Laminated body and method of producing laminated body

Abstract

To provide a laminated body that suppresses the formation of voids at the interface with a substrate, exhibits excellent adhesion and thermal conductivity, and enables large-area fabrication.SOLUTION: The laminated body comprises a first bonding layer, a metal layer, and a second bonding layer in this order. The metal layer has a recess communicating with an outer peripheral edge of the metal layer on a first surface on the side of the first bonding layer and a second surface on the side of the second bonding layer.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a laminate and a method for manufacturing a laminate. [Background technology]

[0002] In large-scale integration (LSI) devices used in various electronic devices, prolonged exposure to high temperatures due to heat generated by the devices can lead to malfunction or breakdown. To prevent this, thermal interface materials (TIMs) are widely used to prevent LSI devices from overheating. Thermal interface materials can prevent overheating by diffusing the heat generated by the devices or by transferring it to a heat-dissipating component that releases it outside the system, such as the atmosphere.

[0003] To date, for example, a method has been proposed for preventing the formation of voids in a solder joint formed between two metal surfaces, in which a slit solder layer having slits formed therein that serve as degassing paths is placed and heated (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-531738 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when using a thermally conductive material containing solder or nanoparticles, residual volatile components contained in the thermally conductive material remain. When heated during bonding to a substrate, the material evaporates and expands, creating voids. This leads to poor adhesion to the substrate and poor thermal conductivity. During bonding, it is necessary to allow volatile components such as solvents and fluxes to escape to the outside of the thermally conductive material. This problem becomes particularly pronounced when bonding a large-area thermally conductive material to a heat-generating element, as the area of ​​the element increases.

[0006] The present invention aims to solve the above-mentioned problems in the prior art and to achieve the following object: That is, the present invention aims to provide a laminate that can suppress the generation of voids at the interface with the substrate, has excellent adhesion and thermal conductivity, and can be made large in area. [Means for solving the problem]

[0007] The means for solving the above problems are as follows: <1> A first bonding layer, a metal layer, and a second bonding layer in this order; The laminate is characterized in that the metal layer has a recess on a first surface on the side of the first bonding layer and a second surface on the side of the second bonding layer, the recess communicating with the outer periphery of the metal layer. <2> The depth of the recess is 1 μm or more. <1> 1. The laminate according to claim 1. <3> The shape pattern of the recesses is at least one of a radial shape, a lattice shape, a linear shape, and an embossed shape. <1> or <2> 1. The laminate according to claim 1. <4> The metal layer contains one or more selected from the group consisting of Cu, Al, Ag, Au, Fe, and Pt. <1> from <3> The laminate according to any one of the above items. <5> The first bonding layer and the second bonding layer have notches at locations corresponding to the recesses of the metal layer. <1> from <4> The laminate according to any one of the above items. <6> the first surface of the metal layer has a concave shape with a radius of curvature R represented by the following formula (1), The radius of curvature R is 500 mm or more and 5000 mm or less. <1> from <5> The laminate according to any one of the above items. Formula (1): R=(x 2 +y 2 ) / 2 / y In the formula (1), x represents the distance between the center c and the end e on the first surface of the metal layer, and y represents the difference (Te-Tc) between the thickness Te of the end e and the thickness Tc of the center c of the metal layer. <7> The first bonding layer and / or the second bonding layer is a low-melting-point metal layer containing a low-melting-point metal. <1> from <6> The laminate according to any one of the above items. <8> The low melting point metal is at least one selected from the group consisting of In, Ga, Sn, Zn, and Bi. <7> 1. The laminate according to claim 1. <9> The low melting point metal is at least one selected from the group consisting of Sn-Pb solder, Pb-Sn-Sb solder, Sn-Sb solder, Sn-Pb-Bi solder, Sn-Bi solder, Sn-Bi-Ag solder, Sn-Cu solder, Sn-Pb-Cu solder, Sn-In solder, Sn-Ag solder, Sn-Pb-Ag solder, Pb-Ag solder, and Sn-Ag-Cu solder. <7> 1. The laminate according to claim 1. <10> The above-mentioned film further has a polyfunctional carboxylic acid layer containing a trifunctional or higher polyfunctional carboxylic acid on the low-melting point metal layer. <7> from <9> The laminate according to any one of the above items. <11> The first bonding layer and / or the second bonding layer is a thermally conductive particle-containing layer containing thermally conductive particles. <1> from <10> The laminate according to any one of the above items. <12> a recess forming step of forming recesses on the first surface and the second surface of the metal layer, the recesses communicating with the outer periphery of the metal layer; a bonding layer forming step of forming a first bonding layer and a second bonding layer on the first surface and the second surface of the metal layer having the recess; The method for producing a laminate is characterized by comprising the steps of: <13> The bonding layer forming step is a step of forming a bonding layer by transferring a bonding layer provided on a transfer substrate. <12> 1. A method for producing the laminate described in . <14> the first surface of the metal layer has a concave shape with a radius of curvature R expressed by the following formula (1), The radius of curvature R is 500 mm or more and 5000 mm or less. <12> or <13> 1. A method for producing the laminate described in . Formula (1): R=(x 2 +y 2 ) / 2 / y In the formula (1), x represents the distance between the center c and the end e on the first surface of the metal layer, and y represents the difference (Te-Tc) between the thickness Te of the end e and the thickness Tc of the center c of the metal layer. <15> The bonding layer forming step is a step of transferring a bonding layer provided on a transfer substrate using a pressing tool having a convex curvature radius corresponding to the curvature radius R to form a bonding layer. <14> 1. A method for producing the laminate described in . <16> The first bonding layer and the second bonding layer have notches at locations corresponding to the recesses of the metal layer. <12> from <15> 1. A method for producing the laminate according to any one of the above. <17> the bonding layer forming step is a step of providing a spacer having a shape of the recess of the metal layer and a total thickness of the recess and the bonding layer in the recess of the metal layer, and applying a thermally conductive composition containing thermally conductive particles to form a thermally conductive particle-containing layer; <16> 1. A method for producing the laminate described in . [Effects of the Invention]

[0008] According to the present invention, the above-mentioned problems in the prior art can be solved, the above-mentioned objects can be achieved, and a laminate can be provided which can suppress the generation of voids at the interface with the substrate, has excellent adhesion and thermal conductivity, and can be made large in area. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing an example of the laminate of this embodiment. [Figure 2] FIG. 2 is a schematic view showing another example of the laminate of the present embodiment. [Figure 3] FIG. 3 is a schematic view showing another example of the laminate of the present embodiment. [Figure 4] FIG. 4 is a schematic view showing another example of the laminate of the present embodiment. [Figure 5] FIG. 5 is an explanatory diagram of the radius of curvature R of the metal layer 12 in FIG. [Figure 6] FIG. 6 is a schematic diagram showing an example of a radial pattern of recesses in a metal layer. [Figure 7] FIG. 7 is a schematic diagram showing an example of a grid pattern of recesses in a metal layer. [Figure 8] FIG. 8 is a schematic diagram showing an example of a linear pattern of recesses in a metal layer. [Figure 9] FIG. 9 is an explanatory diagram (part 1) of the process of the method for producing the laminate of this embodiment. [Figure 10] FIG. 10 is an explanatory diagram (part 1) of the process of the method for producing the laminate of this embodiment. [Figure 11] FIG. 11 is an explanatory diagram (part 2) of the process of the method for producing the laminate of this embodiment. [Figure 12] FIG. 12 is an explanatory diagram (part 3) of the process of the method for producing a laminate according to this embodiment. [Figure 13] FIG. 13 is an explanatory diagram (part 4) of the process of the method for producing a laminate according to this embodiment. [Figure 14] FIG. 14 is an explanatory diagram (part 5) of the process of the method for producing a laminate according to this embodiment. [Figure 15] FIG. 15 is an explanatory diagram (part 6) of the process of the method for producing a laminate according to this embodiment. [Figure 16] FIG. 16 is an explanatory diagram (part 7) of the process of the method for producing a laminate according to this embodiment. [Figure 17] FIG. 17 is an explanatory diagram (part 8) of the process of the method for producing a laminate according to this embodiment. [Figure 18] FIG. 18 is an explanatory diagram (part 9) of the process of the method for producing a laminate according to this embodiment. [Figure 19] FIG. 19 is an explanatory diagram (part 10) of the process of the method for producing a laminate according to this embodiment. [Figure 20] FIG. 20 is a schematic cross-sectional view showing an example of the heat dissipation structure of this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Laminate) The laminate of this embodiment has a first bonding layer, a metal layer, and a second bonding layer in this order, and may further have other members as necessary. The metal layer has recesses on a first surface on the side of the first bonding layer and a second surface on the side of the second bonding layer, the recesses communicating with the outer periphery of the metal layer. The laminate may further include a first substrate and a second substrate, in which case it includes the first substrate, a first bonding layer, a metal layer, a second bonding layer, and the second substrate in this order.

