Laminated body and laminated body manufacturing method

Abstract

To provide a laminated body capable of acquiring an excellent adhesion between a metal plate and a silicon substrate and having an excellent thermal conductivity.SOLUTION: A laminated body has a low melting metal layer made of a low melting metal and a polyfunctional carboxylic acid layer containing the polyfunctional carboxylic acid with three or more functions on the low melting metal layer, in which the polyfunctional carboxylic acid content per area of the polyfunctional carboxylic acid layer is 0.002 μg / mm2 or more and 0.5 μg / mm2 or less.SELECTED DRAWING: Figure 1

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) and other electronic devices, prolonged exposure to high temperatures due to heat generated by the elements used can lead to malfunctions or breakdowns. For this reason, thermally conductive materials are widely used to prevent LSIs and other devices from overheating. These thermally conductive materials can prevent the temperature of the device from rising by diffusing the heat generated by the elements or by transferring it to a heat dissipation member that releases the heat outside the system, such as to the atmosphere.

[0003] For example, a flux containing rosin, an organic acid, a solvent (S), and an alkanolamine has been reported, in order to provide a flux that can be suitably used for mounting indium sheets, has high wettability even in bonding at relatively low temperatures, and has an improved ability to suppress void generation, wherein the organic acid contains a monocarboxylic acid (A1) having a melting point of 35°C or more and 90°C or less and a molecular weight of 180 or more and 350 or less, and the solvent (S) contains a solvent (S1) having a boiling point of 100°C or less, and the content of each component is within a specific range (see, for example, Non-Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7239865 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the conventional technology described in Non-Patent Document 1 does not provide sufficient adhesion to the metal plate or silicon substrate, which not only generates thermal resistance but also leads to insufficient formation of a thermal path, making it difficult to obtain high thermal conductivity.

[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 obtain excellent adhesion to a metal plate or a silicon substrate and has excellent thermal conductivity. [Means for solving the problem]

[0007] The means for solving the above problems are as follows: <1> a low-melting-point metal layer made of a low-melting-point metal; a multifunctional carboxylic acid layer containing a trifunctional or higher polyfunctional carboxylic acid on the low-melting point metal layer, 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 The laminate is characterized in that: <2> The low melting point metal includes at least one selected from the group consisting of Ga, Sn, Zn, Bi, and In. <1> 1. The laminate according to claim 1. <3> The polyfunctional carboxylic acid is represented by the following general formula (I): <1> or <2> 1. The laminate according to claim 1. [ka] In the general formula (1), R1 to R3 each independently represent an alkylene group or a lactone skeleton, R4 represents a hydrogen atom or an alkyl group which may be 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. <4> The low-melting-point metal layer, the polyfunctional carboxylic acid layer, and either a silicon substrate or an opposing substrate on the polyfunctional carboxylic acid layer in this order. <1> from <3> The laminate according to any one of the above items. <5> a first multifunctional carboxylic acid layer on a first surface of the low-melting point metal layer, and a second multifunctional carboxylic acid layer on a second surface of the low-melting point metal layer opposite to the first surface; The above-mentioned substrate has a silicon substrate, the first multifunctional carboxylic acid layer, the low-melting point metal layer, the second multifunctional carboxylic acid layer, and an opposing substrate in this order. <1> from <4> The laminate according to any one of the above items. <6> The opposing substrate contains one or more selected from the group consisting of Cu, Ag, Au, and Pt. <5> 1. The laminate according to claim 1. <7> The silicon substrate has a metal layer on the side of the first polyfunctional carboxylic acid layer. <5> or <6> 1. The laminate according to claim 1. <8> The thermal conductivity is 30W / (m·K) or more. <5> from <7> The laminate according to any one of the above items. <9> The method includes a step of applying a trifunctional or higher polyfunctional carboxylic acid onto a low-melting-point metal layer made of a low-melting-point metal, The amount of the polyfunctional carboxylic acid added per area is 0.002 μg / mm 2 More than 0.5μg / mm 2 The method for producing a laminate is characterized by the following. <10> The method further comprises a step of placing one of a silicon substrate and an opposing substrate on the low-melting-point metal layer via the polyfunctional carboxylic acid, and melting and solidifying the low-melting-point metal. <9> 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 having excellent adhesion to a metal plate or a silicon substrate and excellent thermal conductivity can be provided. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing an example of a laminate according to this embodiment. [Figure 2] FIG. 2 is a schematic diagram showing another example of the laminate according to this embodiment. [Figure 3] FIG. 3 is a schematic diagram showing another example of the laminate according to this embodiment. [Figure 4] FIG. 4 is a schematic diagram showing another example of the laminate according to this embodiment. [Figure 5] FIG. 5 is a schematic diagram showing another example of the laminate according to this embodiment. [Figure 6] FIG. 6 is a schematic diagram showing another example of the laminate according to this embodiment. [Figure 7] FIG. 7 is a schematic cross-sectional view showing an example of a heat dissipation structure having the laminate of this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Laminate) The laminate of this embodiment has a low-melting-point metal layer and a polyfunctional carboxylic acid layer, and may further have a silicon substrate, an opposing substrate, and other members as necessary. 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 The following is the result.

