refers to acrylic resin and methacrylic resin, and (meth)acrylate refers to acrylate and methacrylate. Methacrylic acid refers to acrylic acid and methacrylic acid. (Meth)acryloyl refers to acryloyl and methacryloyl.

[0051] (Silicone resin) Examples of silicone resins include one or more selected from the group consisting of methyl silicone resin, methylphenyl silicone resin, phenyl silicone resin, alkyd-modified silicone resin, polyester-modified silicone resin, urethane-modified silicone resin, epoxy-modified silicone resin, and acrylic-modified silicone resin.

[0052] (Butadiene rubber) Examples of butadiene rubber include one or more selected from the group consisting of butadiene rubber, polybutadiene rubber, and styrene-butadiene rubber.

[0053] The content of component (B) in the conductive paste is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, relative to the solid content of the conductive paste. This allows for the formation of a linking structure of component (A) while exhibiting suitable adhesion to the adherend. Alternatively, the content of component (B) in the conductive paste is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 14% by mass or less, relative to the solid content of the conductive paste. This allows for the formation of a linking structure of component (A) more efficiently.

[0054] Furthermore, the conductive paste may contain components other than components (A) and (B). Examples of such components include monomers, resins other than component (B) (e.g., thermoplastic resins), radical polymerization initiators, curing agents, curing accelerators, adhesion aids, coupling agents, solvents, stress reducers, and the like.

[0055] (Monomer) Examples of monomers include one or more selected from the group consisting of acrylic monomers, epoxy monomers, and maleimide monomers. The monomer may be a monomer that is a constituent unit of component (B), and may be at least one of epoxy monomers and acrylic monomers. When the conductive paste contains epoxy monomer as a monomer, the conductive paste preferably further contains a curing agent. When the conductive paste contains acrylic monomer as a monomer, the conductive paste preferably further contains a radical polymerization initiator.

[0056] (Epoxy Monomers) Epoxy monomers are compounds that have epoxy groups in their structure. Epoxy monomers may be monofunctional epoxy monomers having only one epoxy group in their structure, or they may be polyfunctional epoxy monomers having two or more epoxy groups in their structure.

[0057] Specifically, monofunctional epoxy monomers are one or more monomers selected from the group consisting of 4-tert-butylphenylglycidyl ether, m-cresylglycidyl ether, p-cresylglycidyl ether, phenylglycidyl ether, and cresylglycidyl ether.

[0058] Specifically, polyfunctional epoxy monomers are one or more monomers selected from the group consisting of: bisphenol compounds such as bisphenol A, bisphenol F, and biphenol, or derivatives thereof; diols having an alicyclic structure such as hydrogenated bisphenol A, hydrogenated bisphenol F, hydrogenated biphenol, cyclohexanediol, cyclohexanedimethanol, and cyclohexanediethanol, or derivatives thereof; bifunctional compounds obtained by epoxidizing aliphatic diols such as butanediol, hexanediol, octanediol, nonanediol, and decanediol, or derivatives thereof; trifunctional compounds having a trihydroxyphenylmethane skeleton or an aminophenol skeleton; and polyfunctional compounds obtained by epoxidizing phenol novolac resin, cresol novolac resin, phenol aralkyl resin, biphenyl aralkyl resin, naphthol aralkyl resin, etc.

[0059] ((meth)acrylic monomer) A (meth)acrylic monomer is a monomer that has a (meth)acrylic group in its structure. Here, the (meth)acrylic group refers to an acrylic group and a methacrylic group (methacrylate group). A (meth)acrylic monomer may be a monofunctional (meth)acrylic monomer having only one (meth)acrylic group in its structure, or a polyfunctional (meth)acrylic monomer having two or more (meth)acrylic groups in its structure. In this embodiment, the (meth)acrylic group includes a (meth)acrylate group.

[0060] Monofunctional (meth)acrylic monomers include, specifically, 2-phenoxyethyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, isoamyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isodecyl (meth)acrylate, n-lauryl (meth)acrylate, n-tridecyl (meth)acrylate, n-stearyl (meth)acrylate, isostearyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, butoxydiethylene glycol (meth)acrylate, methoxytriethylene glycol (meth)acrylate, 2-ethylhexyldiethylene glycol (meth)acrylate, and methoxypolyethylene glycol. (meth)acrylate, methoxydipropylene glycol (meth)acrylate, cyclohexyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, nonylphenol ethylene oxide modified (meth)acrylate, phenylphenol ethylene oxide modified (meth)acrylate, isobornyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate quaternary, glycidyl (meth)acrylate, neopentyl glycol (meth)acrylate benzoate, 1,It is one or more monomers selected from the group consisting of 4-cyclohexanedimethanol mono(meth)acrylate, 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate, 2-hydroxy-3-phenoxypropyl(meth)acrylate, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalic acid, 2-(meth)acryloyloxyethyl acid phosphate, and 2-(meth)acryloyloxyethyl acid phosphate.