[0011] The present invention is based on the inventors' discovery of problems in the prior art. Specifically, the prior art method described in Patent Document 1, in which a slit solder layer with slits that serve as degassing channels is provided and heated, can remove a certain amount of volatile components through the slits that serve as degassing channels. However, when the slits are formed in the solder layer and heated during bonding, the slits are blocked by the reflow of the solder layer at the beginning of heating, which still creates the risk of voids forming. This problem becomes particularly pronounced when large-area elements are bonded using large-area slit solder layers as the elements become larger.

[0012] As a result of intensive research, the inventors have found that in the laminate of this embodiment, the metal layer has recesses on the first surface on the side of the first bonding layer and the second surface on the side of the second bonding layer that are connected to the outer periphery of the metal layer, so that the volatile components that volatilize and expand when heated can flow through the recesses that are connected to the outer periphery and be released to the outside of the system, thereby further suppressing the generation of voids at the interface with the substrate and realizing a laminate that has excellent adhesion and thermal conductivity and can be made large in area. In this case, it is preferable that the metal layer has recesses communicating with the outer periphery on the entire surface of the first surface and the entire surface of the second surface from the viewpoint of efficiency in releasing volatile components to the outside of the system.

[0013] <Metal layer> The metal layer is a layer containing metal, and has recesses on a first surface on the side of the first bonding layer and a second surface on the side of the second bonding layer, the recesses communicating with the outer periphery of the metal layer. The metal is not particularly limited and can be appropriately selected depending on the purpose, but a metal with high thermal conductivity and relatively soft properties is preferred, and it is preferable that the metal contains one or more selected from the group consisting of Cu, Al, Ag, Au, Fe, and Pt. The metals may be one type alone or may be an alloy of two or more types in combination. Among these, metal plates made of the above metals are preferred, and copper plates are more preferred from the viewpoints of thermal conductivity, stability, and economy.

[0014] The metal layer is not particularly limited in shape, structure, size, material, etc., as long as it is a layer containing a metal, and can be appropriately selected depending on the purpose. The metal layer may be in the form of, for example, a plate, a sheet, or a foil. The metal layer may have a single layer structure or a laminated structure. The size of the metal layer can be appropriately selected depending on the application, etc., but it is possible to make it large, for example, 100 mm 2 It can be used for larger areas, such as 400mm 2 More than 900mm is preferable. 2 The above is more preferable.

[0015] The average thickness of the metal layer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 50 μm to 1000 μm, more preferably 100 μm to 800 μm, and even more preferably 200 μm to 600 μm.

[0016] -Recess- The shape of the recess is not particularly limited and can be appropriately selected depending on the purpose. It may be an irregular shape, but is preferably, for example, a triangular prism, triangular pyramid, square prism, square pyramid, pentagonal prism, pentagonal pyramid, hexagonal prism, hexagonal pyramid, heptagonal prism, heptagonal pyramid, octagonal prism, octagonal pyramid, cylinder, cone, semicircle, or the like.

[0017] The depth of the recesses is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 1 μm or more, and more preferably 1 μm or more and 15 μm or less. The maximum width of the recess is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 5 μm or more, and more preferably 10 μm or more and 100 μm or less. The pitch, which is the shortest distance between the centers of adjacent recesses, is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 10 μm or more, and more preferably 10 μm or more and 100 μm or less.

[0018] The shape pattern of the recesses when viewed from above is preferably at least one of a radial pattern, a lattice pattern, a linear pattern, and an embossed pattern. From the viewpoint of maintaining the strength of the metal layer while thinning it, it is preferable that the shape pattern of the recesses on the first surface of the metal layer and the shape pattern of the recesses on the second surface of the metal layer do not completely overlap in the direction perpendicular to the metal layer, but they may partially overlap, and may have through holes that penetrate through the first surface and the second surface of the metal layer.

[0019] [Aspect in which the first surface of the metal layer has a curved surface] The metal layer may have a first surface that has a curved surface. Specifically, in one embodiment, it is preferable that the first surface of the metal layer has a concave shape with a radius of curvature R expressed by the following formula (1): Formula (1): R=(x 2 +y 2 ) / 2 / y In the formula (1), x represents the distance between the center c and the edge e on the first surface of the metal layer, and y represents the difference (Te-Tc) between the thickness Te of the edge e and the thickness Tc of the center c of the metal layer, in mm.

[0020] The first surface of the metal plate is the surface on the heating element side, and is preferably in contact with a first base material that is a part of the heating element via a first bonding layer. When the heat generating element is mounted on the support substrate, it may deform into a convex shape, and when the heat generating element is joined to the heat dissipation member via a thermally conductive member, the adhesion to the thermally conductive member may be reduced, resulting in a problem of worsening thermal resistance around the heat generating element. In contrast, in an embodiment in which the first surface of the metal layer has a curved surface, the laminate has a curved surface that follows the deformation of the heat generating element, thereby achieving even better adhesion and thermal conductivity.

[0021] Specifically, consider a case where the base material of an IC (heat generating element) is made of silicon, and the support substrate on which the IC is mounted is a printed circuit board (PCB), a composite material of wiring metals such as copper and resin. The linear expansion coefficient of silicon is approximately 2.6 ppm / K, while the linear expansion coefficient of a PCB is approximately 9 ppm / K to 16 ppm / K. When mounting the PCB and IC using standard solder, the mounting is performed at a high temperature of 200 to 300°C. In other words, when the PCB and IC are bonded together without distortion at high temperatures and then cooled to room temperature, significant deformation occurs due to the difference in the linear expansion coefficients of the PCB and IC, resulting in convex distortion of the first base material of the IC (heat generating element). In fact, convex distortion of the first base material is a problem in the semiconductor manufacturing process.

[0022] Assuming that the contact surface of the first substrate with the metal layer has a spherical convex shape, the convex shape can be expressed as a convex shape with a radius of curvature R' expressed by the following formula (2). Formula (2): R'=(x 2 +y 2 ) / 2 / y In the formula (2), x represents the distance between the center c and the end e of the contact surface of the first substrate, and y represents the difference (Te-Tc) between the thickness Te of the end e and the thickness Tc of the center c of the first substrate, expressed in mm.