[0011] After extensive research, the inventors have found that by using a laminate having a multifunctional carboxylic acid layer containing a trifunctional or higher functional multifunctional carboxylic acid on a low-melting point metal layer, it is possible to achieve both good adhesion to metal plates and silicon substrates and good thermal conductivity.

[0012] The laminate of this embodiment can effectively remove oxides of low-melting-point metals, obtain excellent adhesion to metal plates and silicon substrates, reduce contact resistance with metal plates and silicon substrates, and achieve excellent thermal conductivity and adhesion. The laminate can achieve a thermal conductivity of 20 W / (m·K) or more, preferably 30 W / (m·K) or more, and more preferably 40 W / (m·K) or more. It is known that when the contact surface between the substrate and the metal is oxidized, surface roughness and thermal resistance occur, resulting in a decrease in thermal conductivity, and carboxylic acid can remove low-melting-point metal oxides according to the following reaction formula: From the examples described below, it is inferred that the presence of a polyfunctional carboxylic acid layer can achieve excellent thermal conductivity and adhesion, thereby removing low-melting-point metal oxides. Oxide of low-melting metal + carboxylic acid → low-melting metal + reaction product with carboxylic acid + water

[0013] <Low melting point metal layer> The low-melting-point metal layer is a layer made of a low-melting-point metal. The low-melting-point metal is a general term for lead (melting point: 327.5°C) and metals having a melting point of 327.5°C or lower. The low-melting-point metal is not particularly limited and can be appropriately selected depending on the purpose, and examples include metals such as Ga, Sn, Zn, Bi, and In; and alloys containing these metals. These may be used alone or in combination of two or more. Among these, In is preferred from the viewpoints of lower hardness than other metal elements, high conformability to the surfaces of the substrate and the opposing substrate (specifically, the die and the lid), and high adhesion.

[0014] The low-melting-point metal layer may be formed into a sheet 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) or an indium sheet (product name: Indium sheet, manufactured by Axis Co., Ltd., average thickness: 100 μm).

[0015] 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 heating step in the method for producing a laminate of this embodiment, which will be described later.

[0016] The average thickness of the low melting point metal is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 20 μm or more and 1000 μm or less, and more preferably 50 μm or more and 200 μm or less.

[0017] <Multifunctional carboxylic acid layer> The polyfunctional carboxylic acid layer is a layer containing a trifunctional or higher polyfunctional carboxylic acid, and 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 or less, 0.005 μg / mm 2 More than 0.2μg / mm 2 Preferably less than 0.01 μg / mm 2 More than 0.1μg / mm 2 The following is more preferred:

[0018] -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.

[0019] [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.

[0020] 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.

[0021] 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).

[0022] [ka] In the general formula (i), n represents an integer of 1 or more, preferably 1 to 10.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] [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.

[0027] 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.

[0028] 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.

[0029] 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).

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.).

[0034] [Other aspects of the laminate] The laminate may further include either a silicon substrate or an opposing substrate, or may further include a silicon substrate and an opposing substrate. One embodiment of the laminate includes the low-melting point metal layer, the polyfunctional carboxylic acid layer, and either a silicon substrate or an opposing substrate on the polyfunctional carboxylic acid layer, in this order. Another embodiment of the laminate has a first multifunctional carboxylic acid layer on a first surface of the low-melting point metal layer and a second multifunctional carboxylic acid layer on a second surface of the low-melting point metal layer opposite the first surface, and has a silicon substrate, the first multifunctional carboxylic acid layer, the low-melting point metal layer, the second multifunctional carboxylic acid layer, and an opposing substrate, in this order.