[0061] Polyfunctional acrylic monomers include, specifically, ethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, propoxylated bisphenol A di(meth)acrylate, hexane-1,6-diol bis(2-methyl(meth)acrylate), 4,4'-isopropylidene diphenol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,6-bis((meth)acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane, 1,4 It is one or more monomers selected from the group consisting of -bis((meth)acryloyloxy)butane, 1,6-bis((meth)acryloyloxy)hexane, triethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, N,N'-di(meth)acryloylethylenediamine, N,N'-(1,2-dihydroxyethylene)bis(meth)acrylamide, and 1,4-bis((meth)acryloyl)piperazine.

[0062] The monomer content in the conductive paste can be, for example, 0.1% to 10% by mass, preferably 1 to 6% by mass, relative to the total conductive paste.

[0063] (Radical polymerization initiator) The radical polymerization initiator is, for example, at least one selected from the group consisting of azo compounds and peroxides, and is preferably a peroxide.

[0064] Peroxides include, for example, bis(1-phenyl-1-methylethyl)peroxide, 1,1-bis(1,1-dimethylethylperoxy)cyclohexane, methyl ethyl ketone peroxide, cyclohexane peroxide, acetylacetone peroxide, 1,1-di(tert-hexylperoxy)cyclohexane, 1,1-di(tert-butylperoxy)-2-methylcyclohexane, 1,1-di(tert-butylperoxy)cyclohexane, and 2,2-di(tert-butylperoxy)buta n-butyl-4,4-di(tert-butylperoxy)valerate, 2,2-di(4,4-di(tert-butylperoxy)cyclohexane)propane, p-methane hydroperoxide, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, tert-butyl hydroperoxide, di(2-tert-butylperoxyisopropyl)benzene, dicumyl peroxide, 2,5-dimethyl-2,5-di(te rt-butylperoxy)hexane, tert-butylcumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexine, diisobutyl peroxide, di(3,5,5-trimethylhexanoyl) peroxide, dilauryl peroxide, di(3-methylbenzoyl) peroxide, benzoyl(3-methylbenzoyl) peroxide, dibenzoyl peroxide, di(4-methylbenzoyl) peroxide, din-propyl Peroxydicarbonate, diisopropyl peroxydicarbonate, di(2-ethylhexyl) peroxydicarbonate, disec-butyl peroxydicarbonate, cumyl peroxyneodecanate, 1,1,3,3-tetramethylbutyl peroxyneodecanate, tert-hexylneodecanate, tert-butyl peroxyneoheptanate, tert-hexyl peroxypivarate, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanate, 2,5-dimethyl-2,It is one or more compounds selected from the group consisting of 5-di(2-diethylhexanoylperoxy)hexane, tert-butylperoxy-2-ethylhexanate, tert-hexylperoxyisopropyl monocarbonate, tert-butylperoxymaleic acid, tert-butylperoxy-3,5,5-trimethylhexanate, tert-butylperoxyisopropyl monocarbonate, tert-butylperoxy-2-ethylhexyl monocarbonate, tert-hexylperoxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, tert-butylperoxyacetonate, tert-peroxy-3-methylbenzoate, tert-butylperoxybenzoate, tert-butylperoxyallyl monocarbonate, and 3,3',4,4'-tetra(tert-butylperoxycarbonyl)benzophenone.

[0065] The content of the radical polymerization initiator in the conductive paste is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and preferably 1% by mass or less, and more preferably 0.5% by mass or less, relative to the total content of the conductive paste. This makes the curing properties of the conductive paste more favorable.

[0066] (Curing agent) Examples of curing agents include phenol curing agents. Phenol curing agents are selected from the group consisting of, for example, novolac-type phenolic resins such as phenol novolac resin, cresol novolac resin, bisphenol novolac resin, and phenol-biphenyl novolac resin; polyvinylphenol; polyfunctional phenolic resins such as triphenylmethane-type phenolic resin; modified phenolic resins such as terpene-modified phenolic resin and dicyclopentadiene-modified phenolic resin; phenol aralkyl-type phenolic resins such as phenol aralkyl resin having at least one of a phenylene skeleton and a biphenylene skeleton, and naphthol aralkyl resin having at least one of a phenylene and biphenylene skeleton; bisphenol compounds such as bisphenol A and bisphenol F (dihydroxydiphenylmethane); and compounds having a biphenylene skeleton such as 4,4'-biphenol, with bisphenol compounds being preferred and bisphenol F being more preferred. This makes it possible to form a metal particle linkage structure more stably with more favorable curing shrinkage characteristics of the epoxy resin.