[0023] The present inventors have confirmed that the radius of curvature R' of the first base material can be appropriately changed depending on various conditions, such as the heating temperature during mounting of the heating element on the support substrate and the ratio (size ratio) of the length of one side of the support substrate (e.g., a printed circuit board (PCB)) to the first base material during mounting. When the heating temperature during mounting is high (e.g., 200°C or higher) or when the size ratio of the support substrate (PCB) to the first base material during mounting is large (e.g., 2 or higher), the radius of curvature R' tends to become smaller (i.e., deformation becomes larger), and can be, for example, 4000 mm or less, 3000 mm or less, or 2000 mm or less.

[0024] The radius of curvature R can be appropriately selected depending on the convex shape of the radius of curvature R' of the first substrate, but is preferably 500 mm or more and 5000 mm or less, more preferably 1000 mm or more and 5000 mm or less. Furthermore, it is preferable that the radius of curvature R is equal to or larger than the radius of curvature R'.

[0025] When the first surface of the metal layer has a curved surface, the maximum thickness y of the metal layer, i.e., the difference (Te-Tc) between the thickness Te of the end e of the first substrate and the thickness Tc of the center c, is preferably 50 μm or more and 1000 μm or less, more preferably 100 μm or more and 800 μm or less, and even more preferably 200 μm or more and 600 μm or less. Furthermore, the minimum thickness of the metal layer (for example, the thickness Tc at the center c) may be 0 μm (i.e., the metal layer has through holes that penetrate the first surface and the second surface) as long as the shape of the metal layer can be maintained, and from the viewpoint of thinning the laminate, it is preferably 0 μm or more and 300 μm or less, more preferably 0 μm or more and 100 μm or less, and even more preferably 0 μm or more and 100 μm or less.

[0026] When the first surface of the metal layer has a curved surface, the shape pattern of the recesses when viewed from above on the first surface is preferably radial, and more preferably radial around the center c of the metal layer, or a combination of circular and radial shapes around the center c of the metal layer.

[0027] <First substrate> The first base material may be the heat generating element (electronic component) itself in the heat dissipation structure, or may be a member such as a lid (sealing cover) of the heat generating element. The shape, structure, size, material, etc. of the first substrate are not particularly limited and can be appropriately selected depending on the purpose. Examples of the shape of the first substrate include a plate shape, a sheet shape, etc. Examples of the structure of the first substrate include a single-layer structure, a laminated structure, etc. The size of the first substrate can be appropriately selected depending on the application, etc.

[0028] The material of the first base material is a material that is difficult to wet with solder, and examples thereof include silicon (Si), aluminum, tungsten, molybdenum, glass, molded resin, stainless steel, ceramics, etc. These may be used alone or in combination of two or more. Examples of the ceramics include aluminum nitride, silicon carbide, alumina, and gallium nitride. Examples of the molding resin include epoxy resin, silicone resin, urethane resin, and acrylic resin. Among these, silicon (Si) is suitable as the material for the first base material. The average thickness of the first substrate is not particularly limited and can be appropriately selected depending on the purpose.

[0029] <Second substrate> The second base material may be the heat spreader itself in the heat dissipation structure, or may be a part of the heat spreader. The second substrate is disposed opposite the first substrate, and its shape, structure, size, material, etc. are not particularly limited and can be appropriately selected depending on the purpose. Examples of the shape of the second substrate include a plate shape, a sheet shape, etc. Examples of the structure of the second substrate include a single-layer structure, a laminated structure, etc. The size of the second substrate can be appropriately selected depending on the application, etc.

[0030] The material of the second substrate is a material that is easily wetted by solder, and examples thereof include copper, gold, platinum, palladium, silver, zinc, iron, tin, nickel, magnesium, indium, and alloys thereof. These may be used alone or in combination of two or more. Among these, copper is suitable as the material of the second substrate. The average thickness of the second substrate is not particularly limited and can be appropriately selected depending on the purpose. Hereinafter, the first substrate and the second substrate may be collectively referred to as "substrate".

[0031] <First bonding layer, second bonding layer> The first bonding layer and the second bonding layer are collectively referred to as "bonding layers." The bonding layer is not particularly limited as long as it has thermal conductivity and can bond the metal layer and the substrate, and can be appropriately selected depending on the purpose. Examples include a low-melting point metal layer and a layer containing thermally conductive particles. Among these, a low-melting-point metal layer is preferred because it can suitably suppress the generation of voids without blocking recesses in the metal layer during bonding and release of volatile components to the outside of the system. The first bonding layer and the second bonding layer may be formed of the same material, or may be formed of different materials.

[0032] The shape of the bonding layer may be, for example, a plate or a sheet. The structure of the bonding layer may be a single-layer structure or a laminated structure. The size of the bonding layer may be appropriately selected depending on the application, etc.

[0033] [Aspect in which the bonding layer has a notch] The bonding layer preferably has a notch at a position corresponding to the recess in the metal layer, and more preferably the surface of the bonding layer that comes into contact with the metal layer has the same pattern as the top surface of the metal layer. In this case, the bonding layer may be either a low-melting-point metal layer or a thermally conductive particle-containing layer, which is preferable in that it does not block the recesses in the metal layer during bonding and can more effectively suppress the occurrence of voids. The cutout portion may be, for example, a recess or a cutout portion, but is preferably a cutout portion in terms of thinning the laminate and the bonding layer.

[0034] The method for forming the bonding layer having the cutout portion is not particularly limited and can be appropriately selected depending on the purpose. Examples include a method of embossing or die-cutting a sheet-like bonding layer provided on a transfer substrate; a method of transferring a sheet-like bonding layer provided on a transfer substrate onto a metal layer having a recess, and transferring the bonding layer having the cutout portion to the contact surface with the metal layer; and a method of providing a spacer having the shape of the recess of the metal layer and the total thickness of the recess and the bonding layer in the recess of the metal layer, and applying a thermally conductive composition containing thermally conductive particles to form a thermally conductive particle-containing layer.

[0035] <<Low melting point metal layer>> The low-melting-point metal layer is a layer containing a low-melting-point metal. The low-melting point metal is not particularly limited and can be appropriately selected depending on the purpose, but is preferably one or more selected from the group consisting of In, Ga, Sn, Zn, and Bi; and / or a solder material. Among these, In is preferred from the viewpoints of lower hardness than other metal elements, high conformability to the surfaces of the first and second substrates, and high adhesion.

[0036] The solder material is preferably at least one selected from the group consisting of Sn-Pb solder, Pb-Sn-Sb solder, Sn-Sb solder, Sn-Pb-Bi solder, Sn-Bi solder, Sn-Bi-Ag solder, Sn-Cu solder, Sn-Pb-Cu solder, Sn-In solder, Sn-Ag solder, Sn-Pb-Ag solder, Pb-Ag solder, and Sn-Ag-Cu solder.

[0037] The low-melting-point metal layer may be formed into a sheet shape from the low-melting-point metal, or may be a commercially available product, such as an indium sheet (product name: 4N In sheet, manufactured by Nippon Invest Co., Ltd., average thickness 100 μm), an indium sheet (product name: Indium sheet, manufactured by Axis Co., Ltd., average thickness 100 μm), or a sheet-shaped solder (product name: M705 alloy, manufactured by Senju Metal Industry Co., Ltd., alloy composition (wt%): Sn-3.0Ag-0.5Cu, average thickness 50 μm).

[0038] The melting point of the low-melting-point metal is preferably 100°C or higher and 250°C or lower, and more preferably 120°C or higher and 200°C or lower. The melting point of the low-melting-point metal is preferably lower than the heating temperature in the bonding step in the manufacturing method of the laminate of this embodiment, which will be described later.

