Method for manufacturing a thermally conductive structure and a method for manufacturing a heat dissipation structure

Abstract

To provide a method for manufacturing a thermally conductive structure that can achieve both formation of a desired film thickness and flattening.SOLUTION: A method for manufacturing a thermally conductive structure includes: a resin frame formation step of applying a resin composition containing resin and foaming agent to an adherend 11 to form a resin frame 12; a liquid film formation step of applying a thermally conductive composition 13a containing a thermally conductive material to the inside of the resin frame 12 by an ink jet method to form a liquid film 13b; a heating step of heating the liquid film 13b and the resin frame 12 to solidify the liquid film 13b and foam the resin frame 12; a removal step of removing the resin frame 12 foamed by heating from the adherend 11; and a curing step of, after removing the resin frame 12, heating to cure the solidified liquid film 13b.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a heat-conductive structure and a method for manufacturing a heat-dissipating structure.

Background Art

[0002] In recent years, in electronic circuit boards, with the increase in integration density and speed, the degradation of circuit performance due to heat-generating bodies such as IC chips has become a problem, and higher performance of heat-dissipating technologies for suppressing temperature rise has been demanded. As such a heat-dissipating technology, a method of providing a heat-dissipating member such as a heat sink to a heat-generating body such as an IC chip has been adopted. For example, in order to enhance the thermal conductivity in the thermal interface material (TIM: Thermal interface material) of the heat-dissipating structure shown in FIG. 1, as the heat-conductive structure (heat-conductive sheet) 1 disposed between the heat-generating body 3 and the heat-dissipating member 5, for example, an alkaline resin heat-dissipating foam sheet obtained by mixing bubbles into an acrylic resin containing a heat-conductive substance to form a foam has been proposed (see, for example, Patent Document 1).

[0003] On the other hand, the inkjet method is a technique that can apply a desired material to a desired site on demand, and in recent years, its use in fields other than image formation has been expected. In the inkjet method, since the viscosity of the liquid composition to be applied is low, on a flat adherend, it is easy for the droplets to spread and level after landing, so it is advantageous when performing planarization of the coating film and highly accurate film thickness control.

[0004] However, in the inkjet method, in order to ensure ejection stability, it is necessary to lower the solid content concentration of the heat-conductive composition, and it is difficult to form a film aiming for a film thickness of 10 μm or more. Further, when forming a film of a heat-conductive composition for the purpose of heat dissipation on the surface of an IC package, the film thickness is preferably 10 μm to 100 μm when (1) there are irregularities of several μm on the surface of the IC package, or (2) when relaxing the thermal stress at the coating film interface. If the film thickness is too thick, it becomes difficult to make the device thinner, and if the film thickness is too thin, it becomes difficult to fill the irregularities on the surface of the IC package and relax the thermal stress.

[0005] Therefore, in order to solve the above problems, a technique has been proposed in which the coated portion of the substrate to which the liquid composition is applied is heated with an air heater to increase the film thickness (see, for example, Patent Document 2). However, excessive heating of the liquid composition immediately after coating, as proposed in this case, is one of the causes of impairing the flattening of the coating film by leveling and the high-precision film thickness control, which are characteristics of the inkjet method.

[0006] Furthermore, as described in Patent Document 1 above, when manufacturing TIM using a thermally conductive composition containing metal particles by an inkjet method, the thermally conductive composition containing metal particles is generally expensive. Using a resin to increase the thickness is preferable not only from a cost perspective, but also from the standpoint of improving mechanical strength by using a highly adhesive resin. However, with the inkjet method, it is difficult to obtain the desired film thickness because the droplets spread out. Therefore, when manufacturing TIMs using the inkjet method, it was extremely difficult to achieve both the desired film thickness and planarization simultaneously. [Overview of the project] [Problems that the invention aims to solve]

[0007] The present invention aims to provide a method for manufacturing a thermally conductive structure that can achieve both the desired film thickness and planarization. [Means for solving the problem]