[0067] The content of the curing agent in the conductive paste is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, even more preferably 1% by mass or more, and preferably 10% by mass or less, and even more preferably 6% by mass or less, relative to the total content of the conductive paste. This makes the curing properties of the conductive paste more favorable.

[0068] (Curing accelerator) The curing accelerator is one or more selected from the group consisting of, for example, imidazole compounds; phosphorus atom-containing compounds such as organophosphines, tetrasubstituted phosphonium compounds, phosphobetaine compounds, adducts of phosphine compounds and quinone compounds, and adducts of phosphonium compounds and silane compounds; and nitrogen atom-containing compounds such as dicyandiamide, 1,8-diazabicyclo[5.4.0]undecene-7, benzyldimethylamine, amidines and tertiary amines, and quaternary ammonium salts of the above amidines or tertiary amines, and is preferably an imidazole compound.

[0069] The imidazole compounds are, for example, one or more compounds selected from the group consisting of 2-phenyl-1H-imidazole-4,5-dimethanol, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-methylimidazole, 2-phenylimidazole, 2,4-diamino-6-[2-methylimidazolyl-(1)]-ethyl-s-triazine, 2-undecylimidazole, 2-heptadecylimidazole, 2,4-diamino-6-[2-methylimidazolyl-(1)]-ethyl-s-triazine isocyanurate adduct, 2-phenylimidazole isocyanurate adduct, 2-methylimidazole isocyanurate adduct, 1-cyanoethyl-2-phenylimidazolium trimellitate, and 1-cyanoethyl-2-undecylimidazolium trimellitate.

[0070] The content of the curing accelerator in the conductive paste is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and preferably 1% by mass or less, and more preferably 0.5% by mass or less, relative to the total amount of the conductive paste. This makes the curing characteristics of the conductive paste more favorable.

[0071] (Adhesion aids) Examples of adhesion aids include nitrogen atom-containing compounds such as dicyandiamide, as mentioned in the section on curing accelerators.

[0072] The content of the adhesion aid in the conductive paste is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and preferably 1% by mass or less, and more preferably 0.5% by mass or less, relative to the total conductive paste. This makes it possible to improve the adhesion between the cooler and the adjacent member.

[0073] (Coupling Agents) Examples of coupling agents include silane coupling agents. Examples of silane coupling agents include vinylsilanes such as vinyltrimethoxysilane and vinyltriethoxysilane; epoxysilanes such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane; styrylsilanes such as p-styryltrimethoxysilane; methacrylsilanes such as 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane; acrylicsilanes such as 3-(trimethoxysilyl)propyl methacrylate and 3-acryloxypropyltrimethoxysilane; and N-2-(A One or more selected from the group consisting of aminosilanes such as (minoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, and N-phenyl-γ-aminopropyltrimethoxysilane; isocyanurate silanes; alkyl silanes; ureidosilanes such as 3-ureidopropyltrialkoxysilane; mercaptosilanes such as 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane; and isocyanate silanes such as 3-isocyanatetopropyltriethoxysilane, preferably at least one of epoxysilane and methacrylicsilane, more preferably epoxysilane and methacrylicsilane.

[0074] The coupling agent content in the conductive paste is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, preferably 2% by mass or less, and more preferably 1% by mass or less, relative to the total conductive paste. This makes it possible to improve the adhesion between the cooler and the adjacent member.

[0075] (Solvent) Examples of solvents include reactive diluents having reactive groups that are involved in the crosslinking reaction of the binder resin contained in the conductive paste, such as component (B). Examples of reactive diluents include the aforementioned acrylic monomers, epoxy monomers, and maleimide monomers, as well as glycol monomers.

[0076] Glycol monomers include, for example, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-propyl ether, ethylene glycol monoisopropyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol monoisobutyl ether, ethylene glycol monohexyl ether, ethylene glycol mono-2-ethylhexyl ether, ethylene glycol monoallyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, diethylene glycol monoisopropyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol monoisobutyl ether, diethylene glycol monohexyl ether, diethylene glycol mono-2-ethylhexyl ether, diethylene glycol monobenzyl ether, triethylene glycol, triethylene glycol It is one or more selected from the group consisting of tripropylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol mono-n-butyl ether, tetraethylene glycol, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, tetraethylene glycol mono-n-butyl ether, propylene glycol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, propylene glycol monoisopropyl ether, propylene glycol mono-n-butyl ether, propylene glycol monophenyl ether, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-n-butyl ether, tripropylene glycol, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, and tripropylene glycol mono-n-butyl ether.

[0077] The content of the reactive diluent in the conductive paste is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, preferably 3% by mass or less, and more preferably 1.5% by mass or less, relative to the total amount of the conductive paste. This makes the curing characteristics of the conductive paste more favorable.