[0035] <Silicon substrate> The shape, structure, size, material, etc. of the silicon substrate are not particularly limited and can be appropriately selected depending on the purpose. Examples of the shape of the substrate include a plate shape, a sheet shape, etc. Examples of the structure of the substrate include a single-layer structure, a laminated structure, etc. The size of the substrate can be appropriately selected depending on the application, etc. The average thickness of the silicon substrate is not particularly limited and can be appropriately selected depending on the purpose.

[0036] The silicon substrate may be the heat generating element (electronic component, silicon substrate called a die or chip) itself in the heat dissipation structure, and any metal can be formed by sputtering during the manufacturing process. The silicon substrate preferably has a metal layer on the polyfunctional carboxylic acid layer side or the first polyfunctional carboxylic acid layer side, and a metal layer in which Ti / Ni / Au are stacked from the silicon substrate side is more preferred from the viewpoints of adhesion and stability.

[0037] <<Metal layer>> The metal layer is preferably formed on the silicon substrate on the side of the polyfunctional carboxylic acid layer, and is formed in contact with the silicon substrate. The metal layer has at least a seed layer, preferably further has a barrier layer, and more preferably further has a top layer. Specifically, the metal layer may be a seed layer, a layer in which a seed layer and a barrier layer are stacked in this order from the silicon substrate side, a layered structure in which a seed layer, a barrier layer, and a top layer are stacked, or a layer in which a seed layer and a top layer are stacked. Any of these modes can be appropriately selected depending on the purpose.

[0038] The average thickness of the metal layer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 0.1 μm or more and 5 μm or less, and more preferably 0.2 μm or more and 2 μm or less.

[0039] -Seed layer- The seed layer contains at least one of Ti, W, Al, Mo, and Cr, and these may be used alone or in combination of two or more. Among these, Ti, W, etc. are preferred from the viewpoints of adhesion to the silicon substrate, hardness, and thermal conductivity, and Ti is more preferred. The seed layer may be a single layer of a single metal or alloy, or may be a laminate thereof. The seed layer may also contain a metal silicide of silicon in the silicon substrate and at least one of Ti, W, Al, Mo, and Cr, which is preferable in that the inclusion of the metal silicide improves adhesion to the silicon substrate and reduces contact resistance with the silicon substrate.

[0040] The average thickness of the seed layer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 0.05 μm or more and 0.5 μm or less, and more preferably 0.1 μm or more and 0.2 μm or less.

[0041] -Barrier layer- The barrier layer contains at least one of Ni, Al, Mo, Nb, TiN, TaN, and WN, and these may be used alone or in combination of two or more. Among these, Ni, Nb, etc. are preferred from the viewpoints of adhesion to the heat conductive layer, hardness, and thermal conductivity, and Ni is more preferred. The barrier layer may be a single layer of a single metal or alloy, or may be a laminate thereof.

[0042] The average thickness of the metal layer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 0.05 μm or more and 0.5 μm or less, and more preferably 0.1 μm or more and 0.3 μm or less.

[0043] -Top Tier- The top layer contains at least one of Ag, Au, Cu, Pd, and Pt, and these may be used alone or in combination of two or more. Among these, Ag, Au and the like are preferred, and Au is more preferred, from the viewpoints of adhesion to the thermally conductive layer, the antioxidant effect of the barrier layer, hardness, and thermal conductivity. The top layer may be a single layer of a single metal or alloy, or may be a laminate thereof.

[0044] The average thickness of the metal layer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 0.1 μm or more and 2 μm or less, and more preferably 0.2 μm or more and 1 μm or less.

[0045] <Facing substrate> The opposing substrate is disposed opposite the 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 opposing substrate include a plate shape, a sheet shape, etc. Examples of the structure of the opposing substrate include a single-layer structure, a laminated structure, etc. The size of the opposing substrate can be appropriately selected depending on the application, etc. Examples of the material for the opposing substrate include metals such as Cu, Ag, Au, and Pt; alloys containing these metals; and the like. These may be used alone or in combination of two or more. Among these, Cu is preferred from the viewpoints of thermal conductivity, moldability, and economy, and in a specific embodiment, it is preferred to apply metal plating, with Ni-plated Cu being preferred.

[0046] The average thickness of the opposing substrate is not particularly limited and can be appropriately selected depending on the purpose. The opposing base material may be a lid or a heat spreader itself in a heat dissipation structure.

[0047] <Other materials> The other members are not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include a protective layer.

[0048] 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.

[0049] 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. The laminate 10 shown in FIG. 1 has a polyfunctional carboxylic acid layer 12 on a low-melting point metal layer 11. The laminate 20 shown in FIG. 2 has polyfunctional carboxylic acid layers 12a and 12b on both sides of a low-melting point metal layer 11.