[0008] The present invention provides a method for manufacturing a thermally conductive structure as a means for solving the aforementioned problems, comprising: a resin frame forming step of applying a resin composition containing a resin and a foaming agent to form a resin frame; a liquid film forming step of applying a thermally conductive composition containing a thermally conductive substance to the inside of the resin frame by an inkjet method to form a liquid film; a heating step of heating the liquid film and the resin frame to solidify the liquid film and foam the resin frame; and a removal step of removing the resin frame. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a method for manufacturing a thermally conductive structure that can achieve both the desired film thickness and planarization. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic cross-sectional view showing an example of a heat dissipation structure. [Figure 2] Figure 2 shows an example of the orientation state of carbon fibers as a thermally conductive material. [Figure 3] Figure 3 is a process diagram showing an example of a method for manufacturing a thermally conductive structure according to the first embodiment. [Figure 4] Figure 4 is a process diagram showing an example of a method for manufacturing a thermally conductive structure according to the second embodiment. [Modes for carrying out the invention]

[0011] (Method for manufacturing a thermally conductive structure) The method for manufacturing the thermally conductive structure of the present invention includes a resin frame forming step, a liquid film forming step, a heating step, and a removal step, preferably including a curing step, and further including other steps as necessary.

[0012] In the present invention, the process includes a resin frame forming step of applying a resin composition containing a resin and a foaming agent to form a resin frame, a liquid film forming step of applying a thermal conductive composition containing a thermal conductive substance to the inside of the resin frame by an inkjet method to form a liquid film, a heating step of heating the liquid film and the resin frame to solidify the liquid film and foam the resin frame, and a removal step of removing the resin frame. As a result, the resin frame prevents the liquid thermal conductive composition from wetting and spreading, and the liquid film solidifies and the resin frame foams up upon heating, allowing for easy removal. Therefore, a flat thermal conductive structure with a desired film thickness can be efficiently manufactured.

[0013] <Resin frame formation process> The resin frame forming process involves applying a resin composition containing a resin and a foaming agent to form a resin frame. The aforementioned resin composition contains a resin and a foaming agent, preferably a solvent, and may further contain other components as needed.

[0014] -Foaming agent- There are no particular restrictions on the foaming agent, and it can be appropriately selected depending on the purpose. Examples include ammonium carbonate (foaming temperature: 58°C), 2,2'-azobisisobutyronitrile (foaming temperature: 85°C to 90°C), azohexahydrobenzonitrile (foaming temperature: 103°C to 104°C), diazoaminobenzene (foaming temperature: 90°C to 100°C), benzenesulfohydrazide (foaming temperature: 90°C to 100°C), p-toluenesulfonylhydrazide (foaming temperature: 110°C), diphenylsulfone-3,3'-disulfohydrazide (foaming temperature: 148°C), diphenyloxide-4,4'-disulfohydrazide (foaming temperature: 150°C), N,N'-dinitroso-N,N'-dimethylterephthalamide (foaming temperature: 105°C), and terephthalazide (foaming temperature: 90°C to 110°C). These can be used individually or in combination of two or more. Note that the foaming temperature is synonymous with the decomposition temperature. The foaming agent preferably has a foaming temperature (decomposition temperature) of 200°C or less, more preferably 150°C or less, and even more preferably 50°C to 130°C. If a foaming agent has a foaming temperature exceeding 200°C, heating it to a temperature above 200°C to foam it will cause the thermally conductive composition to fully harden, making it impossible to bond the heat dissipation component in subsequent processes. This necessitates the use of a conductive adhesive when bonding the heat dissipation component.

[0015] -resin- The aforementioned resin is not particularly limited and can be appropriately selected depending on the purpose. Examples include polypropylene resin, silicone resin, fluororesin, polyacetal resin, ethylene propylene diene rubber (EPDM), polyvinyl chloride resin, polyamide resin, polyethylene resin, polycarbonate resin, polyester resin, and polystyrene resin. These may be used individually or in combination of two or more.

[0016] - Solvent - There is no particular limitation on the solvent, and it can be appropriately selected according to the purpose. For example, xylene, toluene, butyl acetate, N-methyl-2-pyrrolidone, 2-pyrrolidone, cyclohexanone, methyl isobutyl ketone, methyl ethyl ketone, N,N-dimethylacetamide, 2-n-butoxymethanol, 2-dimethylethanol, etc. can be mentioned. These may be used alone or in combination of two or more. Among these solvents, those with a boiling point of 80°C to 150°C are preferred. If the boiling point of the solvent is too high, the resin composition is likely to spread and wet, and in the case of non-plate printing such as the inkjet method and the dispenser method,fine patterning may be difficult. On the other hand, if the boiling point of the solvent is too low, the resin composition may dry too quickly, making it difficult to have a stable process.