[0078] Furthermore, the solvent may include a non-reactive solvent that does not have reactive groups that participate in the crosslinking reaction of the binder resin.

[0079] (Low-stress agent) The low-stress agent is one or more selected from the group consisting of, for example, silicone compounds such as silicone oil and silicone rubber; polybutadiene compounds such as polybutadiene maleic anhydride adducts; and acrylonitrile butadiene copolymer compounds. The content of the low-stress agent in the conductive paste can be, for example, 0.01 to 1% by mass relative to the total conductive paste.

[0080] Next, a method for manufacturing conductive paste will be described. Conductive paste can be obtained by a method that includes, for example, a mixing step of preparing a mixture by mixing raw material components including components (A) and (B), and a degassing step of removing air contained in the mixture. In the mixing step, the raw material components are mixed to prepare a mixture. For example, a three-roll mixer or the like can be used as a mixing method. Alternatively, after pre-mixing each component, kneading may be performed using a three-roll mixer or the like. In this case, the long-term workability of the conductive paste can be improved by appropriately adjusting the preparation conditions, for example, by performing the pre-mixing under reduced pressure. In the degassing step, air contained in the mixture is removed. For example, the air contained in the mixture can be removed by letting the mixture stand under vacuum.

[0081] Here, the components (A) and (B) are included, and the thermal storage modulus E' 250To obtain a conductive paste with a specific conductivity range, it is important to appropriately select the components and their proportions contained in the conductive paste, as well as the preparation process for the conductive paste. For example, it is important to design the formulation by appropriately selecting and combining the material, shape, size, and amount of component (A) and the type and amount of component (B) contained in the conductive paste. It is preferable to use a combination of spherical silver particles and flaky silver particles, and it is more preferable to keep their sizes within the aforementioned range. It is also preferable to keep the amounts of components (A) and (B) within the aforementioned range.

[0082] The conductive paste obtained in this embodiment is suitably used for forming the first bonding layer 111 in the power module 100. In this case, the conductive paste is preferably used as a pressureless bonding paste to bond the heat dissipation insulating layer 101 (element mounting substrate 110) and the cooler 109 without pressure. This simplifies the bonding process. The thickness of the first bonding layer 111 is, for example, 30 μm or more, preferably 40 μm or more, and also, for example, 200 μm or less, preferably 100 μm or less. Furthermore, the conductive paste obtained in this embodiment may be used in the following structures.

[0083] (Structure) In this embodiment, the heat dissipation insulating layer 101 and the cooler 109 are joined by the cured conductive paste. This reduces warping of the structure and provides excellent adhesion and thermal conductivity between the cooler 109 and the heat dissipation insulating layer 101. The heat dissipation insulating layer 101 may be in direct contact with the cured conductive paste, or there may be an intervening member between the heat dissipation insulating layer 101 and the cured conductive paste. For example, the heat dissipation insulating layer 101 may be a component of the element mounting substrate 110 described above. In this case, the structure may further have a metal plate 107 on the outside of the heat dissipation insulating layer 101, and the metal plate 107 and the cooler 109 are joined by the cured conductive paste.

[0084] Such a structure can be obtained, for example, by a manufacturing method that includes the steps of: applying a conductive paste to at least one of the cooler 109 and the heat dissipation insulating layer 101; and joining the heat dissipation insulating layer 101 and the cooler 109 by heat treatment with the cooler 109 and the heat dissipation insulating layer 101 facing each other via the applied conductive paste. Alternatively, the conductive paste may be applied to at least one of the cooler 109 and the element mounting substrate 110. For example, the structure can be obtained by a manufacturing method that includes the steps of: applying a conductive paste to at least one of the cooler 109 and the metal plate 107; and joining the metal plate 107 and the cooler 109 by heat treatment with the cooler 109 and the metal plate 107 facing each other via the applied conductive paste.

[0085] Furthermore, the manufacturing method of the power module 100 may include, for example, the manufacturing method of the structure described above. For example, the power module 100 may include the steps of: preparing a structure by bonding power semiconductor elements 105 to predetermined positions on the circuit pattern 103 of the element mounting substrate 110 with a second bonding layer 113, arranging a lead frame 115 and the second bonding layer 113, and sealing it with a sealing material 119; and forming a first bonding layer 111 by applying the conductive paste of this embodiment between the metal plate 107 of the structure and the cooler 109 and performing heat treatment.

