Thermally conductive compositions and methods for manufacturing the same, and thermally conductive sheets

Abstract

Provide an ester compound represented by at least one of the following general formulas (1) and (2). In the above general formula (1), R1~R3 ​​represent hydrogen atoms, alkyl groups, or caprolactone skeletons. R4 represents hydrogen atoms or alkyl groups that can be replaced by hydroxyl groups. R5 represents divalent saturated hydrocarbon groups with 1~3 carbon atoms or divalent unsaturated hydrocarbon groups with 2~3 carbon atoms. In the above general formula (2), R1 and R2 represent hydrogen atoms, alkyl groups, or caprolactone skeletons. R4 and R6 represent hydrogen atoms or alkyl groups that can be replaced by hydroxyl groups. R5 represents a divalent saturated hydrocarbon group with 1 to 3 carbon atoms or a divalent unsaturated hydrocarbon group with 2 to 3 carbon atoms.

Description

[Technical Field]

[0001] This invention relates to ester compounds and methods for manufacturing ester compounds, as well as thermally conductive compositions and thermally conductive sheets. [Previous Technology]

[0002] In various electronic devices, such as LSIs, there are concerns that prolonged exposure to high temperatures due to the heat generated by the components used could lead to malfunctions or failures. Therefore, thermally conductive materials are widely used to prevent the LSIs from overheating. These thermally conductive materials prevent the device from overheating by dissipating or conducting the heat generated by the components to heat-dissipating components that release it to the atmosphere or other external systems.

[0003] If metal or ceramic is used as such a thermally conductive material, problems such as difficulty in weight reduction, poor processability, or reduced flexibility exist. Therefore, various solutions for thermally conductive materials using polymer materials formed from resins or rubbers as the base material have been proposed. For example, a thermosetting adhesive containing a curing component and a curing agent for the curing component, and a metal filler dispersed in the thermosetting adhesive, the metal filler having silver powder and solder powder, the solder powder exhibiting a melting temperature lower than the thermosetting treatment temperature of the thermally conductive adhesive, and reacting with the silver powder under the thermosetting treatment conditions of the thermosetting adhesive to generate a high-melting-point solder alloy exhibiting a melting point higher than the melting temperature of the solder powder, the curing agent being a curing agent with fluxing activity relative to the metal filler, and a thermally conductive adhesive having a curing component of glycidyl ether type epoxy resin and a curing agent of tricarboxylic acid monoanhydride has been proposed (for example, see Patent Document 1). Prior art documents Patent documents

[0004] Patent Document 1: Japanese Patent No. 5796242 [Summary of the Invention]

[0005] <The Problem the Invention Intends to Solve>

[0006] However, in the prior art described in Patent Document 1 above, there is a problem that the monoanhydride of tricarboxylic acid, which is a curing agent with fluxing activity, is decomposed by water or alcohol components contained in the thermosetting adhesive, resulting in a decrease in fluxing activity and curability. Furthermore, glutaric acid is known as a flux with a relatively small molecular weight, short hydrocarbon chain, and low melting point. However, if the aforementioned glutaric acid is incorporated into a thermally conductive adhesive, it precipitates as a solid crystal at room temperature, sometimes leading to poor coating performance. Moreover, glutaric acid has a melting point of 95°C to 98°C, which is relatively high, thus requiring high-temperature heating to achieve good wettability on metal surfaces. In addition, glutaric acid has a boiling point of around 200°C, raising concerns that not only does it volatilize and expand within the thermally conductive adhesive during high-temperature pressing, forming voids in the coating and significantly reducing thermal conductivity, but the remaining glutaric acid may also adversely affect the metal surrounding the semiconductor.

[0007] The objective of this invention is to solve the aforementioned problems and achieve the following: That is, the objective of this invention is to provide an ester compound and a method for manufacturing the ester compound that possess both excellent flux activity and curability, as well as a thermally conductive composition and a thermally conductive sheet. Methods for solving the problems