[0039] The average thickness of the low melting point metal layer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 20 μm or more and 500 μm or less, and more preferably 50 μm or more and 200 μm or less.

[0040] -Multifunctional carboxylic acid layer- It is preferable to further have a polyfunctional carboxylic acid layer containing a trifunctional or higher polyfunctional carboxylic acid on the low-melting point metal layer, since this can reduce contact resistance with the substrate and achieve excellent thermal conductivity and adhesion. Here, "on the low-melting-point metal layer" means the surface of the low-melting-point metal layer that comes into contact with at least one of the metal layer, the first substrate, and the second substrate. Among these, it is preferable to provide the polyfunctional carboxylic acid layer on the surface that comes into contact with the metal layer having recesses, since this allows volatile components including the polyfunctional carboxylic acid to be effectively discharged to the outside of the laminate during the bonding step in manufacturing the laminate. A laminate having a multifunctional carboxylic acid layer on a low-melting-point metal layer can achieve a thermal conductivity of 20 W / (m·K) or more.

[0041] It is known that if the contact surface between the low-melting-point metal layer and at least one of the metal layer, first substrate, and second substrate is oxidized, surface roughness and thermal resistance occur, and thermal conductivity decreases, and carboxylic acid can remove low-melting-point metal oxides according to the following reaction formula: By having a polyfunctional carboxylic acid layer on the low-melting-point metal layer, excellent thermal conductivity and adhesion can be achieved, and it is inferred that low-melting-point metal oxides are removed. Oxide of low-melting metal + carboxylic acid → low-melting metal + reaction product with carboxylic acid + water

[0042] The content of the polyfunctional carboxylic acid per area of ​​the polyfunctional carboxylic acid layer is 0.002 μg / mm 2 More than 0.5μg / mm 2 Preferably less than 0.005 μg / mm 2 More than 0.2μg / mm 2 Less than 0.01 μg / mm is more preferable. 2 More than 0.1μg / mm 2 The following is even more preferred:

[0043] -Polyfunctional carboxylic acid- The polyfunctional carboxylic acid is not particularly limited and can be appropriately selected depending on the purpose as long as it is a trifunctional or higher polyfunctional carboxylic acid, but a polyfunctional carboxylic acid represented by the following general formula (I) is more preferred. These may be used alone or in combination of two or more.

[0044] [ka] In the general formula (I), R1 to R3 each independently represent an alkylene group, a lactone skeleton, or a bond, R4 represents a hydrogen atom or an alkyl group optionally substituted with a hydroxyl group, and R5 represents an alkylene group having 1 to 3 carbon atoms or an alkenyl group having 2 to 3 carbon atoms.

[0045] The alkylene group for R1 to R3 in the general formula (I) is preferably an alkylene group having 1 to 10 carbon atoms, and examples thereof include a methylene group, an ethylene group, a propylene group, an isopropylene group, a butylene group, a hexylene group, a heptylene group, an octylene group, a 2-ethylhexylene group, a tert-octylene group, and a cyclohexylene group. Examples of the lactone skeleton in R1 to R3 in the general formula (I) include skeletons such as α-acetolactone, β-propiolactone, γ-butyrolactone, δ-valerolactone, and ε-caprolactone.

[0046] When at least one of R1 to R3 is a caprolactone skeleton, each of -R10-, -R20-, and -R30- is represented by the following general formula (i).

[0047] [ka] In the general formula (i), n represents an integer of 1 or more, preferably 1 to 10.

[0048] Examples of the alkyl group which may be substituted with a hydroxyl group in R4 include a methyl group, an ethyl group, a propyl group, -(CH2)-OH, -(CH2)2-OH, and -(CH2)3-OH.

[0049] Examples of the alkylene group having 1 to 3 carbon atoms in R5 include a methylene group, an ethylene group, a propylene group, and an isopropylene group. Examples of the alkenyl group having 2 to 3 carbon atoms for R5 include a vinyl group, a 1-propenyl group, and an allyl group (2-propenyl group). R5 is preferably either an alkyl group having 2 to 3 carbon atoms or an alkenyl group having 2 carbon atoms, as this provides excellent flux activity and curability.

[0050] The polyfunctional carboxylic acid represented by the general formula (I) can be synthesized by reacting a specific acid anhydride with a specific polyfunctional alcohol, as will be explained below.

[0051] [Method of producing polyfunctional carboxylic acid] The method for producing the polyfunctional carboxylic acid includes a step of esterifying an acid anhydride with a polyfunctional alcohol, and may further include other steps as necessary. The esterification reaction between the acid anhydride and the polyfunctional alcohol is not particularly limited and may be appropriately selected depending on the purpose.

[0052] Examples of the acid anhydride include succinic anhydride, glutaric anhydride, maleic anhydride, phthalic anhydride, benzoic anhydride, oxalic anhydride, etc. These may be used alone or in combination of two or more. Of these, succinic anhydride, glutaric anhydride, and maleic anhydride are preferred.

[0053] The polyfunctional alcohol is trifunctional or more, preferably trifunctional or tetrafunctional. Examples of the polyfunctional alcohol include lactone derivatives such as caprolactone derivatives, glycerin, trimethylolpropane, and pentaerythritol. These may be used alone or in combination of two or more. Of these, glycerin and caprolactone derivatives are preferred.

[0054] Examples of the caprolactone derivative include compounds having a caprolactone skeleton represented by the general formula (i). Commercially available caprolactone derivatives can be used, and examples of the commercially available products include PLACCEL 205, PLACCEL 205U, PLACCEL 303, and PLACCEL 410 (all manufactured by Daicel Corporation).

[0055] An example of the esterification reaction between a specific acid anhydride and a trifunctional alcohol is shown below. [ka] In the reaction formula, R1 to R3 represent an alkylene group, a lactone skeleton, or a bond. R4 represents a hydrogen atom or an alkyl group which may be substituted with a hydroxyl group. R5 represents an alkylene group having 1 to 3 carbon atoms or an alkenyl group having 2 to 3 carbon atoms.

[0056] The other steps are not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include a concentration step and a separation and purification step.

[0057] The polyfunctional carboxylic acid represented by the general formula (I) exhibits a good fluxing effect. That is, the polyfunctional carboxylic acid represented by the general formula (I) remains liquid from room temperature to high temperature, does not undergo any reaction during film formation, and can improve the wettability of the coating liquid. When heated in stages, the first heating stage exerts a fluxing effect, and then the second heating stage and cooling to room temperature melt and solidify the low-melting-point metal, resulting in lamination with the silicon substrate or opposing substrate to which the flux is to be applied. The first stage of heating is preferably performed at a temperature of 120°C to 150°C, for example. The second stage of heating is preferably performed at a temperature equal to or higher than the melting point of the low-melting-point metal, for example, 150°C to 190°C.

[0058] The polyfunctional carboxylic acid is preferably liquid at 25°C and 150°C. Here, being liquid means having fluidity that allows application. Whether the polyfunctional carboxylic acid is liquid at 25°C and 150°C can be confirmed, for example, by visually confirming fluidity at 25°C (room temperature) and by the presence or absence of an absorption peak up to 150°C by DSC. The molecular weight of the polyfunctional carboxylic acid is preferably 800 g / mol or less, more preferably 400 g / mol or more and 700 g / mol or less, because it is a liquid. The molecular weight of the polyfunctional carboxylic acid can be measured, for example, using Shodex (registered trademark) GPC-101 (a product of Showa Denko K.K.).