[0086] The present invention has been described above based on embodiments, but the present invention is not limited to the above embodiments, and its configuration can be changed without changing the gist of the present invention. Examples of reference embodiments are given below. 1. A heat dissipation insulating layer; a metal circuit pattern provided in direct contact with one surface of the heat dissipation insulating layer; a power semiconductor element mounted on the circuit pattern; a metal plate provided in direct contact with the other surface of the heat dissipation insulating layer; a cooler positioned opposite to the back surface of the metal plate opposite to the heat dissipation insulating layer; and a bonding layer joining the metal plate and the cooler, wherein the bonding layer is formed from a heat-treated conductive paste containing the following components (A) and (B), and the thermal storage modulus E' of the conductive paste is measured at 250°C by the following method 1.250 However, the power module has a pressure of 0.7 GPa or more and 5 GPa or less. (A) Metal particles (B) Thermosetting resin (Method 1) The conductive paste is applied to a glass plate and heated in a nitrogen atmosphere from 30°C to 175°C over 60 minutes, and then sintered at 175°C for 120 minutes. This yields a cured product with a thickness of 0.05 mm. The storage modulus E' of the obtained cured product at 250°C is measured using a dynamic viscoelasticity analyzer (DMA) at a frequency of 10 Hz. 250 1. Measure the (GPa). 2. The power module according to 1, wherein component (A) comprises spherical silver particles and flaky silver particles, and component (A) forms a silver particle linkage structure by heat treatment. 3. The power module according to 1 or 2, wherein component (B) comprises one or more selected from the group consisting of epoxy resin, (meth)acrylic resin, silicone resin, and butadiene rubber. 4. The power module according to 1 or 2, wherein the material of the cooler on the surface facing the heat dissipation insulating layer is copper or aluminum, and the bonding layer is provided in direct contact with the facing surface. 5. The storage modulus E' of the conductive paste, measured at 25°C by a method similar to method 1. 25 However, the power module described in 1. or 2. is 5 GPa or more and 20 GPa or less. 6. The power module described in 1. or 2. is 10 W / (m·K) or more and 50 W / (m·K) or less in the thickness direction at 25°C, as measured by the following method 2. (Method 2) The conductive paste is applied to a glass plate and heated from 30°C to 175°C over 60 minutes in a nitrogen atmosphere, followed by sintering at 175°C for 120 minutes. This yields a cured material with a thickness of 0.7 mm. The thermal conductivity λ (W / mK) at 25°C is measured using the laser flash method for the obtained cured material. 7. The die shear strength of the Al / heat-treated material of the conductive paste / Cu laminate is 10 N / mm², as measured by the following method 3. 2The power module described in 1. or 2. above. (Method 3) The conductive paste is applied to an aluminum plate, and then a copper plate measuring 3.5 mm in length, 3.5 mm in width, and 1.5 mm in thickness is placed on the conductive paste, and the temperature is raised from 25°C to 175°C over 150 minutes, and then heat-treated at 175°C for 2 hours to obtain a cured sample. The die shear strength between the aluminum plate and the copper plate is measured at room temperature and a shear rate of 500 μm / sec for this cured sample. 8. A conductive paste interposed between the heat dissipation insulating layer and the cooler of a structure having a power semiconductor element, a heat dissipation insulating layer on one side of the power semiconductor element, and a cooler disposed opposite to the other side of the heat dissipation insulating layer, to join them, comprising the following components (A) and (B), and the thermal storage modulus E' of the conductive paste measured at 250°C by Method 1 below. 250 A conductive paste having a conductivity of 0.7 GPa or more and 5 GPa or less. (A) Metal particles (B) Thermosetting resin (Method 1) The conductive paste is applied to a glass plate and heated in a nitrogen atmosphere from 30°C to 175°C over 60 minutes, followed by sintering at 175°C for 120 minutes. This yields a cured product with a thickness of 0.05 mm. The storage modulus E' of the obtained cured product at 250°C is measured using a dynamic viscoelasticity analyzer (DMA) at a frequency of 10 Hz. 250 (GPa) is measured. 9. The conductive paste according to 8, wherein component (A) comprises spherical silver particles and flaky silver particles, and component (A) forms a silver particle linkage structure by heat treatment. 10. The conductive paste according to 8, wherein component (B) comprises one or more selected from the group consisting of epoxy resin, (meth)acrylic resin, silicone resin, and butadiene rubber. 11. The conductive paste according to 8, wherein the material of the cooler on the surface facing the heat dissipation insulating layer is copper or aluminum, and the conductive paste is provided in direct contact with the facing surface. 12. The storage modulus E' of the conductive paste, measured at 25°C by a method similar to method 1. 25A conductive paste as described in 8, wherein the thermal conductivity is 5 GPa or more and 20 GPa or less. 13. A conductive paste as described in 8, wherein the thermal conductivity of the cured product of the conductive paste, measured by the following method 2, is 10 W / (m·K) or more and 50 W / (m·K) or less in the thickness direction at 25°C. (Method 2) The conductive paste is applied to a glass plate, and the temperature is raised from 30°C to 175°C over 60 minutes under a nitrogen atmosphere, followed by sintering at 175°C for 120 minutes. This yields a cured product with a thickness of 0.7 mm. The thermal conductivity λ (W / mK) at 25°C of the obtained cured product is measured using the laser flash method. 14. The die shear strength of the Al / heat-treated product of the conductive paste / Cu laminate, measured by the following method 3, is 10 N / mm 2 The conductive paste described in 8. above. (Method 3) The conductive paste is applied to an aluminum plate, and then a copper plate measuring 3.5 mm in length x 3.5 mm in width x 1.5 mm in thickness is placed on the conductive paste, and the temperature is raised from 25°C to 175°C over 150 minutes, and then heat-treated at 175°C for 2 hours to obtain a cured sample. The die shear strength of this cured sample between the aluminum plate and the copper plate is measured at room temperature and a shear rate of 500 μm / sec. 15. The conductive paste described in 8. used as a pressureless bonding paste for bonding the heat dissipation insulating layer and the cooler without pressure. 16. A structure in which the heat dissipation insulating layer and the cooler are bonded by a cured conductive paste described in any one of 8. to 15. 17. 8. to 15. A method for manufacturing a structure, comprising the steps of: applying a conductive paste described in any one of the following to at least one of the cooler and the heat dissipation insulating layer; and joining the heat dissipation insulating layer and the cooler by heat treatment with the cooler and the heat dissipation insulating layer facing each other via the applied conductive paste.