[0050] 3 to 5 are schematic diagrams showing other examples of the laminate according to this embodiment. Specifically, the laminate may further include a substrate, and may include a silicon substrate 13 on one surface of a low-melting-point metal layer 11 via a polyfunctional carboxylic acid layer 12 (see FIG. 3), a counter substrate 15 on one surface of the low-melting-point metal layer 11 via a polyfunctional carboxylic acid layer 12 (see FIG. 4), or a laminate including a silicon substrate 13 and a counter substrate 15, in which, from the silicon substrate 13 side, a polyfunctional carboxylic acid layer 12a, a low-melting-point metal layer 11, a polyfunctional carboxylic acid layer 12b, and a counter substrate 15 are stacked (see FIG. 5). Any of these modes can be appropriately selected depending on the purpose.

[0051] 6 is a schematic diagram showing another example of the laminate according to this embodiment. The silicon substrate 13 may further have a metal layer 14 on the polyfunctional carboxylic acid layer 12 side. The metal layer 14 may be formed of a seed layer, or may be a laminate in which a seed layer and a barrier layer are laminated in this order from the silicon substrate 13 side, or may be a laminate in which a seed layer, a barrier layer, and a top layer are laminated in this order from the silicon substrate 13 side, or may be a laminate in which a seed layer and a top layer are laminated in this order from the silicon substrate 13 side. Any of these modes can be appropriately selected depending on the purpose.

[0052] The method for manufacturing a laminate of this embodiment, which will be described later, can provide excellent adhesion to a metal plate or a silicon substrate, and can suitably manufacture a laminate with excellent thermal conductivity. 3 to 6, if the low-melting-point metal layer 11 in the laminate as shown in Figures 3 to 6 lifts or peels off from the silicon substrate 13 and / or the opposing substrate 15, or if voids occur, the adhesion to the substrate may decrease, and the reliability of the laminate may be impaired. In this embodiment, by having the polyfunctional carboxylic acid layer 12, the adhesion between the low-melting-point metal layer 11 and the silicon substrate 13 and / or the opposing substrate 15 is excellent, and therefore a laminate with excellent thermal conductivity can be provided.

[0053] Methods for confirming that the laminate has adhesion include: using an ultrasonic imaging system (SAT) to evaluate the laminate after compression for lifting, peeling, and the presence of voids; using an ultrasonic imaging system (SAT) to evaluate the laminate after compression for adhesion to the substrate and the presence of voids after an accelerated life test (e.g., 130°C, 85% humidity, 192 hours); indirectly estimating the adhesion to the substrate and the presence of voids by comparing the ratio (%) of the thermal conductivity of the manufactured laminate to the thermal conductivity of the low-melting point metal layer used; and combinations of these methods.

[0054] A specific method for confirming that the laminate contains the polyfunctional carboxylic acid layer is to analyze components present at the interface between the low-melting-point metal layer 11 and the silicon substrate 13 and / or the opposing substrate 15 by FT-IR measurement, and identify the polyfunctional carboxylic acid or a component derived from the polyfunctional carboxylic acid. First, the silicon substrate 13 and / or the opposing substrate 15 are measured by the ATR method as a comparison. Next, the laminate is peeled apart to separate the silicon substrate 13 and the opposing substrate 15, and the interface with the low-melting-point metal layer 11 is measured by the ATR method. Next, the difference spectrum between each of the obtained spectra and the spectrum of the silicon substrate 13 and / or the opposing substrate 15 is calculated. It is confirmed whether this difference spectrum is the polyfunctional carboxylic acid or a component derived from the polyfunctional carboxylic acid. FT-IR measurements can be performed using, for example, a Nicolet iS10 (manufactured by Thermo Fisher Scientific Inc.) by the ATR method.

[0055] (Method of manufacturing laminate) The method for producing a laminate of the present embodiment includes a polyfunctional carboxylic acid providing step, and in one aspect, preferably includes a substrate disposing step and a heating step, and may include a metal layer forming step, and further includes other steps as necessary. This makes it possible to obtain excellent adhesion to the metal plate or silicon substrate, and to manufacture a laminate with excellent thermal conductivity, thereby making it possible to suitably manufacture the laminate of this embodiment.