[0017] - Other components - There is no particular limitation on the other components, and they can be appropriately selected according to the purpose. For example, thixotropy imparting agents, dispersants, curing accelerators, retarders, micro-adhesion imparting agents, plasticizers, flame retardants, antioxidants, stabilizers, colorants, etc. can be mentioned.

[0018] By applying the resin composition onto the adherend and drying it, a resin frame can be formed on the adherend. There is no particular limitation on the method of applying the resin composition, and it can be appropriately selected according to the purpose. For example, inkjet method, dispenser method, screen printing method, dip coating method, spray coating method, spin coating method, bar coating method, slot die coating method, doctor blade coating method, curtain coating method, offset printing method, gravure printing method, flexographic printing method, letterpress printing method, screen printing method, electrophotographic printing method by liquid development method, etc. can be mentioned. Among these, the inkjet method and the dispenser method are preferred because patterning is easy, and the inkjet method is more preferred because it is possible to control the position where the droplets are ejected.

[0019] -Substrate- The substrate has no particular restrictions on its material, shape, size, structure, etc., and can be appropriately selected according to the purpose. The material of the substrate has no particular restrictions and can be appropriately selected according to the purpose. For example, metals, resins, ceramics, glass, etc. can be mentioned. Among these, metals are preferred. Examples of the metal include copper, aluminum, silver, or alloys thereof. The material of the substrate has no particular restrictions and can be appropriately selected according to the purpose. For example, flat plate shape, sheet shape, film shape, etc. can be mentioned. The structure of the substrate has no particular restrictions and can be appropriately selected according to the purpose. For example, it may be a single-layer structure or a multi-layer structure. Specific examples of the substrate include electronic components, heat dissipation members, etc. The electronic components have no particular restrictions and can be appropriately selected according to the purpose. For example, CPU (Central Processing Unit), MPU (Micro Processing Unit), GPU (Graphics Processing Unit), etc. can be mentioned.

[0020] When the area of the resin frame is larger than the area of the substrate, the adhesion area between the substrate and the heat dissipation member will become smaller. Therefore, it is preferable to finely pattern the resin composition. For this reason, it is preferable to heat the substrate to such an extent that the foaming agent in the resin frame does not foam, and promptly evaporate the solvent from the resin composition.

[0021] The height of the resin frame is preferably equal to or greater than the wet film thickness of the heat-conductive composition (liquid) corresponding to the film thickness of the heat-conductive composition (film) to be formed. When the aforementioned heat-conductive composition (liquid) is applied, for example, if the solid content concentration of the heat-conductive composition (liquid) is 10% by volume and the target film thickness is 20 μm, then using wet film thickness (μm) × 0.1 ≈ 20 μm as a guideline, the wet film thickness of the liquid will be 200 μm. Therefore, it is preferable that the height of the resin frame be 200 μm or more.

[0022] <Liquid film formation process> The liquid film formation step involves applying a thermally conductive composition containing a thermally conductive substance to the inside of the resin frame using an inkjet method to form a liquid film.

[0023] The aforementioned thermally conductive composition preferably contains a thermally conductive substance, a resin, and a solvent, and may further contain other components as needed.

[0024] -Thermal conductive materials- The thermally conductive material is preferably in particulate form, and more preferably in the form of flake-shaped (small pieces shaped like fish scales), plate-shaped (disc-shaped, hexagonal plate-shaped, etc.), cylindrical, prismatic, or elliptical particles. Examples of the thermally conductive material include metal particles such as copper, aluminum, iron, silver, zinc, and indium; aluminum oxide particles, magnesium oxide particles, boron nitride particles, talc particles, aluminum nitride particles, aluminum hydroxide particles, graphite, graphene, and carbon fibers. These may be used individually or in combination of two or more. Among these, metal particles such as silver and copper, and carbon fibers are preferred due to their high thermal conductivity.