[0087] The present invention will be described in detail below using examples, but the present invention is not limited in any way to the descriptions of these examples.

[0088] (Raw Material Components) First, the components used in the following example are shown. (Component (A): Metal Particles) Ag Particle 1: AG-DSB-114, manufactured by DOWA Electronics Co., Ltd., spherical, average particle size 0.7 μm Ag Particle 2: HKD-13A, manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd., flake-like, average particle size 6.0 μm (Component (B): Thermosetting Resin) Epoxy Resin: Bisphenol-type epoxy resin (product name: RE-303S, manufactured by Nippon Kayaku Co., Ltd.) Acrylic Resin: Ethylene glycol dimethacrylate (product name: Light Ester EG, manufactured by Kyoeisha Chemical Co., Ltd.)

[0089] (Curing agent) Phenol curing agent: Bisphenol F (DIC Corporation, DIC-BPF, melting point 90°C) (Curing accelerator) Curing accelerator 1: 2-phenyl-1H-imidazole-4,5-dimethanol (product name: 2PHZ-PW, Shikoku Chemicals Co., Ltd.) (Radical polymerization initiator) Initiator 1: Dicumyl peroxide (product name: Percadox BC, Kayaku Nourion Co., Ltd.) (Adhesion aid) Adhesion aid 1: Dicyandiamide derivative (product name: EH-3636AS, ADEKA Corporation) (Coupling agent) Coupling agent 1: 3-Methacryloxypropyltrimethoxysilane (product name: KBM-503P, Shin-Etsu Chemical Co., Ltd.) Coupling agent 2: 3-Glycidyloxypropyltrimethoxysilane (product name: KBM-403E, Shin-Etsu Chemical Co., Ltd.) (Solvent) Solvent 1: Ethylene glycol mono-2-ethylhexyl ether (2-ethylhexyl glycol) (Product name: EHG, manufactured by Nippon Emulsifier Co., Ltd.) Solvent 2: Tripropylene glycol mono-n-butyl ether (Product name: BFTG, manufactured by Nippon Emulsifier Co., Ltd.)

[0090] (Examples 1-3, Comparative Example 1) Conductive pastes were prepared by blending the components listed in Table 1, and the physical properties of the heat-treated material and the adhesion were evaluated. The results are shown in Table 1.

[0091] (Method for preparing conductive paste) After pre-mixing each component listed in Table 1, the mixture was kneaded using a three-roller system, and then vacuum degassed to obtain a conductive paste.

[0092] (Thermal conductivity) This was measured by Method 2 described above. Specifically, the conductive paste of each example was applied to a glass plate, and the temperature was raised from 30°C to 175°C over 60 minutes under a nitrogen atmosphere, followed by sintering at 175°C for 120 minutes. This resulted in a hardened product with a thickness of 0.7 mm. The thermal conductivity λ (W / mK) at 25°C was measured for the obtained hardened product using the laser flash method (NETZSCH (NETZSCH Japan Co., Ltd.), LFA467).

[0093] (Storage Modulus) This was measured by Method 1 described above. Specifically, the conductive paste for each example was applied to a glass plate, and the temperature was raised from 30°C to 175°C over 60 minutes under a nitrogen atmosphere, followed by sintering at 175°C for 120 minutes. This resulted in a hardened product with a thickness of 0.05 mm. The storage modulus E' of the obtained hardened product was measured at 250°C and 25°C using a DMA (Hitachi High-Tech Science Corporation, DMS6100) at a frequency of 10 Hz. 250 (GPa) and E' 25 (GPa) was measured for each.