[0059] <<Thermal Conduction Particle-Containing Layer>> The thermally conductive particle-containing layer contains thermally conductive particles, and further contains other components as required. The thermally conductive particle-containing layer is preferably formed by curing a thermally conductive composition containing thermally conductive particles. The thermally conductive composition contains thermally conductive particles, a curing component, and a curing agent for curing the curing component, and preferably contains low-melting-point metal particles and a polymer, and further contains other components as necessary.

[0060] -Thermal Conduction Particles- The thermally conductive particles are preferably at least one of copper particles, silver-coated particles, and silver particles. Examples of the silver-coated particles include silver-coated copper particles, silver-coated nickel particles, and silver-coated aluminum particles. The shape of the thermally conductive particles is not particularly limited and can be appropriately selected depending on the purpose. Examples include spherical, flat, granular, and needle-like shapes. The thermally conductive particles preferably have a volume average particle size of 1 μm to 100 μm, more preferably 10 μm to 70 μm, and even more preferably 10 μm to 50 μm. When the thermally conductive particles have a volume average particle size of 1 μm to 100 μm, the volume ratio of the thermally conductive particles to the low-melting-point metal particles can be increased, thereby achieving high thermal conductivity. The volume average particle size can be measured, for example, by a laser diffraction / scattering particle size distribution measuring device (Microtrac MT3300EXII, manufactured by Microtrac Bell Co., Ltd.).

[0061] -Low melting point metal particles- As the low melting point metal particles, solder particles as specified in JIS Z3282-1999 are preferably used. Examples of the solder particles include Sn-Pb solder particles, Pb-Sn-Sb solder particles, Sn-Sb solder particles, Sn-Pb-Bi solder particles, Sn-Bi-Ag solder particles, Sn-Cu solder particles, Sn-Pb-Cu solder particles, Sn-In solder particles, Sn-Ag solder particles, Sn-Pb-Ag solder particles, Pb-Ag solder particles, Sn-Ag-Cu solder particles, etc. These may be used alone or in combination of two or more. Among these, solder particles containing Sn and at least one selected from Bi, Ag, Cu, and In are preferred, and Sn-Bi based solder particles, Sn-Bi-Ag based solder particles, Sn-Ag-Cu based solder particles, and Sn-In based solder particles are more preferred.

[0062] The shape of the low melting point metal particles is not particularly limited and can be appropriately selected depending on the purpose. Examples include spherical, flat, granular, and needle-like shapes. The melting point of the low-melting-point metal particles is preferably 100°C or higher and 250°C or lower, and more preferably 120°C or higher and 200°C or lower. It is preferable that the melting point of the low-melting-point metal particles is lower than the thermal curing temperature of the thermal conductive composition, since the low-melting-point metal particles melted in the cured product of the thermal conductive composition can form a network (a continuous metal phase) via the thermal conductive particles, thereby achieving high thermal conductivity. The low-melting-point metal particles react with the thermally conductive particles under the conditions of the thermal curing treatment of the thermally conductive composition to form an alloy with a higher melting point than the low-melting-point metal particles, thereby preventing melting at high temperatures and improving reliability and heat resistance of the cured product of the thermally conductive composition. The thermal curing treatment of the thermal conductive composition is carried out, for example, at a temperature of 150° C. to 200° C. for 30 minutes to 2 hours.

[0063] The volume average particle size of the low-melting-point metal particles is preferably 10 μm or less, more preferably 1 μm or more and 5 μm or less. When the volume average particle size of the low-melting-point metal particles is 10 μm or less, the volume ratio of the low-melting-point metal particles to the thermally conductive particles can be reduced, thereby achieving high thermal conductivity. The volume average particle size of the low-melting-point metal particles can be measured in the same manner as the volume average particle size of the thermally conductive particles.

[0064] The volume average particle size of the thermally conductive particles is larger than the volume average particle size of the low-melting-point metal particles, and the volume average particle size ratio (A / B) of the thermally conductive particles A to the low-melting-point metal particles B is preferably 2 or more, more preferably 3 or more, and even more preferably 5 or more. The upper limit of the volume average particle size ratio (A / B) is preferably 20 or less, more preferably 10 or less. By using low-melting-point metal particles with a smaller volume average particle size than the thermally conductive particles, the thermally conductive particles become the main component in the thermally conductive composition, and the low-melting-point metal particles present between the thermally conductive particles melt when heated and alloy with the thermally conductive particles to form a network, thereby achieving high thermal conductivity.

[0065] -Curing component- As the curing component, it is preferable to use at least one of an oxirane ring compound and an oxetane compound.

[0066] --Oxirane ring compounds-- The oxirane ring compound is a compound having an oxirane ring, and examples thereof include epoxy resins. The epoxy resin is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include glycidyl ether type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, bisphenol A type epoxy resins, trisphenol type epoxy resins, tetraphenol type epoxy resins, phenol-xylylene type epoxy resins, naphthol-xylylene type epoxy resins, phenol-naphthol type epoxy resins, phenol-dicyclopentadiene type epoxy resins, alicyclic epoxy resins, aliphatic epoxy resins, etc. These may be used alone or in combination of two or more.

[0067] --Oxetane compounds-- The oxetane compound is a compound having an oxetanyl group, and may be an aliphatic compound, an alicyclic compound, or an aromatic compound. The oxetane compound may be a monofunctional oxetane compound having only one oxetanyl group, or may be a polyfunctional oxetane compound having two or more oxetanyl groups.

[0068] The oxetane compound is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include 3,7-bis(3-oxetanyl)-5-oxa-nonane, 1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene, 1,2-bis[(3-ethyl-3-oxetanylmethoxy)methyl]ethane, 1,3-bis[(3-ethyl-3-oxetanylmethoxy)methyl]propane, ethylene glycol bis(3-ethyl-3-oxetanylmethyl)ether, triethylene glycol bis(3-ethyl-3-oxetanylmethyl)ether, tetraethylene glycol bis(3-ethyl-3-oxetanylmethyl)ether, 1,4 -bis(3-ethyl-3-oxetanylmethoxy)butane, 1,6-bis(3-ethyl-3-oxetanylmethoxy)hexane, 3-ethyl-3-(phenoxy)methyloxetane, 3-ethyl-3-(cyclohexyloxymethyl)oxetane, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3-(chloromethyl)oxetane, 3-ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane, xylylenebisoxetane, 4,4'-bis[(3-ethyl-3-oxetanyl)methoxymethyl]biphenyl (OXBP), etc. These may be used alone or in combination of two or more.

[0069] As the oxetane compound, commercially available products can be used, and examples of the commercially available products include the "Aron Oxetane (registered trademark)" series sold by Toagosei Co., Ltd. and the "ETERNACOLL (registered trademark)" series sold by Ube Industries, Ltd.

[0070] Among the oxirane ring compounds and oxetane compounds, glycidyl ether type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, phenol-dicyclopentadiene type epoxy resins, bisphenol A type epoxy resins, aliphatic epoxy resins, and 4,4'-bis[(3-ethyl-3-oxetanyl)methoxymethyl]biphenyl (OXBP) are preferred.

[0071] The content of the curing component is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 0.5% by mass or more and 60% by mass or less based on the total amount of the thermosetting composition.