[0056] <Polyfunctional Carboxylic Acid Addition Step> The polyfunctional carboxylic acid applying step is a step of applying the polyfunctional carboxylic acid onto the low-melting point metal layer. The amount of the polyfunctional carboxylic acid applied per area of ​​the polyfunctional carboxylic acid layer is 0.002 μg / mm 2 More than 0.5μg / mm 2 or less, 0.005 μg / mm 2 More than 0.2μg / mm 2 Preferably less than 0.01 μg / mm 2 More than 0.1μg / mm 2 The following is more preferred:

[0057] The method for applying the polyfunctional carboxylic acid may be to apply a solution containing the polyfunctional carboxylic acid, and examples thereof include spin coating, 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.

[0058] -Polyfunctional carboxylic acid- The polyfunctional carboxylic acid can be appropriately selected from the items explained in the laminate of the present embodiment.

[0059] The solvent in the solution is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include:

[0060] The content of the polyfunctional carboxylic acid in the solution is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 0.1% by mass or more and 1% by mass or less with respect to the total amount of the solution.

[0061] <Base material placement process> The substrate placement step is a step of placing either a silicon substrate or an opposing substrate on the low-melting-point metal layer via the polyfunctional carboxylic acid. The method of disposing may be such that either the silicon substrate or the opposing substrate is disposed on the low-melting point metal layer via the polyfunctional carboxylic acid, or (1) after applying the polyfunctional carboxylic acid on the low-melting point metal layer, either the silicon substrate or the opposing substrate is disposed via the polyfunctional carboxylic acid, or (2) after applying the polyfunctional carboxylic acid on the low-melting point metal layer, either the silicon substrate or the opposing substrate is disposed via the polyfunctional carboxylic acid,

[0062] <Heating process> The heating step is a step of heating the laminate obtained in the substrate placement step to melt and solidify the low-melting point metal, thereby making it possible to suitably manufacture a laminate further having either a silicon substrate or an opposing substrate.

[0063] The heating conditions are not particularly limited as long as the temperature is equal to or higher than the melting point of the low-melting-point metal, and can be appropriately selected depending on the purpose. For example, if the melting point of the low-melting-point metal is mp, the heating conditions are preferably mp+1°C or higher and mp+20°C or lower for 1 to 30 minutes, and more preferably mp+3°C or higher and mp+10°C or lower for 1 to 10 minutes.

[0064] By placing a substrate on the low-melting point metal layer via the polyfunctional carboxylic acid and then performing a heating step, it is possible to improve the adhesion between either the silicon substrate or the opposing substrate and the low-melting point metal layer.

[0065] <Metal layer formation process> The metal layer forming step is a step of forming a metal layer having a seed layer containing at least one of Ti, W, Al, Mo, and Cr on a silicon substrate. The metal layer has at least a seed layer, preferably further has a barrier layer, and more preferably further has a top layer. The seed layer, barrier layer, and top layer may be appropriately selected from those described in the laminate of this embodiment.

[0066] The method for forming the metal layer on the silicon substrate is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include physical vapor deposition methods (PVD, physical vapor deposition methods) such as sputtering, vacuum deposition, and ion plating; chemical vapor deposition methods (CVD methods) such as thermal chemical vapor deposition (thermal CVD), plasma CVD, and atomic layer deposition (ALD); etc. Among these, sputtering is preferred.

[0067] -Silicon substrate- The silicon substrate can be appropriately selected from the items explained in the laminate of this embodiment.

[0068] <Other processes> The other steps are not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include a protective layer forming step and an opposing substrate laminating step.

[0069] 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.

[0070] (heat dissipation structure) The heat dissipation structure of this embodiment includes a heat generating element, the laminate of this embodiment described above, and a heat dissipation member, and may further include other members as necessary.

[0071] 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).

[0072] 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.

[0073] 7 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. 7, is fixed to a main surface 2a of the heat spreader 2 facing the electronic component 3, and is sandwiched between the electronic component 3 and the heat spreader 2. The thermally conductive sheet 1 is sandwiched between the heat spreader 2 and a heat sink 5.

[0074] 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 extending along the 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. Therefore, the heat spreader 2 can be formed using, for example, copper or aluminum, which have good thermal conductivity.

[0075] The electronic component 3 is, for example, a semiconductor element such as a BGA, 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. [Example]

[0076] Examples of the present invention will be described below, but the present invention is not limited to these examples in any way.

[0077] Example 1 <Synthesis of polyfunctional carboxylic acids> 50 parts by mass of glycerin (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was weighed into a three-necked glass flask equipped with a thermocouple, a stirrer, a condenser, and a heating device, and 102.1 parts by mass of methyl ethyl ketone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added thereto and stirred thoroughly to completely dissolve.