[0008] As a method for solving the above-mentioned problem, the following is provided. That is, <1> An ester compound, characterized in that it is represented by at least one of the following general formulas (1) and (2). [Chemical 1] In the above general formula (1), R1 to R3 represent a hydrogen atom, an alkyl group, or a caprolactone skeleton. R4 represents a hydrogen atom or an alkyl group that can be replaced by a hydroxyl group. R5 represents a divalent saturated hydrocarbon group having 1 to 3 carbon atoms or a divalent unsaturated hydrocarbon group having 2 to 3 carbon atoms. [Chemical 2] In the above general formula (2), R1 and R2 represent a hydrogen atom, an alkyl group, or a caprolactone skeleton. R4 and R6 represent a hydrogen atom or an alkyl group that can be replaced by a hydroxyl group. R5 represents a divalent saturated hydrocarbon group having 1 to 3 carbon atoms or a divalent unsaturated hydrocarbon group having 2 to 3 carbon atoms. <2> According to the ester compound described in <1> above, R5 is either an alkylene group having 2 to 3 carbon atoms or an vinylene group. <3> The ester compound according to <1> or <2> above is liquid at 25°C and 150°C. <4> The ester compound according to <1> or <2> above has a molecular weight of 800 g / mol or less. <5> The ester compound according to <1> or <2> above is a curing agent with fluxing activity. <6> A method for manufacturing an ester compound, characterized in that the method for manufacturing the ester compound according to <1> or <2> above includes the following step: a step of esterifying an anhydride with a polyfunctional alcohol. <7> In the method for manufacturing the ester compound according to <6> above, the anhydride is at least one selected from succinic anhydride, glutaric anhydride, and maleic anhydride. <8> In the method for manufacturing the ester compound according to <6> above, the polyfunctional alcohol is at least one of a caprolactone derivative and glycerol. <9> A thermally conductive composition, characterized in that it contains the ester compound described in <1> or <2> above, a curing component, thermally conductive particles, and low-melting-point metal particles. <10> According to the thermally conductive composition described in <9> above, the curing component is at least one of an epoxy resin and an oxobutane compound. <11> According to the thermally conductive composition described in <10> above, the epoxy resin is a glycidyl ether type epoxy resin. <12> According to the thermally conductive composition described in <9> above, the thermally conductive particles are at least one of copper particles, silver-coated particles, and silver particles. <13> According to the thermally conductive composition described in <9> above, the low-melting-point metal particles comprise Sn and at least one selected from Bi, Ag, Cu, and In. <14> A thermally conductive sheet, characterized in that it comprises a cured product of the thermally conductive composition described in <9> above. <Effects of the Invention>

[0009] According to the present invention, the above-mentioned problems can be solved and the above-mentioned objectives can be achieved. It is possible to provide ester compounds and ester compound manufacturing methods that have both excellent flux activity and curability, as well as thermally conductive compositions and thermally conductive sheets.

Implementation Method

[0011] (Ester Compounds) The ester compounds of the present invention are represented by at least one of the following general formulas (1) and (2).

[0012] [Chemical 3] In the above general formula (1), R1 to R3 represent hydrogen atoms, alkyl groups or caprolactone skeletons. R4 represents hydrogen atoms or alkyl groups that can be replaced by hydroxyl groups. R5 represents divalent saturated hydrocarbon groups with 1 to 3 carbon atoms or divalent unsaturated hydrocarbon groups with 2 to 3 carbon atoms.

[0013] [Chemical 4] In the above general formula (2), R1 and R2 represent hydrogen atoms, alkyl groups or caprolactone skeletons. R4 and R6 represent hydrogen atoms or alkyl groups that can be replaced by hydroxyl groups. R5 represents a divalent saturated hydrocarbon group with 1 to 3 carbon atoms or a divalent unsaturated hydrocarbon group with 2 to 3 carbon atoms.

[0014] In the above general formulas (1) and (2), the alkyl groups of R1 and R2 are preferably alkyl groups having 1 to 10 carbon atoms, and examples include methyl, ethyl, propyl, isopropyl, butyl, hexyl, heptyl, octyl, 2-ethylhexyl, tert-octyl, cyclohexyl, etc. The caprolactone skeleton in R1 and R2 is represented by the following general formula (i).

[0015] [Chemical 5] Wherein, in the above general formula (i), n represents an integer of 1 or more, preferably 1 to 10. m represents an integer of 2 or more, preferably 2 to 5.

[0016] As alkyl groups that can be substituted with hydroxyl groups in R4 and R6, examples include methyl, ethyl, propyl, -(CH2)-OH, -(CH2)2-OH, -(CH2)3-OH, etc.

[0017] R5 represents a divalent saturated hydrocarbon group having 1 to 3 carbon atoms or a divalent unsaturated hydrocarbon group having 2 to 3 carbon atoms. Examples of divalent saturated hydrocarbon groups having 1 to 3 carbon atoms in R5 include, for example, alkylene groups having 1 to 3 carbon atoms. Examples of alkylene groups having 1 to 3 carbon atoms include, for example, methylene (-CH 2-), ethylene (-CH 2CH 2-), propylene (-CH 2CH 2CH 2-), etc. Examples of divalent unsaturated hydrocarbon groups having 2 to 3 carbon atoms in R5 include, for example, vinylene (-CH=CH-), -CH=CH-CH 2-, etc. Among these, from the perspective of having both excellent flux activity and curability, either alkylene groups having 2 to 3 carbon atoms or vinylene groups are preferred.

[0018] The ester compounds represented by at least one of the above general formulas (1) and (2) can be synthesized by acting a specific polyfunctional alcohol on a specific acid anhydride, as described below.

[0019] (Method for manufacturing ester compounds) The method for manufacturing ester compounds of the present invention is a method for manufacturing ester compounds of the present invention, which includes a step of esterifying an acid anhydride with a polyfunctional alcohol, and further includes other steps as needed. There are no particular limitations on the esterification reaction of the acid anhydride with the polyfunctional alcohol, and it can be appropriately selected according to the purpose.