[0072] - Hardener - The curing agent is a curing agent corresponding to the curing component, and examples thereof include polyaddition-type curing agents such as acid anhydride-based curing agents, aliphatic amine-based curing agents, aromatic amine-based curing agents, phenol-based curing agents, and mercaptan-based curing agents, and catalyst-type curing agents such as imidazole. These may be used alone or in combination of two or more. Among these, acid anhydride-based curing agents are preferred. When the curing component is an epoxy resin, the acid anhydride-based curing agent is preferred because it does not generate gas during thermal curing, can achieve a long pot life when mixed with the epoxy resin, and can achieve a good balance between the electrical properties, chemical properties, and mechanical properties of the resulting cured product. Examples of the acid anhydride curing agent include cyclohexane-1,2-dicarboxylic acid anhydride and mono-acid anhydrides of tricarboxylic acids. Examples of the mono-acid anhydrides of tricarboxylic acids include cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride.

[0073] The curing agent preferably has flux activity, as this improves the wettability of the molten low-melting-point metal particles to the thermally conductive particles. Examples of methods for imparting flux activity to the curing agent include introducing protonic acid groups, such as carboxyl groups, sulfonyl groups, and phosphate groups, into the curing agent by known methods. Among these, the introduction of carboxyl groups is preferred in terms of reactivity with the epoxy resin or oxetane compound used as the curing component. Examples of such groups include carboxyl-containing organic acids, such as glutaric acid and succinic acid. Alternatively, compounds modified from glutaric anhydride or succinic anhydride, or metal salts of organic acids, such as silver glutarate, may also be used.

[0074] The content of the curing agent is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 0.1% by mass or more and 30% by mass or less based on the total amount of the thermosetting composition.

[0075] -polymer- The thermosetting composition preferably contains a polymer to impart flexibility and the like. The polymer is not particularly limited and can be appropriately selected depending on the purpose. Examples include polymers having at least one structure selected from a polybutadiene structure, a polysiloxane structure, a poly(meth)acrylate structure, a polyalkylene structure, a polyalkyleneoxy structure, a polyisoprene structure, a polyisobutylene structure, a polyamide structure, and a polycarbonate structure in the molecule. The content of the polymer is preferably from 1 to 50% by mass, more preferably from 1 to 30% by mass, and even more preferably from 1 to 10% by mass, based on the total amount of the thermosetting composition.

[0076] -Other ingredients- The thermosetting composition may contain other components as long as the effects of the present invention are not impaired. The other components are not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include non-metallic thermally conductive particles (e.g., aluminum nitride, alumina, carbon fiber, etc.), additives (e.g., antioxidants, ultraviolet absorbers, curing accelerators, silane coupling agents, leveling agents, flame retardants, etc.), etc.

[0077] The average thickness of the thermally conductive particle-containing layer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 5 μm or more and 500 μm or less, and more preferably 20 μm or more and 200 μm or less.

[0078] In the laminate, the ratio of the void area at the interface between the metal layer and at least one of the first base material and the second base material is preferably 50% or less, and more preferably 30% or less. Since the laminate has a metal layer, the thermal resistance can be reduced, and if the void area ratio is 50%, significant heat conduction to the metal layer can be achieved, thereby achieving high thermal conductivity. The ratio of the void area at the interface between the metal layer and at least one of the first base material and the second base material can be determined, for example, as follows. For a laminate having a metal layer with an average thickness of 100 μm between a 30 mm × 30 mm × 2 mm Si substrate and a 30 mm × 30 mm × 2 mm glass substrate, an image 1 of the void at the interface between the glass substrate and the metal layer is taken from the glass substrate side using an optical microscope (manufactured by Olympus Corporation, product name: MX63). Image 2 of the gap at the interface between the Si substrate and the metal layer is taken from the Si substrate side using an infrared microscope (Olympus Corporation, product name: MX63 and Hamamatsu Photonics K.K., product name: InGaAs Camera C12741-03). The void area ratio (%) is calculated for the obtained interface void image 1 and void image 2 as follows. Using Microsoft Excel, the image is binarized at 50% black and white (threshold 128) and saved as a bitmap image. Next, the created binarized bitmap image is loaded into Excel as binary data, the number of pixels in the entire image and the number of pixels in the white parts are obtained, and the void area percentage (%) is calculated by counting the number of pixels in the white parts / the total number of pixels. Note that the void area percentage (%) may be evaluated for each of void image 1 (glass substrate) and void image 2 (Si substrate), or the value with the larger void area percentage may be used for evaluation.

[0079] Here, an embodiment of the laminate will be described in detail with reference to the drawings. In each drawing, the same components are denoted by the same reference numerals, and duplicated descriptions may be omitted. Furthermore, the number, position, shape, etc. of the following components are not limited to the present embodiment, and may be any number, position, shape, etc. that is preferable for implementing the present invention.

[0080] FIG. 1 is a schematic view showing an example of a laminate according to this embodiment, and FIG. 2 is a schematic view showing another example of a laminate according to this embodiment. 1 has, in this order, a first bonding layer 111, a metal layer 12, and a second bonding layer 112. The metal layer 12 has a recess 13 (131) on a first surface facing the first bonding layer 111 and a recess 13 (132) on a second surface facing the second bonding layer 112, and the recess 13 communicates with the outer periphery of the metal layer 12. The first bonding layer 111 and the second bonding layer 112 are sheet-shaped low-melting-point metal layers, and do not block the recesses 13 of the metal layer 12 during bonding, thereby suitably suppressing the occurrence of voids.

[0081] The laminate 20 shown in Figure 2 is a laminate in which the laminate 10 shown in Figure 1 is bonded to a first substrate 21 and a second substrate 22, and has the first substrate 21, a first bonding layer 111, a metal layer 12, a second bonding layer 112, and the second substrate 22 in this order. The laminate 10 shown in Figure 1 is an embodiment in which the first surface of the metal layer 12 is not curved, and is suitable for cases in which the contact surface of the first base material 21 with the laminate 10 is flat, as shown in Figure 2, or for cases in which sufficient bonding is ensured by the thickness or amount of the first bonding layer 111 even if the contact surface of the first base material 21 has a convex shape.

[0082] 3 is the same as the laminate 10 shown in FIG. 1, except that the first bonding layer 111 has a cutout portion at a position corresponding to the recess 131 of the metal layer 12. Similarly, the second bonding layer 112 has a cutout portion at a position corresponding to the recess 132 of the metal layer 12. The first bonding layer 111 and the second bonding layer 112 may be low-melting point metal layers or may be thermally conductive particle-containing layers, which can more suitably suppress the occurrence of voids without blocking the recesses of the metal layers during bonding.

[0083] The laminate 40 shown in Fig. 4 is an embodiment in which the first surface of the metal layer 12 in the laminate 30 shown in Fig. 3 has a curved surface, and the first surface of the metal layer 12 has a concave shape with a radius of curvature R represented by the following formula (1). Fig. 5 is an explanatory diagram of the radius of curvature R of the metal layer 12 in Fig. 4. Formula (1): R=(x 2 +y 2 ) / 2 / y 5, in the formula (1), x represents the distance between the center c and the edge e on the first surface of the metal layer 12, and y represents the difference (Te-Tc) between the thickness Te of the edge e and the thickness Tc of the center c of the metal layer 12. The unit is mm. The laminate 40 shown in FIG. 4 is suitable for the case where the surface of the first base material 21 that comes into contact with the laminate 10 has a convex shape.