[0078] Next, 2.4 parts by mass of triethylamine (Tokyo Chemical Industry Co., Ltd.) was added as a catalyst and further stirred thoroughly. After complete dissolution, 204.4 parts by mass of glutaric anhydride (Tokyo Chemical Industry Co., Ltd.) in powder form was added dropwise to the three-neck flask using a funnel. The temperature was kept constant at 60°C and stirred for 24 hours until the reaction was completely completed. After cooling to room temperature, the above-mentioned synthesis product was transferred to a recovery flask and concentrated using an evaporator. It was then dried under reduced pressure (60°C for 24 hours) to obtain the desired polyfunctional carboxylic acid in a 92% yield. The resulting polyfunctional carboxylic acid was in liquid form.

[0079] The resulting polyfunctional carboxylic acid was identified by FT-IR measurement. FT-IR measurement was performed using a Nicolet iS10 (manufactured by Thermo Fisher Scientific Co., Ltd.) by the ATR method. The FTIR absorption of the resulting polyfunctional carboxylic acid is shown below. -FTIR absorption of polyfunctional carboxylic acids- 781cm -1 , 868cm -1 , 1016cm -1 , 1065cm -1 , 1097cm -1 , 1138cm -1 , 1268cm -1 , 1410cm -1 , 1703cm -1 , 1730cm -1 and 2700 cm -1 ~3700cm -1 .

[0080] As a result of FTIR absorption, broad absorption vibrations derived from carboxylic acid were observed, and it was determined that the target compound was pentanedioic acid-1,1',1''-(1,2,3-propaneethyl) ester (molecular formula: C18 H 26 O 12 ) was found to be obtained. [ka]

[0081] <Production of laminate> The obtained polyfunctional carboxylic acid was dissolved in acetone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) to prepare a 0.2 mass% polyfunctional carboxylic acid solution, and the solution was applied to a silicon substrate (Φ8-inch wafer processed product, manufactured by Toshiba Business Expert Co., Ltd.) having a metal layer of 20 mm × 20 mm × 0.725 mm so that the amount of polyfunctional carboxylic acid applied per area was 0.02 μg / mm 2 Next, an indium sheet (4N In sheet, manufactured by Nippon Invest Co., Ltd., 20 mm x 20 mm, average thickness 100 μm) was placed on the silicon substrate as a low-melting-point metal layer via the polyfunctional carboxylic acid. The amount of polyfunctional carboxylic acid added per area was 0.02 μg / mm 2 A polyfunctional carboxylic acid was applied using a spin coater so that the thickness of the laminate was 1.0 mm, and a copper substrate (C1100 1.0 mm x 25 mm x 25 mm, manufactured by Engineering Test Services Co., Ltd.) measuring 25 mm x 25 mm x 1 mm was placed as an opposing substrate, with the polyfunctional carboxylic acid sandwiched between them. Both sides of the resulting laminate were sandwiched between 200 μm-thick silicone sheets, heated at 160° C. for 5 minutes to melt the low-melting-point metal, and then cooled to room temperature (RT) to solidify, producing the laminate of Example 1.

[0082] Next, the obtained laminate of Example 1 was evaluated for "total thickness of laminate," "thermal conductivity," and "adhesion" as follows. As a reference example, the same evaluation was carried out using only the indium sheet used in Example 1. The results are shown in Table 1.

[0083] <Measurement of total thickness of laminate> The total thickness of the laminate was measured using a thickness gauge (device name: Digimatic Thickness Gauge 547-301A, manufactured by Mitutoyo Corporation). Each laminate was cut, the resulting cut surface was polished, and the polished surface was photographed with a scanning electron microscope (S-3000N, manufactured by Hitachi, Ltd.). The thickness of each layer was measured from the cut surface of the laminate, and the average thickness was calculated at any three points. The results are shown in Tables 1 and 2. In the laminate of Example 1, the multifunctional carboxylic acid layer 12a and the multifunctional carboxylic acid layer 12b could not be confirmed by microscopic observation, corresponding to the cross-sectional view of the laminate shown in Figure 6. However, FT-IR measurement of the components on each side of the low-melting point metal layer 11 identified the presence of a multifunctional carboxylic acid.