[0020] Examples of the aforementioned acid anhydrides include succinic anhydride, glutaric anhydride, maleic anhydride, phthalic anhydride, benzoic anhydride, and oxalic anhydride. One of these may be used alone, or two or more may be used in combination. Among these, succinic anhydride, glutaric anhydride, and maleic anhydride are preferred.

[0021] The aforementioned polyfunctional alcohol is preferably difunctional or more, more preferably difunctional or more functional but less than quadrifunctional. Examples of such polyfunctional alcohols include caprolactone derivatives, glycerol, ethylene glycol, and propylene glycol. One of these may be used alone, or two or more may be used in combination. Among these, caprolactone derivatives and glycerol are preferred.

[0022] Examples of the above-mentioned caprolactone derivatives include compounds having a caprolactone skeleton as shown in the above general formula (i). Commercially available products can be used as the above-mentioned caprolactone derivatives, and examples of such commercially available products include, for example, Plaxel 205, Plaxel 205U, Plaxel 303, and Plaxel 410 (all manufactured by Daicel Co., Ltd.).

[0023] The following shows an example of a specific esterification reaction of an anhydride with a 3-functional alcohol.

[0024] [Chemical 6] In the above reaction formula, R1 to R3 represent hydrogen atoms, alkyl groups, or caprolactone skeletons. R4 represents hydrogen atoms or alkyl groups that can be replaced by hydroxyl groups. R5 represents divalent saturated hydrocarbon groups with 1 to 3 carbon atoms or divalent unsaturated hydrocarbon groups with 2 to 3 carbon atoms.

[0025] <Other Processes> There are no special restrictions on other processes. They can be appropriately selected according to the purpose. Examples include concentration processes, separation and refining processes, etc.

[0026] The ester compound represented by at least one of the above general formulas (1) and (2) can simultaneously function as a good flux and a good curing agent. That is, the ester compound represented by at least one of the above general formulas (1) and (2) has the function of being liquid up to room temperature to high temperature, not reacting during film formation, improving the wettability of the coating liquid, and being heated in stages when used as an article, with the flux effect exerted by the first stage of heating, and then the epoxy resin simultaneously starting to cure by the second stage of heating. The first stage of heating is preferably 120°C to 150°C. The second stage of heating is preferably 150°C to 190°C.

[0027] The above-mentioned ester compound is preferably in liquid form at 25°C and 150°C. Here, liquid form means having a flowability suitable for coating. The fact that the ester compound is in liquid form at 25°C and 150°C can be confirmed, for example, by visually observing its flowability at 25°C (room temperature) and by observing the presence or absence of absorption peaks up to 150°C using DSC. Considering that the above-mentioned ester compound is in liquid form, the molecular weight is preferably 800 g / mol or less, more preferably 400 g / mol or more and 700 g / mol or less. The molecular weight of the above-mentioned ester compound can be determined, for example, using a Shodex (registered trademark) GPC-101 (manufactured by Showa Denko Corporation).

[0028] The ester compound is preferably a curing agent with fluxing activity. Because the ester compound has fluxing activity, it can improve the wettability of molten low-melting-point metal particles relative to thermally conductive particles by heating in the first stage, and can act as a curing agent by heating in the second stage, thereby curing the epoxy resin.

[0029] (Thermal Conductive Composition) The thermally conductive composition of the present invention contains the ester compound of the present invention, a curing component, thermally conductive particles and low-melting-point metal particles, and may further contain other components as needed.

[0030] <Ester Compound> The content of the ester compound of the present invention is not particularly limited and can be appropriately selected according to the purpose. It is preferably 0.5% by mass or more and 50% by mass or less relative to the total amount of the thermally conductive composition.

[0031] <Curing Components> The curing components are preferably at least one of epoxy resin and oxobutane compound.

[0032] -Epoxy Resin- There are no particular limitations on the epoxy resins mentioned above; they can be appropriately selected according to the purpose. Examples include phenolic varnish-type epoxy resins, cresol phenolic varnish-type epoxy resins, bisphenol A type epoxy resins, triphenol type epoxy resins, tetraphenol type epoxy resins, phenol-phenylenediamine type epoxy resins, naphthol-phenylenediamine type epoxy resins, phenol-naphthol type epoxy resins, phenol-dicyclopentadiene type epoxy resins, alicyclic epoxy resins, and aliphatic epoxy resins. One type can be used alone, or two or more types can be used in combination. Among these, glycidyl ether type epoxy resins are preferred from the perspectives of reactivity and economy.

[0033] -Oxetane Compounds- The above-mentioned oxetane compounds are compounds having an oxetane group, and can be aliphatic, alicyclic, or aromatic compounds. The above-mentioned oxetane compounds can be monofunctional oxetane compounds having only one oxetane group, or polyfunctional oxetane compounds having two or more oxetane groups.