[0084] Here, FIG. 6 shows an example of a radial pattern of recesses in the metal layer, FIG. 7 shows an example of a grid pattern of recesses in the metal layer, and FIG. 8 shows an example of a linear pattern of recesses in the metal layer. Although FIG. 6 shows a radial pattern that is a combination of a circular pattern and a radial pattern centered on the center c of the metal layer, the pattern may be radial only. The shape of the recesses in the radial pattern, the grid pattern, and the linear pattern is, for example, a quadrangular prism, and the cross section of the recesses is substantially quadrangular. Compared to a linear pattern, a grid pattern has contact points in multiple directions, allowing volatile components to move in multiple directions and easily escape from the system, which is preferable. Furthermore, in a radial pattern, when heating and bonding proceed from the center of the laminate toward the edge during bonding, the volatile components are sequentially volatilized and discharged from the center toward the edge, and then the recesses are filled with the bonding layer from the center toward the edge, resulting in excellent adhesion.

[0085] (Method of manufacturing laminate) The method for manufacturing the laminate of this embodiment includes a recess forming step and a bonding layer forming step, and may include a bonding step, and further includes other steps as necessary.

[0086] <Recess formation process> The recess forming step is a step of forming recesses on the first surface and the second surface of the metal layer, the recesses communicating with the outer periphery of the metal layer. The shapes of the metal layer and the recesses can be appropriately selected from the items explained above regarding the metal layer in the laminate of this embodiment.

[0087] Examples of methods for forming a pattern consisting of recesses in the metal layer include a method in which a recess shape pattern is formed by directly etching the metal layer; and a method in which a recess shape pattern is formed on the metal layer by photolithography, a metal (e.g., copper) is deposited by electrolytic plating, and the resist pattern is removed to form a pattern on the surface of the metal layer.

[0088] <Joining layer formation process> The bonding layer forming step is a step of forming a first bonding layer and a second bonding layer on the first surface and the second surface of the metal layer having the recess. The bonding layer can be appropriately selected from the items described above for the bonding layer in the laminate of this embodiment.

[0089] The method for forming the bonding layer on the metal layer having the recesses is not particularly limited and can be appropriately selected depending on the purpose. For example, the following methods (1) and (2) can be mentioned. (1) A method of forming a bonding layer by transferring a bonding layer provided on a transfer substrate (2) A method of forming a bonding layer, which is a layer containing thermally conductive particles, by applying a thermally conductive composition containing thermally conductive particles.

[0090] [Aspect in which the bonding layer has a notch] When the bonding layer has a cutout portion, the method for forming the bonding layer on the metal layer having the recess is not particularly limited and can be selected appropriately depending on the purpose, for example, the following methods (1-1), (1-2), and (2-1) can be mentioned. (1-1) As shown in FIGS. 9 and 10, a sheet-like bonding layer provided on a transfer substrate 31 is embossed or punched to form a bonding layer 11 having a cutout portion (FIG. 9), and then transferred onto a metal layer 12 having a recess to form a bonding layer 11 having a cutout portion (FIG. 10).

[0091] (1-2) As shown in FIGS. 11 and 12, the metal layer 12 having the recesses is pressed against the sheet-like bonding layer 11 provided on the transfer substrate 31 in the direction of the arrow in the figure (FIG. 11), thereby transferring the bonding layer 11 onto the metal layer 12 having the recesses to form the bonding layer 11 having the notches (FIG. 12).

[0092] (2-1) As shown in FIGS. 13-14 and 12, a spacer 32 having the shape of the recess 13 of the metal layer 12 and the total thickness of the recess 13 and the bonding layer 11 is provided in the recess 13 of the metal layer 12 (FIG. 13), and a thermally conductive composition containing thermally conductive particles is applied to form the bonding layer 11, which is a thermally conductive particle-containing layer (FIGS. 14 and 12).

[0093] [Metal layer having a curved surface] When the metal layer has a curved surface, the method for forming a bonding layer on the metal layer having the recess is not particularly limited and can be selected appropriately depending on the purpose, for example, the following methods (1-3), (1-4), and (2-2) can be mentioned. (1-3) As shown in Figures 9 and 15-16, the bonding layer 11 (Figure 9) having a cutout portion provided on the transfer substrate 31 is transferred onto the metal layer 12 having a recess using a pressing jig 33 having a convex curvature radius corresponding to the curvature radius R (Figure 15), and the bonding layer 11 having a cutout portion is formed on the metal layer 12 having the recess (Figure 16).

[0094] (1-4) As shown in Figures 17 and 16, the sheet-like bonding layer 11 provided on the transfer substrate 31 is transferred onto the metal layer 12 having the recesses using a pressing jig 33 having a convex curvature radius corresponding to the curvature radius R (Figure 17), and the bonding layer 11 having the notch portion is formed on the metal layer 12 having the recesses (Figure 18). Although an example of transferring a bonding layer 11 having a cutout portion has been described, a sheet-like bonding layer 11 may also be formed on the metal layer 12, and this can be achieved by appropriately adjusting conditions such as the type of transfer substrate 31, the type of bonding layer 11, and the pressing strength of the pressing jig 33.

[0095] (2-2) As shown in FIGS. 18-19 and 16, a spacer 32 having the shape of the recess 13 of the metal layer 12 and the total thickness of the recess 13 and the bonding layer 11 is provided in the recess 13 of the metal layer 12 (FIG. 18), and a thermally conductive composition containing thermally conductive particles is applied to form a bonding layer, which is a layer containing thermally conductive particles (FIGS. 19 and 16).

[0096] The thermally conductive particle-containing layer can be produced, for example, by applying a thermally conductive composition containing a curing component, a curing agent for curing the curing component, thermally conductive particles, and low-melting-point metal particles onto the metal layer and curing the composition. Examples of methods for applying the thermally conductive composition include inkjet coating, blade coating, gravure coating, gravure offset coating, bar coating, roll coating, knife coating, air knife coating, comma coating, U comma coating, AKKU coating, smoothing coating, microgravure coating, reverse roll coating, four-roll coating, five-roll coating, dip coating, curtain coating, slide coating, and die coating.

[0097] <Joining process> The bonding step is a step of placing either the first base material or the second base material on the bonding layer of the laminate and bonding them by heating, thereby making it possible to suitably manufacture a laminate further including either the first base material or the second base material. In the bonding step, the laminate is preferably disposed between the first base material and the second base material, and the laminate is heated to bond the first and second base materials.

[0098] The heating conditions in the bonding step are not particularly limited as long as they are temperature conditions above the melting point of the low-melting point metal contained in the bonding layer or above the sintering temperature of the thermally conductive particles contained in the thermally conductive particle-containing layer, and can be selected appropriately depending on the purpose. For example, if the melting point of the low-melting point metal is mp, then a temperature of mp+1°C or higher and mp+20°C or lower for 1 to 30 minutes is preferred, and a temperature of mp+3°C or higher and mp+10°C or lower for 1 to 10 minutes is more preferred.

[0099] The laminate of this embodiment can be suitably used, for example, when forming a power LED module or a power IC module by bonding a thermal interface material (TIM), which fills the minute gap between a heat source such as an LSI and a heat sink, and a heat dissipation substrate on which an LED chip or an IC chip is mounted, to a heat sink, thereby allowing heat to flow smoothly between the two. Here, the power LED module is available in a wire bonding mounting type and a flip chip mounting type, and the power IC module is available in a wire bonding mounting type.

[0100] (heat dissipation structure) The heat dissipation structure of this embodiment includes a heat generating element, the laminate of this embodiment, and a heat dissipation member, and may further include other members as necessary.

[0101] The heating element is not particularly limited and can be appropriately selected depending on the purpose. Examples include electronic components such as a CPU (Central Processing Unit), an MPU (Micro Processing Unit), and a GPU (Graphics Processing Unit).