[0094] (Glass transition temperature (Tg), coefficient of linear expansion (CTE1 and CTE2)) Conductive paste obtained in each example was applied to a mold measuring 4 mm in length, 10 mm in width, and 0.15 mm in thickness. The temperature was raised from 30°C to 200°C at a constant rate over 60 minutes, and then heated at 200°C for 120 minutes to prepare a test specimen. Then, using a thermomechanical analyzer (Seiko Instruments, product name: TMA / SS6100), the obtained test specimen was pulled with a load of 10 mN while the temperature was raised from -100°C to 330°C at a heating rate of 5°C / min. The amount of expansion of the test specimen with respect to temperature was detected as an electrical output using a differential transformer, and a graph showing the amount of expansion of the test specimen with respect to temperature was created. Then, Tg was determined from the inflection point of the graph. In addition, the average linear expansion coefficient CTE2 (ppm / °C) at temperatures above the calculated Tg and the average linear expansion coefficient CTE1 (ppm / °C) at temperatures below Tg were measured.

[0095] (Die Shear Strength (DSS)) This was measured by method 3 described above. Specifically, a conductive paste was applied to an aluminum plate, and then a copper plate measuring 3.5 mm in length, 3.5 mm in width, and 1.5 mm in thickness was placed on the conductive paste. The temperature was raised from 25°C to 175°C over 150 minutes, and then heat-treated at 175°C for 2 hours to obtain a cured sample. The die shear strength of this cured sample between the aluminum plate and the copper plate at room temperature and a shear rate of 500 μm / second was measured using a Dage4000 (Nordson Advanced Technologies).

[0096]

[0097] Table 1 shows that the thermal storage modulus E' in Examples 1-3 is 250 The values ​​were within a suitable range, and compared to Comparative Example 1, both the thermal conductivity of the cured conductive paste and the die shear strength of the cured sample joined without pressure were improved. Furthermore, regarding the coefficient of linear expansion, the difference between CTE1 and CTE2 was smaller in Examples 1 to 3 than in Comparative Example 1, and CTE2 was also smaller in Examples 1 to 3 than in Comparative Example 1. As a result, even when a temperature change occurs, such as passing through Tg, rapid thermal expansion or contraction is suppressed, thus effectively suppressing the occurrence of warping.

[0098] This application claims priority based on Japanese Patent Application No. 2025-023990, filed on 18 February 2025, and incorporates all of its disclosures herein.

[0099] 100 Power module 101 Heat dissipation insulating layer 103 Circuit pattern 105 Power semiconductor element 107 Metal plate 109 Cooler 110 Element mounting substrate 111 First junction layer 113 Second junction layer 115 Lead frame 117 Wire 119 Encapsulation material

Claims

1. The device comprises: a heat dissipation insulating layer; a metal circuit pattern provided in direct contact with one surface of the heat dissipation insulating layer; a power semiconductor element mounted on the circuit pattern; a metal plate provided in direct contact with the other surface of the heat dissipation insulating layer; a cooler positioned opposite to the back surface of the metal plate opposite to the heat dissipation insulating layer; and a bonding layer joining the metal plate and the cooler, wherein the bonding layer is formed from a heat-treated conductive paste containing the following components (A) and (B), and the thermal storage modulus E' of the conductive paste is measured at 250°C by the following method 1. 250 However, the power module has a pressure of 0.7 GPa or more and 5 GPa or less. (A) Metal particles (B) Thermosetting resin (Method 1) The conductive paste is applied to a glass plate and heated in a nitrogen atmosphere from 30°C to 175°C over 60 minutes, and then sintered at 175°C for 120 minutes. This yields a cured product with a thickness of 0.05 mm. The storage modulus E' of the obtained cured product at 250°C is measured using a dynamic viscoelasticity analyzer (DMA) at a frequency of 10 Hz. 250 Measure (GPa).

2. The power module according to claim 1, wherein component (A) comprises spherical silver particles and flaky silver particles, and component (A) forms a silver particle linkage structure by heat treatment.

3. The power module according to claim 1 or 2, wherein component (B) comprises one or more selected from the group consisting of epoxy resin, (meth)acrylic resin, silicone resin, and butadiene rubber.

4. The power module according to any one of claims 1 to 3, wherein the material of the cooler on the surface facing the heat dissipation insulating layer is copper or aluminum, and the bonding layer is provided in direct contact with the opposing surface.

5. The storage modulus E' of the conductive paste, measured at 25°C using a method similar to Method 1 above. 25 The power module according to any one of claims 1 to 4, wherein the power output is 5 GPa or more and 20 GPa or less.