[0034] There are no particular limitations on the above-mentioned oxetane compounds, and they can be appropriately selected according to the purpose. For example, 3,7-bis(3-oxetane)-5-oxa-nonane, 1,4-bis[(3-ethyl-3-oxetane-butylmethoxy)methyl]benzene, 1,2-bis[(3-ethyl-3-oxetane-butylmethoxy)methyl]ethane, 1,3-bis[(3-ethyl-3-oxetane-butylmethoxy)methyl]propane, ethylene glycol bis(3-ethyl-3-oxetane-butylmethyl) ether, triethylene glycol bis(3-ethyl-3-oxetane-butylmethyl) ether, tetraethylene glycol bis(3-ethyl-3-oxetane-butylmethyl) ether, and 1,4-bis(3-ethyl-3-oxetane-butylmethoxy)butane are examples. Alkane, 1,6-bis(3-ethyl-3-oxetane)methoxy)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-ethyloxetane-3-yl)methoxy]methyl}oxetane, phenylenediamine dioxetane, 4,4′-bis[(3-ethyl-3-oxetane)methoxymethyl]diphenyl (OXBP), bis[(3-ethyl-3-oxetane)methyl]isophthalate (OXIPA), etc. They can be used individually or in combination of two or more. Among these, 4,4′-bis[(3-ethyl-3-oxetane)methoxymethyl]diphenyl (OXBP) and bis[(3-ethyl-3-oxetane)methyl]isophthalate (OXIPA) are preferred.

[0035] As the above-mentioned oxetane compound, commercially available products can be used. Examples of such commercially available products include, for example, the "Aron oxetane (registered trademark)" series sold by Toa Synthetic Co., Ltd., and the "ETERNACOLL (registered trademark)" series sold by Ube Industries, Ltd.

[0036] The content of the above-mentioned curing component is not particularly limited and can be appropriately selected according to the purpose. It is preferably 0.3% by mass or more and 60% by mass or less, more preferably 0.5% by mass or more and 30% by mass or less, relative to the total amount of the thermally conductive composition.

[0037] <Thermal Conductive Particles> The thermal conductive particles described above are preferably at least one of copper particles, silver-coated particles, and silver particles. Examples of silver-coated particles include, for example, silver-coated copper particles, silver-coated nickel particles, and silver-coated aluminum particles. The shape of the thermal conductive particles is not particularly limited and can be appropriately selected according to the purpose; examples include spherical, flat, granular, and needle-shaped particles. The volume average particle size of the thermal conductive particles is preferably 10 μm or more and 300 μm or less, more preferably 20 μm or more and 100 μm or less. If the volume average particle size of the thermal conductive particles is 10 μm or more and 300 μm or less, the volume ratio of thermal conductive particles to low-melting-point metal particles can be increased, and high thermal conductivity and low thermal resistance of the thermal conductive composition can be achieved. The volume average particle size can be measured, for example, by a laser diffraction and scattering particle size distribution measuring device (product name: Microtrac MT3300EXII).

[0038] <Low Melting Point Metal Particles> As the aforementioned low melting point metal particles, solder particles specified in JIS Z3282-1999 are suitable. Examples of such solder particles include, for example, Sn-Pb-based solder particles, Pb-Sn-Sb-based solder particles, Sn-Sb-based solder particles, Sn-Pb-Bi-based solder particles, Sn-Bi-Ag-based solder particles, Sn-Cu-based solder particles, Sn-Pb-Cu-based solder particles, Sn-In-based solder particles, Sn-Ag-based solder particles, Sn-Pb-Ag-based solder particles, Pb-Ag-based solder particles, and Sn-Ag-Cu-based solder particles. One type may be used alone, or two or more types may be used together. Among these, solder particles preferably contain Sn and at least one selected from Bi, Ag, Cu and In, and more preferably Sn-Bi-based solder particles, Sn-Bi-Ag-based solder particles, Sn-Ag-Cu-based solder particles, and Sn-In-based solder particles.

[0039] The shape of the aforementioned low-melting-point metal particles is not particularly limited and can be appropriately selected according to the purpose. Examples include spherical, flat, granular, and needle-shaped particles. The melting point of the aforementioned low-melting-point metal particles is preferably 100°C to 250°C, more preferably 120°C to 200°C. The melting point of the aforementioned low-melting-point metal particles is lower than the heat-curing temperature of the aforementioned thermally conductive composition. Considering that the low-melting-point metal particles melted in the cured product of the thermally conductive composition can form a network (a continuous phase of metal) using thermally conductive particles, it is preferable to achieve high thermal conductivity and low thermal resistance. The aforementioned low-melting-point metal particles react with the aforementioned thermally conductive particles under the heat-curing conditions of the aforementioned thermally conductive composition to form an alloy with a higher melting point than the aforementioned low-melting-point metal particles, thereby preventing melting at high temperatures and improving reliability. Furthermore, the heat resistance of the cured product of the thermally conductive composition is improved. The thermal curing treatment of the above-mentioned thermally conductive composition is, for example, carried out at a temperature of 150°C to 200°C for 30 minutes to 2 hours.