[0025] There are no particular restrictions on the carbon fibers, and they can be appropriately selected depending on the purpose. Examples include pitch-based carbon fibers, PAN-based carbon fibers, graphitized PBO fibers, and carbon fibers synthesized by methods such as arc discharge, laser evaporation, CVD (chemical vapor deposition), and CCVD (catalytic chemical vapor deposition). These may be used individually or in combination of two or more types. Among these, graphitized PBO fibers, PAN-based carbon fibers, and pitch-based carbon fibers are preferred from the viewpoint of thermal conductivity, with pitch-based carbon fibers being particularly preferred. When using the aforementioned carbon fibers, it is preferable from the viewpoint of thermal conductivity that the long axes of the carbon fibers 21 are oriented parallel to the thickness direction of the thermal conductive sheet 20, as shown in Figure 2. The content of the aforementioned thermally conductive substance is not particularly limited and can be appropriately selected depending on the purpose, but it is preferably 10% by mass or more and 90% by mass or less of the total amount of the resin composition.

[0026] -resin- There are no particular restrictions on the resins mentioned above, and they can be appropriately selected according to the purpose. Examples include polyethylene resin, polypropylene resin, ethylene-α-olefin copolymers such as ethylene-propylene copolymer; polymethylpentene resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyvinyl acetate resin, ethylene-vinyl acetate copolymer, polyvinyl alcohol resin, polyvinyl acetal resin, polyvinylidene fluoride resin, polytetrafluoroethylene and other fluorinated polymers; polyethylene terephthalate resin, polybutylene terephthalate resin, polyethylene naphthalate resin, polystyrene resin, polyacrylonitrile resin, styrene- Examples include acrylonitrile copolymers, acrylonitrile-butadiene-styrene copolymer (ABS) resins, polyphenylene-ether copolymer (PPE) resins, modified PPE resins, aliphatic polyamide resins, aromatic polyamide resins, polyimide resins, polyamide-imide resins, polymethacrylic acid, polymethacrylic acid esters such as polymethyl methacrylate; polyacrylic acid, polycarbonate resins, polyphenylene sulfide resins, polysulfone resins, polyethersulfone resins, polyethernitrile resins, polyetherketone resins, polyketone resins, liquid crystal polymers, silicone resins, epoxy resins, and ionomer resins. These may be used individually or in combination of two or more.

[0027] -solvent- As the solvent, the same solvent as the one used in the resin composition can be used.

[0028] The aforementioned other components are not particularly limited and can be appropriately selected depending on the purpose. Examples include thixotropy-imparting agents, dispersants, curing accelerators, retarders, tackifiers, plasticizers, flame retardants, antioxidants, stabilizers, and colorants.

[0029] The aforementioned thermal conductive composition may be one that has been appropriately manufactured or a commercially available product. There are no particular restrictions on the commercially available product, and it can be appropriately selected according to the purpose. Examples include silver paste (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., TS185sr) and silver paste (manufactured by Kaken Tech Co., Ltd., CR3520, CM3212). The silver paste is preferably one with a thermal conductivity of 10 W / m·K or higher, and can be used after being diluted with a solvent to a viscosity of 200 mPa·s or less at 25°C. If the adhesive strength of the thermal conductive composition is low, a conductive adhesive may be used together with the thermal conductive composition. When a conductive adhesive is used, the film thickness will be at least an order of magnitude thinner than that of the thermal conductive composition, so a thermal conductivity as high as that of the thermal conductive composition is not required, and a thermal conductivity of 1 W / m·K or higher is preferable.

[0030] The aforementioned thermally conductive composition is applied to the inside of the resin frame by an inkjet method. The wet film thickness of the aforementioned thermal conductive composition (liquid) is preferably 200 μm or less. The viscosity of the thermally conductive composition at 25°C is preferably 200 mPa·s or less, more preferably 100 mPa·s or less, and even more preferably 50 mPa·s or less. A viscosity of 200 mPa·s or less at 25°C has the advantage of being less prone to ejection defects when ejected by the inkjet method. The viscosity of the thermally conductive composition can be measured, for example, in accordance with JIS Z 8803. There are no particular restrictions on the apparatus used to measure the viscosity, and it can be appropriately selected according to the purpose. Examples include the TV25 type viscometer (cone plate type viscometer, manufactured by Toki Sangyo Co., Ltd.).