[0084] <Thermal conductivity> The thermal conductivity of each laminate was measured in accordance with JIS R 1611 using a flash thermal diffusivity / thermal conductivity measuring device (LFA467, manufactured by Netsch Japan Co., Ltd.) with a pulse width of 20 μsec, and the thermal conductivity was evaluated according to the following criteria. [Evaluation criteria] ◎: Thermal conductivity is 30 W / m·K or higher. Good: Thermal conductivity is 20 W / m·K or more and less than 30 W / m·K. △: Thermal conductivity is 10 W / m·K or more and less than 20 W / m·K. ×: Thermal conductivity is less than 10 W / m·K.

[0085] <Adhesion> <<Preparation of laminated body after compression>> Each laminate was sandwiched between a 20mm x 20mm silicon plate (average thickness 0.77mm) and a 25mm x 25mm copper plate (average thickness 1.0mm) and pressed for 5 minutes using a mini press under the following conditions: upper plate temperature on the copper substrate side 160°C, lower plate temperature on the silicon substrate side 160°C, and set air pressure 0.0275MPa (10psi equivalent pressure).

[0086] <<Adhesion>> The laminate after compression bonding was observed using an ultrasonic imaging device (SAT, FS300IIIHR, manufactured by Hitachi Power Solutions Co., Ltd.) to check for lifting and peeling at the interface with the low-melting-point metal layer, and to evaluate the adhesion to the silicon substrate and the opposing substrate. A 50 MHz, 7 mm probe was used on the copper plate side, and a 25 MHz probe was used on the silicon plate side. [Evaluation criteria] ⊚: The low melting point metal layer was not lifted or peeled off from the substrate. ◯: The low-melting-point metal layer was lifted and / or peeled off from the substrate in less than 20% of the observed field of view, which is within the practical range. △: The low melting point metal layer was lifted and / or peeled off from the substrate in 20% or more and less than 80% of the observed field of view, which is outside the practical range. ×: The low-melting-point metal layer was lifted and / or peeled off from the substrate in 80% or more of the observed field of view, which is outside the practical range.

[0087] Example 2 In Example 1, the 0.2 mass % polyfunctional carboxylic acid solution was changed to a 1 mass % polyfunctional carboxylic acid solution, and the amount of polyfunctional carboxylic acid applied per area was 0.1 μg / mm 2 A laminate of Example 2 was produced in the same manner as in Example 1, except for the above change.

[0088] Example 3 In Example 1, the 0.2 mass % polyfunctional carboxylic acid solution was changed to a 0.1 mass % polyfunctional carboxylic acid solution, and the amount of polyfunctional carboxylic acid applied per area was 0.01 μg / mm 2 A laminate of Example 3 was produced in the same manner as in Example 1, except for the above change.

[0089] Example 4 The laminate of Example 4 was manufactured in the same manner as in Example 1, except that the silicon substrate having a metal layer in Example 1 was changed to a silicon substrate not having a metal layer (product name: Silicon Dicing Wafer, manufactured by GROWTH Corporation).

[0090] (Comparative Example 1) The laminate of Comparative Example 1 was produced in the same manner as in Example 1, except that in Example 1, a polyfunctional carboxylic acid layer was not formed between the silicon substrate and the low-melting-point metal layer, and the low-melting-point metal layer was placed directly on the silicon substrate.

[0091] (Comparative Example 2) In Example 1, the 0.2 mass % polyfunctional carboxylic acid solution was changed to a 10 mass % polyfunctional carboxylic acid solution, and the amount of polyfunctional carboxylic acid applied per area was 1 μg / mm 2 A laminate of Comparative Example 2 was produced in the same manner as in Example 1, except for the above change.

[0092] (Comparative Example 3) In Example 1, the 0.2% by mass polyfunctional carboxylic acid solution was changed to a 0.01% by mass polyfunctional carboxylic acid solution, and the amount of polyfunctional carboxylic acid applied per area was 0.001 μg / mm 2 A laminate of Comparative Example 3 was produced in the same manner as in Example 1, except for the above change.

[0093] Comparative Example 4 A laminate of Comparative Example 4 was produced in the same manner as in Example 1, except that glutaric acid, a dicarboxylic acid, was used and the 0.2 mass % polyfunctional carboxylic acid solution was changed to a 0.2 mass % glutaric acid solution.

[0094] (Comparative Example 5) A laminate of Comparative Example 5 was produced in the same manner as in Example 1, except that palmitic acid, a monocarboxylic acid, was used and the 0.2 mass% polyfunctional carboxylic acid solution was changed to a mixed solution of 0.2 mass% palmitic acid and 0.02 mass% diethanolamine.