[0040] The volume average particle size of the aforementioned low-melting-point metal particles is preferably 10 μm or less, more preferably 1 μm or more and 5 μm or less. If 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 and low thermal resistance in the thermally conductive composition. The volume average particle size of the aforementioned low-melting-point metal particles can be measured in the same manner as the volume average particle size of the aforementioned thermally conductive particles.

[0041] <Other Components> The above-described thermally conductive composition may contain other components as long as it does not impair the effects of the present invention. There are no particular limitations on the other components mentioned above, and they can be appropriately selected according to the purpose. Examples include thermally conductive particles other than metals (e.g., aluminum nitride, alumina, carbon fiber, etc.), adhesive resins, additives (e.g., antioxidants, ultraviolet absorbers, curing accelerators, silane coupling agents, leveling agents, flame retardants, etc.).

[0042] -Adhesive Resin- There are no particular limitations on the adhesive resin, and it can be appropriately selected according to the purpose. Examples include polybutadiene, polysiloxane, poly(meth)acrylate, polyalkylene compounds, polyalkylene oxide compounds, polyisoprene, polyisobutylene, polyamide compounds, polycarbonate, etc. One of them can be used alone, or two or more can be used in combination.

[0043] The thermally conductive composition of the present invention can be prepared by uniformly mixing the ester compound, epoxy resin, thermally conductive particles, low-melting-point metal particles, and other components as needed by conventional methods.

[0044] The above-described thermally conductive composition can be either a sheet-like thermally conductive sheet or a paste-like thermally conductive paste (sometimes referred to as a thermally conductive adhesive or thermally conductive grease). Among these, a thermally conductive sheet is preferred from the perspective of ease of handling, while a thermally conductive paste is preferred from the perspective of cost.

[0045] (Thermal Conductive Sheet) The thermal conductive sheet of the present invention comprises a cured product of the thermal conductive composition of the present invention, and is formed by sheeting the thermal conductive composition of the present invention. From the viewpoint of thinning, the average thickness of the above-mentioned thermal conductive sheet is preferably 500 μm or less, more preferably 200 μm or less, and even more preferably 100 μm or less. The lower limit of the average thickness of the above-mentioned thermal conductive sheet is not particularly limited and can be appropriately selected according to the purpose; preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 50 μm or more.

[0046] There are no particular limitations on the manufacturing method of the above-mentioned thermally conductive sheet, and it can be appropriately selected according to the purpose. Examples include (1) a method of molding the above-mentioned thermally conductive composition into a predetermined shape and curing it to form a thermally conductive molded body, and cutting the obtained thermally conductive molded body into sheets to manufacture a thermally conductive sheet; and (2) a method of forming a cured layer containing the above-mentioned thermally conductive composition on a support with a release layer to manufacture a thermally conductive sheet. In addition, in the above (2), when the thermally conductive sheet is laminated on the heat-dissipating substrate, the support is peeled off.

[0047] The thermally conductive composition and thermally conductive sheet of the present invention, for example, are embedded in a small gap between a heat source such as an LSI and a heat sink, thereby making them suitable for use in a thermal interface material (TIM1) that allows heat to flow smoothly between the two. When an LED chip or a heat-dissipating substrate on which an IC chip is mounted is connected to a heat sink to form a power LED module or a power IC module, the following applies: Here, as a power LED module, there are lead-bonded mounting type modules and flip-chip mounting type modules; as a power IC module, there are lead-bonded mounting type modules.

[0048] <Heat-exothermic structure> The heat-exothermic structure used in this invention is composed of a heating element, a thermally conductive material, and a heat-exothermic component. Between the heating element and the heat-exothermic component, there is a cured product of the thermally conductive composition of this invention, which serves as the thermally conductive material.

[0049] As the aforementioned heat source, there are no particular limitations, and it can be appropriately selected according to the purpose. Examples include electronic components such as CPU (Central Processing Unit), MPU (Micro Processing Unit), and GPU (Graphics Processing Unit).

[0050] As the heat-dissipating component, if it is a structure that dissipates heat emitted by the heat-dissipating electronic component (heat-generating element), there are no particular limitations, and it can be appropriately selected according to the purpose. Examples include heat dissipation components, radiators, vapor chambers, heat pipes, etc. The heat dissipation component is a component used to efficiently conduct the heat of the electronic component to other components. As the material of the heat dissipation component, there are no particular limitations, and it can be appropriately selected according to the purpose. Examples include copper, aluminum, etc. The heat dissipation component is usually flat. The radiator is a component used to dissipate the heat of the electronic component into the air. As the material of the radiator, there are no particular limitations, and it can be appropriately selected according to the purpose. Examples include copper, aluminum, etc. The radiator, for example, has a plurality of fins. The radiator, for example, has a base and a plurality of fins that extend in a non-parallel direction (e.g., an orthogonal direction) relative to the side of the base. The heat dissipation component and the radiator are generally solid structures without internal space. The vapor chamber is a hollow structure. The internal space of the aforementioned hollow structure is sealed with a volatile liquid. Examples of such a vapor chamber include a vapor chamber in which the heat dissipation member is a hollow structure, or a plate-shaped hollow structure such as a hollow radiator. The aforementioned heat pipe is a cylindrical, substantially cylindrical, or flat cylindrical hollow structure. The internal space of the aforementioned hollow structure is sealed with a volatile liquid.