[0031] <Heating process> The heating step involves heating the liquid film and the resin frame to solidify the liquid film and foam the resin frame, and is performed using a heating means. The heating means is not particularly limited and can be appropriately selected depending on the purpose. Examples include hot air heaters, infrared heaters, and hot plates. In the heating step, the resin frame is heated to a temperature at which the foaming agent within the resin frame foams, causing the resin frame to foam and be removed from the adherend, while simultaneously solidifying the liquid film made of the thermally conductive composition (liquid). In this disclosure, solidification means that the liquid film hardens to the extent that it does not spread, and it is not necessary for the entire liquid film to harden completely. In this disclosure, solidification may be referred to as partial hardening. The heating in the aforementioned heating step is preferably carried out at a temperature of 100°C or higher but less than 160°C. Heating at 100°C or higher but less than 160°C allows the foaming agent in the resin frame to foam and the thermally conductive composition to solidify. The average thickness of the solidified liquid film is preferably 20 μm or more.

[0032] <Removal process> The removal process involves removing the resin frame. Since the aforementioned resin frame can be easily peeled off from the adherend by foaming upon heating, there is no need for a mechanical peeling process.

[0033] <Curing process> The curing process involves removing the resin frame and then heating the solidified liquid film to cure it. The heating in the curing process is preferably carried out at a temperature of 160°C to 200°C. In the curing process, a heat dissipation member such as a heat sink is placed on the surface of the solidified liquid film, and the liquid film is cured by heating in this state. This allows the heat dissipation member to be bonded and fixed onto the liquid film, thereby enabling the manufacture of a heat dissipation structure.

[0034] <Other processes> Other processes are not particularly limited and can be selected as appropriate depending on the purpose, such as cleaning processes and control processes.

[0035] The thermal conductive structure manufactured by the manufacturing method of the present invention is in the form of a sheet or film and can achieve high thermal conductivity. Therefore, it is suitable for use around various electrical devices such as CPUs, MPUs, power transistors, LEDs, laser diodes, and various batteries (various secondary batteries such as lithium-ion batteries, various fuel cells, capacitors, amorphous silicon, crystalline silicon, compound semiconductors, and various solar cells such as wet solar cells) where temperature can adversely affect the efficiency and lifespan of the element operation. It is also suitable for use around heat sources in heating equipment where effective use of heat is required, heat exchangers, and around heat piping in floor heating systems.

[0036] (Manufacturing method for heat dissipation structures) The method for manufacturing the heat dissipation structure of the present invention includes steps comprising the method for manufacturing the thermally conductive structure of the present invention, and further includes other steps as necessary. The heat dissipation structure comprises, for example, a heat-generating element such as an electronic component, a heat dissipation member such as a heat sink, heat pipe, or heat spreader, and a thermally conductive structure sandwiched between the heat-generating element and the heat dissipation member.

[0037] There are no particular restrictions on the aforementioned electronic components, and they can be appropriately selected according to the purpose. Examples include CPUs (Central Processing Units), MPUs (Micro Processing Units), and GPUs (Graphics Processing Units).

[0038] The heat dissipation structure is not particularly limited as long as it is a structure that dissipates the heat generated by electronic components (heat-generating elements), and can be appropriately selected according to the purpose. Examples include heat spreaders, heat sinks, vapor chambers, and heat pipes. The heat spreader is a component for efficiently transferring heat from the electronic component to other components. There are no particular restrictions on the material of the heat spreader, and it can be appropriately selected depending on the purpose, for example, copper, aluminum, etc. The heat spreader is usually in the shape of a flat plate. The heat sink is a component for releasing heat from the electronic component into the air. There are no particular restrictions on the material of the heat sink, and it can be appropriately selected depending on the purpose, for example, copper, aluminum, etc. The heat sink has, for example, a plurality of fins. The heat sink has, for example, a base portion and a plurality of fins provided so as to extend in a direction non-parallel to one surface of the base portion (for example, in a direction perpendicular to it). The heat spreader and the heat sink generally have a solid structure with no internal space. The vapor chamber is a hollow structure. A volatile liquid is sealed inside the hollow structure. Examples of the vapor chamber include a hollow heat spreader, a hollow heat sink, or a plate-shaped hollow structure. The heat pipe is a hollow structure that is cylindrical, substantially cylindrical, or flattened. A volatile liquid is sealed inside the hollow structure.

[0039] Here, Figure 1 is a schematic diagram of a semiconductor device as an example of a heat dissipation structure. This Figure 1 is a schematic cross-sectional view of an example of a semiconductor device. The heat conductive sheet 1, as a heat conductive structure, dissipates the heat generated by electronic components 3 such as semiconductor elements. As shown in Figure 1, it is fixed to the main surface 2a of the heat spreader 2 that faces the electronic components 3, and is sandwiched between the electronic components 3 and the heat spreader 2. The heat conductive sheet 1 is also sandwiched between the heat spreader 2 and the heat sink 5. Together with the heat spreader 2, the heat conductive sheet 1 constitutes a heat dissipation member that dissipates the heat from the electronic components 3.