[0095] Next, the "thermal conductivity" and "adhesion" of each of the obtained laminates were evaluated in the same manner as in Example 1. The results are shown in Tables 2 to 4 together with the results of Example 1.

[0096] [Table 1]

[0097] [Table 2]

[0098] [Table 3]

[0099] [Table 4]

[0100] The results in Tables 1 to 4 show that the laminate of Example 1 has superior adhesion to both the silicon substrate and the copper plate, which is the opposing substrate, compared to the laminate of Comparative Example 1, which does not have a multifunctional carboxylic acid layer. Furthermore, the thermal conductivity of indium is 81.8 [W / m K] according to literature, but the thermal conductivity of the indium sheet used in the examples when measured by the measurement method of this example was 53.9 [W / m K]. It was found that the laminate of Example 1 can produce a laminate having excellent thermal conductivity that compares favorably with the thermal conductivity of the indium sheet used as a reference example.

[0101] Furthermore, polyfunctional carboxylic acids (tricarboxylic acids) have superior wettability to dicarboxylic acids and monocarboxylic acids in all temperature ranges from room temperature to high temperatures (160°C). Compared to Comparative Example 4, which used a dicarboxylic acid, and Comparative Example 5, which used a monocarboxylic acid, Examples 1 to 4, which used polyfunctional carboxylic acids with three or more functionalities, had superior adhesion to both the silicon substrate and the copper plate, which was the opposing substrate, and it was found that a laminate with excellent thermal conductivity could be produced. [Industrial Applicability]

[0102] The laminate of the present invention can achieve excellent heat resistance, thermal conductivity, and adhesion as a thermal interface material (TIM), and is therefore suitable for use in, for example, the periphery of 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]

[0103] 1. Thermally 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, 50, 60 laminate 11 Low melting point metal layer 12, 12a, 12b Multifunctional carboxylic acid layer 13 Silicon substrate 14 Metal layer 15 Opposing substrate

Claims

1. a low-melting-point metal layer made of a low-melting-point metal; a polyfunctional carboxylic acid layer containing a trifunctional or higher polyfunctional carboxylic acid on the low-melting point metal layer, The content of the polyfunctional carboxylic acid per area of ​​the polyfunctional carboxylic acid layer is 0.002 μg / mm ２ 0.5 μg / mm or more ２ A laminate characterized by the following:

2. The laminate according to claim 1 , wherein the low-melting-point metal comprises at least one selected from the group consisting of Ga, Sn, Zn, Bi, and In.

3. 3. The laminate according to claim 1, wherein the polyfunctional carboxylic acid is represented by the following general formula (I): 【Chemical 1】 In the general formula (1), R １ ~R ３ each independently represents an alkylene group, a lactone skeleton, or a bond; R ４ represents a hydrogen atom or an alkyl group which may be substituted with a hydroxyl group, R ５ represents an alkylene group having 1 to 3 carbon atoms or an alkenyl group having 2 to 3 carbon atoms.

4. 3. The laminate according to claim 1, comprising the low-melting-point metal layer, the polyfunctional carboxylic acid layer, and either a silicon substrate or an opposing substrate on the polyfunctional carboxylic acid layer, in this order.

5. a first polyfunctional carboxylic acid layer on a first surface of the low-melting point metal layer, and a second polyfunctional carboxylic acid layer on a second surface of the low-melting point metal layer opposite to the first surface; The laminate according to claim 1 or 2, comprising, in this order, a silicon substrate, the first polyfunctional carboxylic acid layer, the low-melting point metal layer, the second polyfunctional carboxylic acid layer, and an opposing substrate.

6. The laminate according to claim 5 , wherein the opposing substrate contains at least one material selected from the group consisting of Cu, Ag, Au, and Pt.

7. The laminate according to claim 5 , wherein the silicon substrate has a metal layer on the side of the first polyfunctional carboxylic acid layer.

8. 6. The laminate according to claim 5, having a thermal conductivity of 30 W / (m·K) or more.

9. a step of applying a trifunctional or higher polyfunctional carboxylic acid onto a low-melting-point metal layer made of a low-melting-point metal, The amount of the polyfunctional carboxylic acid applied per area is 0.002 μg / mm ２ 0.5 μg / mm or more ２ A method for producing a laminate, characterized by:

10. The method for producing a laminate according to claim 9 , further comprising the step of placing one of a silicon substrate and an opposing substrate on the low-melting-point metal layer via the polyfunctional carboxylic acid, and heating the substrate to melt and solidify the low-melting-point metal.

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