[0051] Here, FIG1 is a schematic cross-sectional view showing an example of a semiconductor device as a heat-dissipating structure. The cured product (thermal conductive sheet) 1 of the thermally conductive composition of the present invention dissipates the heat emitted by the electronic component 3 such as the semiconductor element. As shown in FIG1, it is fixed to the main surface 2a opposite to the heat dissipation member 2 and the electronic component 3, and is held between the electronic component 3 and the heat dissipation member 2. Furthermore, the thermally conductive sheet 1 is held between the heat dissipation member 2 and the heat sink 5. Moreover, the thermally conductive sheet 1 and the heat dissipation member 2 together constitute a heat-dissipating member that dissipates the heat of the electronic component 3.

[0052] The heat dissipation member 2 is formed, for example, in the shape of a square plate, having a main surface 2a facing the electronic component 3, and a side wall 2b erected along the outer periphery of the main surface 2a. A thermally conductive sheet 1 is provided on the main surface 2a surrounded by the side wall 2b of the heat dissipation member 2, and a heat sink 5 is provided on the other side 2c opposite to the main surface 2a, separated by the thermally conductive sheet 1. The higher the thermal conductivity of the heat dissipation member 2, the lower the thermal resistance, and the more efficiently it absorbs the heat from the electronic component 3, such as the semiconductor element. Therefore, for example, it can be formed using copper or aluminum, which have good thermal conductivity.

[0053] The electronic component 3, for example, is a semiconductor element such as a BGA, and is mounted on the wiring substrate 6. Furthermore, in the heat dissipation member 2, the front end face of the sidewall 2b is mounted on the wiring substrate 6, thereby surrounding the electronic component 3 at predetermined intervals via the sidewall 2b. Moreover, the main surface 2a of the heat dissipation member 2 is connected to a thermally conductive sheet 1, thereby absorbing the heat emitted by the electronic component 3, forming a heat dissipation member from which heat is released by the heat sink 5. Example

[0054] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited by these embodiments.

[0055] (Example 1) <Synthesis of Ester Compound> In a three-necked glass flask equipped with a thermocouple, a stirrer, a cooling tube, and a heating device, 50 parts by mass of caprolactone derivative (manufactured by Daicel Co., Ltd., Plaxel 303) as shown in the following general formula (ii) were measured, and 43.3 parts by mass of methyl ethyl ketone (manufactured by Fujifilm and Kohden Chemical Co., Ltd.) were added, and the mixture was stirred thoroughly to dissolve it completely. Next, as a catalyst, 1 part by mass of triethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) was added, and the mixture was stirred thoroughly again. After it was completely dissolved, 50 parts by mass of glutaric anhydride (manufactured by Tokyo Chemical Industry Co., Ltd.) represented by the following structural formula was added dropwise in powder form to the three-necked flask using a funnel. The reaction was maintained at 60°C and stirred for 24 hours until the above reaction was completely completed. After cooling the above synthesized compound to room temperature, it was transferred to a gaiwan flask, concentrated using an evaporator, and then dried under reduced pressure (at 60°C for 24 hours) to obtain the desired ester compound in 93% yield.

[0056] [General Formula (ii)]<Caprolactone derivative (manufactured by Daicel Co., Ltd., Plaxel 303)> [Chemical 7] However, R represents a hydrogen atom or an alkyl group. n represents an integer greater than 1.

[0057] [Chemical 8]

[0058] (Example 2) <Synthesis of Ester Compound> In Example 1, glutaric anhydride (manufactured by Tokyo Chemical Industry Co., Ltd.) was replaced with succinic anhydride (manufactured by Fujifilm and Wako Pure Chemical Industries Co., Ltd.) represented by the following structural formula. Otherwise, the synthesis of the ester compound was carried out in the same manner as in Example 1. The desired compound was in liquid form with a yield of 95%.

[0059] [Chemical 9]

[0060] (Example 3) <Synthesis of Ester Compound> In Example 1, glutaric anhydride (manufactured by Tokyo Chemical Industry Co., Ltd.) was replaced with maleic anhydride (manufactured by Fujifilm and Wako Pure Chemical Industries Co., Ltd.) represented by the following structural formula. Otherwise, the synthesis was carried out in the same manner as in Example 1. The desired ester compound was in liquid form with a yield of 91%.

[0061] [Chemical 10]

[0062] (Example 4) <Synthesis of Ester Compound> In Example 1, the caprolactone derivative (Daicel Co., Ltd., Plaxel 303) was replaced with glycerol (Fujifilm and Kohden Chemical Co., Ltd.), and the synthesis was carried out in the same manner as in Example 1. The target compound was in liquid form with a yield of 90%.