[0040] The heat spreader 2 is formed, for example, in the shape of a rectangular plate and has a main surface 2a facing the electronic component 3 and side walls 2b erected along the outer circumference of the main surface 2a. The heat spreader 2 has a thermal conductive sheet 1 provided on the main surface 2a surrounded by the side walls 2b, and a heat sink 5 is provided on the other surface 2c opposite to the main surface 2a via the thermal 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 electronic components 3 such as semiconductor elements. For example, it can be formed using copper or aluminum, which have good thermal conductivity.

[0041] The electronic component 3 is, for example, a semiconductor element such as a BGA, and is mounted on the wiring board 6. The heat spreader 2 also has the leading edge of its side wall 2b mounted on the wiring board 6, thereby surrounding the electronic component 3 at a predetermined distance by the side wall 2b. Then, by bonding the thermal conductive sheet 1 to the main surface 2a of the heat spreader 2, a heat dissipation member is formed that absorbs the heat emitted by the electronic component 3 and dissipates the heat from the heat sink 5. The bonding between the heat spreader 2 and the thermal conductive sheet 1 can be achieved by the adhesive force of the thermal conductive sheet 1 itself.

[0042] Hereinafter, embodiments of the method for manufacturing the thermally conductive structure of the present invention will be described in detail with reference to the drawings. In each drawing, the same components are denoted by the same reference numerals, and redundant descriptions may be omitted. Furthermore, the number, position, shape, etc. of the components described below are not limited to this embodiment, and may be set to a number, position, shape, etc. that is preferable for carrying out the present invention.

[0043] <First Embodiment> Figures 3(A) to (C) are process diagrams showing an example of a method for manufacturing a thermally conductive structure according to the first embodiment. First, as shown in Figure 3(A), a resin frame 12 with a height of 200 μm is placed on the adherend 11 by a dispenser method using a resin composition containing p-toluenesulfonyl hydrazide (foaming temperature 110°C) as a foaming agent. Then, a silver paste (manufactured by Kaken Tech Co., Ltd., CR3520, pre-curing temperature: 130°C, viscosity at 25°C 200 mPa·s or less) is applied to the inside of the resin frame 12 as a thermally conductive composition 13a by an inkjet method to form a liquid film.

[0044] Next, as shown in Figure 3(B), the liquid film 13b and the resin frame 12 are heated to solidify the liquid film and cause the resin frame 12 to foam. When the liquid film 13b and the resin frame 12 are heated at 120°C, the liquid film solidifies and the resin frame foams.

[0045] Next, as shown in Figure 3(C), the resin frame 12 is removed, and a flat liquid film 13b of the desired thickness is formed on the adherend.

[0046] <Second Embodiment> Figures 4(A) to (E) are process diagrams showing an example of a method for manufacturing a thermally conductive structure according to the second embodiment.

[0047] As shown in Figures 4(A) and 4(B), a resin composition is applied to the adherend 11 to form a resin frame 12. Suitable methods for applying the resin composition include inkjet printing, dispenser printing, and screen printing, which allow for easy patterning.

[0048] As shown in Figure 4(C), a liquid film is formed on the inside of the resin frame 12 by applying a thermally conductive composition (liquid) 13a containing a thermally conductive substance using an inkjet method.

[0049] As shown in Figure 4(D), the liquid film 13b and the resin frame 12 are heated to solidify the liquid film and cause the resin frame 12 to foam, and then the resin frame 12 is removed.

[0050] As shown in Figure 4(E), a heat dissipation structure is obtained by placing a heat dissipation member 14 on the liquid film 13b and heating and curing the liquid film. When silver paste (CR3520, manufactured by Kaken Tech Co., Ltd.) is used as the thermally conductive composition 13a, the curing temperature is 180°C. Materials with high thermal conductivity such as aluminum, copper, and brass can be used as the material for the heat dissipation member. The outer casing can also serve as the heat dissipation member.