6. The power module according to any one of claims 1 to 5, wherein the thermal conductivity of the cured conductive paste, measured by the following method 2, in the thickness direction at 25°C is 10 W / (m·K) or more and 50 W / (m·K) or less. (Method 2) The conductive paste is applied to a glass plate and heated in a nitrogen atmosphere from 30°C to 175°C over 60 minutes, followed by sintering at 175°C for 120 minutes. A cured product with a thickness of 0.7 mm is obtained. The thermal conductivity λ (W / mK) of the obtained cured product at 25°C is measured using the laser flash method.

7. The die shear strength of the Al / conductive paste heat-treated material / Cu laminate, as measured by method 3 below, is 10 N / mm². 2 The power module according to any one of claims 1 to 6. (Method 3) The conductive paste is applied to an aluminum plate, and then a copper plate measuring 3.5 mm in length, 3.5 mm in width, and 1.5 mm in thickness is placed on the conductive paste. The temperature is raised from 25°C to 175°C over 150 minutes, and then heat-treated at 175°C for 2 hours to obtain a cured sample. The die shear strength of the aluminum plate and the copper plate is measured at room temperature and a shear rate of 500 μm / second for this cured sample.

8. A conductive paste interposed between the heat dissipation insulating layer and the cooler of a structure having a power semiconductor element, a heat dissipation insulating layer provided on one side of the power semiconductor element, and a cooler disposed opposite the other side of the heat dissipation insulating layer, for bonding them together, comprising the following components (A) and (B), and the thermal storage modulus E' of the conductive paste measured at 250°C by the following method 1. 250 A conductive paste having a conductivity of 0.7 GPa or more and 5 GPa or less. (A) Metal particles (B) Thermosetting resin (Method 1) The conductive paste is applied to a glass plate and heated in a nitrogen atmosphere from 30°C to 175°C over 60 minutes, followed by sintering at 175°C for 120 minutes. This yields a cured product with a thickness of 0.05 mm. The storage modulus E' of the obtained cured product at 250°C is measured using a dynamic viscoelasticity analyzer (DMA) at a frequency of 10 Hz. 250 Measure (GPa).

9. The conductive paste according to claim 8, wherein component (A) comprises spherical silver particles and flaky silver particles, and component (A) forms a silver particle linkage structure by heat treatment.

10. The conductive paste according to claim 8 or 9, wherein component (B) comprises one or more selected from the group consisting of epoxy resin, (meth)acrylic resin, silicone resin, and butadiene rubber.

11. The conductive paste according to any one of claims 8 to 10, wherein the material of the cooler on the surface facing the heat dissipation insulating layer is copper or aluminum, and the conductive paste is provided in direct contact with the opposing surface.

12. Storage modulus E' of the conductive paste, measured at 25°C using a method similar to Method 1 above. 25 The conductive paste according to any one of claims 8 to 11, wherein the conductivity is 5 GPa or more and 20 GPa or less.

13. A conductive paste according to any one of claims 8 to 12, wherein the thermal conductivity of the cured conductive paste, measured by the following method 2, in the thickness direction at 25°C is 10 W / (m·K) or more and 50 W / (m·K) or less. (Method 2) The conductive paste is applied to a glass plate and heated in a nitrogen atmosphere from 30°C to 175°C over 60 minutes, followed by sintering at 175°C for 120 minutes. A cured product with a thickness of 0.7 mm is obtained. The thermal conductivity λ (W / mK) of the obtained cured product at 25°C is measured using the laser flash method.

14. The die shear strength of the Al / conductive paste heat-treated material / Cu laminate, as measured by the following method 3, is 10 N / mm². 2 The conductive paste described in any one of claims 8 to 13 is described above. (Method 3) The conductive paste is applied to an aluminum plate, and then a copper plate measuring 3.5 mm in length, 3.5 mm in width, and 1.5 mm in thickness is placed on the conductive paste, and the temperature is raised from 25°C to 175°C over 150 minutes, and then heat-treated at 175°C for 2 hours to obtain a cured sample. The die shear strength of the aluminum plate and the copper plate is measured at room temperature and a shear rate of 500 μm / second for this cured sample.

15. The conductive paste according to any one of claims 8 to 14, used as a pressureless bonding paste for joining the heat dissipation insulating layer and the cooler without pressure.

16. A structure in which the heat dissipation insulating layer and the cooler are joined by a cured product of the conductive paste according to any one of claims 8 to 15.

17. A method for manufacturing a structure, comprising the steps of: applying a conductive paste according to any one of claims 8 to 15 to at least one of the cooler and the heat dissipation insulating layer; and joining the heat dissipation insulating layer and the cooler by heat treatment with the cooler and the heat dissipation insulating layer facing each other via the applied conductive paste.

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