[0063] (Example 5) <Synthesis of Ester Compound> In Example 1, the caprolactone derivative (manufactured by Daicel Co., Ltd., Plaxel 303) was replaced with the caprolactone derivative shown in general formula (iii) below (manufactured by Daicel Co., Ltd., Plaxel 205U), and the synthesis was carried out in the same manner as in Example 1. The desired compound was in liquid form with a yield of 90%.

[0064] [General Formula (iii)]<Caprolactone Derivative (Daicel Co., Ltd., Plaxel 205U)> [Chemical 11] Wherein, R represents a hydrogen atom or an alkylene group. n represents an integer of 1 or more, and m represents an integer of 1 or more.

[0065] (Example 6) In Example 2, the caprolactone derivative (manufactured by Daicel Co., Ltd., Plaxel 303) was replaced with the caprolactone derivative shown in general formula (iii) above (manufactured by Daicel Co., Ltd., Plaxel 205U). Otherwise, the synthesis was carried out in the same manner as in Example 2. The target compound was in liquid form with a yield of 90%.

[0066] (Comparative Example 1) <Synthesis of Ester Compound> In Example 1, glutaric anhydride (manufactured by Tokyo Chemical Industry Co., Ltd.) was replaced with "MH-700" (ricassid MH-700, manufactured by Shin Nippon Rika Co., Ltd.), represented by the following structural formula. Otherwise, the synthesis was carried out in the same manner as in Example 1. The desired compound was in solid form with a yield of 94%.

[0067] [Chemical 12]

[0068] (Comparative Example 2) <Synthesis of Ester Compound> In Example 1, glutaric anhydride (manufactured by Tokyo Chemical Industry Co., Ltd.) was replaced with "H-TMAn-S" (manufactured by Mitsubishi Chemical Co., Ltd.), represented by the following structural formula. Otherwise, the synthesis was carried out in the same manner as in Example 1. The desired compound was in solid form with a yield of 88%.

[0069] [Chemical 13]

[0070] (Comparative Example 3) Prepare unesterified glutaric acid (manufactured by Tokyo Chemical Industry Co., Ltd.).

[0071] Next, the properties and molecular weights of the ester compounds of Examples 1-6, Comparative Examples 1-2, and Comparative Example 3 were determined as follows. The results are shown in Tables 1-1 and 1-2.

[0072] <Confirmation of the properties of the ester compound and glutaric acid> The ester compound and glutaric acid are liquid at 25°C and 150°C. The presence or absence of fluidity is confirmed visually at 25°C. Differential scanning calorimetry (DSC) is then used to confirm the presence or absence of an endothermic peak up to 150°C. • Solid at 25°C, with an endothermic peak up to 150°C → Liquid at 150°C • Solid at 25°C, with no endothermic peak up to 150°C → Solid at 150°C

[0073] <Molecular weight of ester compounds> The molecular weight of ester compounds was determined using Shodex (registered trademark) GPC-101 (manufactured by Showa Denko Corporation).

[0074] [Table 1-1]

[0075] [Table 1-2]

[0076] (Examples 7-18 and Comparative Examples 4-9) <Preparation of Thermally Conductive Compositions> The compositions and contents shown in Tables 2-1 to 2-3 were mixed in a homogeneous manner using a stirring device (Foam Remover Mixer, Automatic Rotation Mixer, Thinky Co., Ltd.) to prepare the thermally conductive compositions of Examples 7-18 and Comparative Examples 4-9.

[0077] <Preparation of Cured Products> After coating each thermally conductive composition on an aluminum substrate (A5052P) of 30mm×30mm×2mm, a spacer with a height of 0.125mm is placed, and another aluminum substrate (30mm×30mm×2mm) is placed on the spacer. The thermally conductive compositions are sandwiched between the two aluminum substrates so that each thermally conductive composition has a thickness of 0.125mm and a side thickness of 20mm. The mixture is then cured in an oven at 150°C for 60 minutes to obtain a cured product (interface Al) of each thermally conductive composition.

[0078] <Curing Properties> Next, the curing properties of each cured product were evaluated based on the following criteria. The results are shown in Tables 2-1 to 2-3. [Evaluation Criteria] 〇: Cannot peel two aluminum substrates △: Can peel two aluminum substrates using pliers, etc. ×: Can easily peel two aluminum substrates by hand

[0079] Next, the following procedures were performed to measure the thermal conductivity. The results are shown in Tables 2-1 to 2-3. <Thermal Conductivity> After coating each thermally conductive composition onto a copper substrate (30mm × 30mm × 2mm), a spacer with a height of 0.125mm was placed, and another copper substrate (30mm × 30mm × 2mm) was placed on the spacer. The thermally conductive compositions were sandwiched between the two copper substrates such that each composition had a thickness of 0.125mm and a side thickness of 20mm. The substrates were then oven-cured at 150°C for 60 minutes. The thermal resistance (°C·cm² / W) of the cured product (interface Cu) of each thermally conductive composition was measured using a method based on ASTM-D5470. The thermal resistance of the cured product was calculated by subtracting the thermal resistance of the copper substrate from the result. The thermal conductivity (W / mK) was then determined from the thermal resistance and the thickness of the cured product and evaluated according to the following criteria. [Evaluation Criteria] 〇: Thermal conductivity ≥ 11.0 W / m·K △: Thermal conductivity ≥ 8.0 W / m·K and < 11.0 W / m·K ×: Thermal conductivity < 8.0 W / m·K