[0051] Examples of the present invention are as follows: <1> A resin frame forming step involves applying a resin composition containing a resin and a foaming agent to form a resin frame, A liquid film formation step involves applying a thermally conductive composition containing a thermally conductive substance to the inside of the aforementioned resin frame by an inkjet method to form a liquid film, A heating step in which the liquid film and the resin frame are heated to solidify the liquid film and foam the resin frame, A removal step of removing the aforementioned resin frame, This is a method for manufacturing a thermally conductive structure, characterized by including [a specific element]. <2> The process includes a curing step in which the solidified liquid film is heated and cured after the resin frame has been removed. <1> This is a method for manufacturing the thermally conductive structure described in [reference]. <3> The foaming temperature of the foaming agent is 200°C or lower. <1> from <2> This is a method for manufacturing a thermally conductive structure as described in any of the above. <4> The heating in the aforementioned heating step is performed at a temperature of 100°C or higher and less than 160°C. The heating in the curing process is performed at a temperature of 160°C or higher and 200°C or lower. <2> from <3> This is a method for manufacturing a thermally conductive structure as described in any of the above. <5> The viscosity of the thermally conductive composition at 25°C is 200 mPa·s or less. <1> from <4> This is a method for manufacturing a thermally conductive structure as described in any of the above. <6> The average thickness of the solidified liquid film is 20 μm or more. <1> from <5> This is a method for manufacturing a thermally conductive structure as described in any of the above. <7> The thermally conductive material is at least one selected from metal particles, boron nitride particles, aluminum oxide particles, and carbon fibers. <1> from <6> This is a method for manufacturing a thermally conductive structure as described in any of the above. <8> The resin frame is formed by an inkjet method, <1> from <7> This is a method for manufacturing a thermally conductive structure as described in any of the above. <9> The aforementioned <1> from <8> A method for manufacturing a heat dissipation structure, characterized by including a step comprising the method for manufacturing a heat conductive structure described in any of the above.

[0052] The aforementioned <1> from <8> A method for manufacturing a thermally conductive structure as described in any of the above, and the <9> The method for manufacturing the heat dissipation structure described herein can solve the problems of the conventional method and achieve the objectives of the present invention. [Explanation of symbols]

[0053] 1. Thermal conductive sheet 2 Heat spreader 2a Main surface 3. Heat-generating element (electronic component) 3a Top side 5 Heatsink 6 Wiring board 11 Adherent 12 Resin frame 13a Thermally conductive composition (liquid) 13b Liquid film 14 Heat dissipation components [Prior art documents] [Patent Documents]

[0054] [Patent Document 1] International Publication No. 2016 / 152660 Brochure [Patent Document 2] Japanese Patent Publication No. 2011-200839

Claims

1. A resin frame forming step involves applying a resin composition containing a resin and a foaming agent to form a resin frame, A liquid film formation step involves applying a thermally conductive composition containing a thermally conductive substance to the inside of the aforementioned resin frame by an inkjet method to form a liquid film, A heating step in which the liquid film and the resin frame are heated to solidify the liquid film and foam the resin frame, A removal step of removing the aforementioned resin frame, A method for manufacturing a thermally conductive structure, characterized by including [a certain element].

2. A method for manufacturing a thermally conductive structure according to claim 1, comprising a curing step of heating and hardening the solidified liquid film after removing the resin frame.

3. A method for manufacturing a thermally conductive structure according to any one of claims 1 to 2, wherein the foaming temperature of the foaming agent is 200°C or lower.

4. The heating in the heating step is performed at a temperature of 100°C or higher and less than 160°C. A method for manufacturing a thermally conductive structure according to claim 2, wherein the heating in the curing step is performed at a temperature of 160°C or higher and 200°C or lower.

5. A method for producing a thermally conductive structure according to any one of claims 1 to 4, wherein the viscosity of the thermally conductive composition at 25°C is 200 mPa·s or less.

6. A method for manufacturing a thermally conductive structure according to any one of claims 1 to 5, wherein the average thickness of the solidified liquid film is 20 μm or more.

7. A method for manufacturing a thermally conductive structure according to any one of claims 1 to 6, wherein the thermally conductive material is at least one selected from metal particles, boron nitride particles, aluminum oxide particles, and carbon fibers.

8. A method for manufacturing a thermally conductive structure according to any one of claims 1 to 7, wherein the resin frame is formed by an inkjet method.

9. A method for manufacturing a heat dissipation structure, characterized by including a step comprising the method for manufacturing a heat conductive structure according to any one of claims 1 to 8.

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