[0102] The heat dissipation member is not particularly limited as long as it is a structure that dissipates heat generated by electronic components (heat generating elements), and can be appropriately selected depending on the purpose. Examples include a heat spreader, a heat sink, a vapor chamber, and a heat pipe. The heat spreader is a member for efficiently transferring heat from the electronic component to other components. The material of the heat spreader is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include copper and aluminum. The heat spreader is usually in a flat plate shape. The heat sink is a member for releasing heat from the electronic component into the air. The material of the heat sink is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include copper and aluminum. The heat sink has, for example, a plurality of fins. The heat sink has, for example, a base portion and a plurality of fins extending in a non-parallel direction (for example, a direction perpendicular to) one surface of the base portion. The heat spreader and the heat sink are generally solid structures with no internal voids. The vapor chamber is a hollow structure. A volatile liquid is sealed in the internal space of the hollow structure. Examples of the vapor chamber include a hollow heat spreader and a hollow plate-like structure similar to the heat sink. The heat pipe is a hollow structure having a cylindrical, approximately cylindrical, or flattened cylindrical shape, and a volatile liquid is sealed in the internal space of the hollow structure.

[0103] 20 is a schematic cross-sectional view showing an example of a semiconductor device as a heat dissipation structure. The laminate 7 of this embodiment dissipates heat generated by an electronic component 3 such as a semiconductor element, and as shown in FIG. 20, is fixed to a main surface 2a of the heat spreader 2 that faces the electronic component 3, and is sandwiched between the electronic component 3 and the heat spreader 2. In addition, the thermally conductive sheet 1 is sandwiched between the heat spreader 2 and a heat sink 5.

[0104] The heat spreader 2 is formed, for example, in the shape of a rectangular plate, and has a main surface 2a facing the electronic component 3 and side walls 2b erected along the outer periphery of the main surface 2a. The heat spreader 2 has a thermally conductive sheet 1 provided on the main surface 2a surrounded by the side walls 2b, and a heat sink 5 provided on the other surface 2c opposite the main surface 2a via the thermally conductive sheet 1. The higher the thermal conductivity of the heat spreader 2, the lower the thermal resistance and the more efficiently it absorbs heat from the electronic component 3 such as a semiconductor element, so the heat spreader 2 can be made of, for example, copper or aluminum, which have good thermal conductivity.

[0105] The electronic component 3 is, for example, a semiconductor element such as an LSI, and is mounted on the wiring board 6. The tip surface of the side wall 2b of the heat spreader 2 is also mounted on the wiring board 6, so that the side wall 2b surrounds the electronic component 3 at a predetermined distance. Then, by providing the laminate 7 of this embodiment on the main surface 2a of the heat spreader 2, a heat dissipation member that absorbs heat generated by the electronic components 3 and dissipates the heat from the heat sink 5 is formed. [Industrial Applicability]

[0106] The laminate of this embodiment can achieve high thermal conductivity as a thermal interface material (TIM), and is therefore suitable for use in, for example, areas surrounding various electrical devices such as CPUs, MPUs, power transistors, LEDs, and laser diodes, where temperature can adversely affect the efficiency and lifespan of element operation. [Explanation of symbols]

[0107] 1. Thermal conductive sheet 2 heat spreaders 2a Main surface 3 Heat generating elements (electronic components) 3a Top side 5 Heatsink 6. Wiring board 7 Laminate 10, 20, 30, 40 laminates 11 Bonding layer 111 First bonding layer 112 Second bonding layer 12 metal layer 13 Recess 131 Recess on first surface 132 Recess on second surface 21 First substrate 22 Second substrate 31 Transfer substrate 32 spacer 33 Pushing jig

Claims

1. a first bonding layer, a metal layer, and a second bonding layer in this order; A laminate characterized in that the metal layer has a recess on a first surface on the side of the first bonding layer and a second surface on the side of the second bonding layer, the recess communicating with the outer periphery of the metal layer.

2. 2. The laminate according to claim 1, wherein the depth of the recess is 1 μm or more.

3. The laminate according to claim 1 , wherein the recesses have at least one of a radial, lattice, linear, and embossed pattern.

4. The laminate according to claim 1 , wherein the metal layer contains at least one selected from the group consisting of Cu, Al, Ag, Au, Fe, and Pt.

5. The laminate according to claim 1 , wherein the first bonding layer and the second bonding layer have cutouts at locations corresponding to the recesses in the metal layer.

6. the first surface of the metal layer has a concave shape with a radius of curvature R expressed by the following formula (1), 2. The laminate according to claim 1, wherein the radius of curvature R is 500 mm or more and 5000 mm or less. Formula (1): R=(x ２ +y ２ ) / 2 / y In the formula (1), x represents the distance between the center c and the end e on the first surface of the metal layer, and y represents the difference (Te-Tc) between the thickness Te of the end e and the thickness Tc of the center c on the metal layer.

7. The laminate according to claim 1 , wherein the first bonding layer and / or the second bonding layer is a low-melting-point metal layer containing a low-melting-point metal.

8. 8. The laminate according to claim 7, wherein the low-melting-point metal is at least one selected from the group consisting of In, Ga, Sn, Zn, and Bi.

9. 8. The laminate according to claim 7, wherein the low melting point metal is at least one selected from the group consisting of Sn—Pb solder, Pb—Sn—Sb solder, Sn—Sb solder, Sn—Pb—Bi solder, Sn—Bi solder, Sn—Bi—Ag solder, Sn—Cu solder, Sn—Pb—Cu solder, Sn—In solder, Sn—Ag solder, Sn—Pb—Ag solder, Pb—Ag solder, and Sn—Ag—Cu solder.

10. The laminate according to claim 7 , further comprising a polyfunctional carboxylic acid layer containing a trifunctional or higher polyfunctional carboxylic acid on the low-melting point metal layer.

11. The laminate according to claim 1 , wherein the first bonding layer and / or the second bonding layer is a thermally conductive particle-containing layer containing thermally conductive particles.

12. a recess forming step of forming recesses on the first surface and the second surface of the metal layer, the recesses communicating with the outer periphery of the metal layer; a bonding layer forming step of forming a first bonding layer and a second bonding layer on the first surface and the second surface of the metal layer having the recess; A method for producing a laminate, comprising:

13. The method for producing a laminate according to claim 12 , wherein the bonding layer forming step is a step of forming a bonding layer by transferring a bonding layer provided on a transfer substrate onto the metal layer having the recesses.

14. the first surface of the metal layer has a concave shape with a radius of curvature R expressed by the following formula (1), The method for producing a laminate according to claim 12, wherein the radius of curvature R is 500 mm or more and 5000 mm or less. Formula (1): R=(x ２ +y ２ ) / 2 / y In the formula (1), x represents the distance between the center c and the end e on the first surface of the metal layer, and y represents the difference (Te-Tc) between the thickness Te of the end e and the thickness Tc of the center c of the metal layer.

15. 15. The method for manufacturing a laminate according to claim 14, wherein the bonding layer forming step is a step of transferring a bonding layer provided on a transfer substrate using a pressing jig having a convex radius of curvature corresponding to the radius of curvature R to form a bonding layer.

16. The method for manufacturing a laminate according to claim 12 , wherein the first bonding layer and the second bonding layer have cutouts at locations corresponding to the recesses in the metal layer.

17. 17. The method for manufacturing a laminate according to claim 16, wherein the bonding layer forming step is a step of providing a spacer having the shape of the recess of the metal layer and the total thickness of the recess and the bonding layer in the recess of the metal layer, and applying a thermally conductive composition containing thermally conductive particles to form a thermally conductive particle-containing layer.

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