[0080] [Table 2-1]

[0081] [Table 2-2]

[0082] [Table 2-3]

[0083] Detailed information on each material in Tables 2-1 to 2-3 is as follows: • Base polymer: M1276, manufactured by Arkema Corporation, a polyamide compound. • Epoxy resin: Glycidyl ether type epoxy resin, AER9000, manufactured by Asahi Kasei Corporation (epoxy equivalent: 350). • Oxycyclobutane compound: 4,4′-bis[(3-ethyl-3-oxetane)methoxymethyl]diphenyl (OXBP), manufactured by UBE Corporation. • Thermally conductive particles: Ag-coated Cu particles, manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., volume average particle size Dv: 40 μm. • Low melting point metal particles: Sn 58Bi 42, manufactured by Mitsui Metal Mining Co., Ltd., volume average particle size Dv: 4 μm, melting point 139°C. Industrial availability.

[0084] The thermally conductive composition and thermally conductive sheet of the present invention can achieve high thermal conductivity and low thermal resistance. For example, they are suitable for use around various electrical devices such as CPUs, MPUs, power transistors, LEDs, laser diodes, and various batteries (such as lithium-ion batteries, various fuel cells, capacitors, amorphous silicon, crystalline silicon, compound semiconductors, wet solar cells, and various solar cells) where temperature has an adverse effect on the efficiency and lifespan of component operation; around heat sources of heating equipment that require efficient heat utilization; and around heat pipes of heat exchangers and floor heating devices.

[0085] This international application claims priority based on Japanese Patent Application No. 2022-045665, filed on March 22, 2022, and Japanese Patent Application No. 2022-205410, filed on December 22, 2022, and incorporates the entire contents of Japanese Patent Application No. 2022-045665 and Japanese Patent Application No. 2022-205410 into this international application. [Simplified Explanation of the Diagram]

[0010] Figure 1 is a schematic cross-sectional view showing an example of the heat-dissipating structure used in the present invention.

Claims

1. A thermally conductive composition, characterized in that it comprises: an ester compound which is liquid at 25°C and 150°C and is represented by at least one of the following general formulas (1) and (2), and a curing component, thermally conductive particles, and low-melting-point metal particles; [Chemical 1] wherein, In the general formula (1), R1 to R3 represent hydrogen atoms, alkyl or caprolactone skeletons, R4 represents hydrogen atoms or alkyl groups that can be replaced by hydroxyl groups, and R5 represents divalent saturated hydrocarbon groups with 1 to 3 carbon atoms or divalent unsaturated hydrocarbon groups with 2 to 3 carbon atoms. [Chemical 2] In the general formula (2), R1 and R2 represent hydrogen atoms, alkyl or caprolactone skeletons, R4 and R6 represent hydrogen atoms or alkyl groups that can be replaced by hydroxyl groups, and R5 represents divalent saturated hydrocarbon groups with 1 to 3 carbon atoms or divalent unsaturated hydrocarbon groups with 2 to 3 carbon atoms.

2. The thermally conductive composition according to claim 1, wherein R5 is either an alkylene group having 2 to 3 carbon atoms or an vinylene group.

3. The thermally conductive composition according to claim 1 or 2, wherein the ester compound has a molecular weight of 800 g / mol or less.

4. The thermally conductive composition according to claim 1 or 2, wherein the curing agent is a fluxing agent.

5. A method for manufacturing a thermally conductive composition, characterized in that the method for manufacturing the thermally conductive composition according to claim 1 or 2 includes the following step: an esterification reaction of an acid anhydride with a polyfunctional alcohol.

6. The method for manufacturing the thermally conductive composition according to claim 5, wherein the anhydride is selected from at least one of succinic anhydride, glutaric anhydride, and maleic anhydride.

7. The method for manufacturing the thermally conductive composition according to claim 5, wherein the polyfunctional alcohol is at least one of a caprolactone derivative and glycerol.

8. The thermally conductive composition according to claim 1, wherein the curing component is at least one of an epoxy resin and an oxetine compound.

9. The thermally conductive composition according to claim 8, wherein the epoxy resin is a glycidyl ether type epoxy resin.

10. The thermally conductive composition according to claim 1, wherein the thermally conductive particles are at least any one of copper particles, silver-coated particles, and silver particles.

11. The thermally conductive composition according to claim 1, wherein the low-melting-point metal particles comprise Sn and at least one selected from Bi, Ag, Cu and In.

12. A thermally conductive sheet, characterized in that it comprises a cured product of the thermally conductive composition described in claim 1.

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