JP2020011509A - Method for selecting heat-conductive composite sheet for heat press bonding - Google Patents

Abstract

To provide a heat-conductive silicone rubber composite sheet for heat press bonding which controls curl at a very small level and is excellent in handleability even when a silicone rubber composition is laminated on only one surface of a heat-resistant resin film, and has such durability as to be hardly damaged even when bonding is repeatedly performed at the same portion, and a method for producing the same.SOLUTION: There is provided a heat-conductive composite sheet for heat bonding in which a silicone rubber layer formed of a cured product of a silicone rubber composition is laminated on one surface of a heat-resistant resin film, in which a thickness of the whole composite sheet is 100-400 μm, a thickness ratio represented by silicone rubber layer/heat-resistant resin film is 2-10, a thickness of the heat-resistant resin film is 20-50 μm, and a tensile elastic modulus in accordance with ASTM D-882 measurement method of the heat-resistant resin film is 4-20 GPa.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a thermoconductive composite sheet for thermocompression bonding, and more particularly to a thermocompression bonding sheet for forming a laminated board or a flexible substrate, or for thermocompression bonding for an anisotropic conductive film used for connecting electrodes of a liquid crystal display or the like. The present invention relates to a thermally conductive heat conductive composite sheet for thermocompression bonding suitable as a sheet and a method for producing the same.

  A sheet for forming a laminated board or a flexible printed board using a press forming machine, or an anisotropic conductive film used to connect the electrode terminals of a liquid crystal display and a flexible printed board on which a drive circuit is mounted, are heated by a crimping machine. A heat conductive sheet is used as a sheet for pressure bonding. Recently, the materials of flexible printed circuit boards and anisotropic conductive films have become high-temperature forming types, and the molding temperature has been rising to shorten the pressure bonding cycle and improve productivity. In addition, heat resistance and thermal conductivity as well as durability are required.

  By using carbon black having a volatile content of 0.5% by mass or less as a thermal conductivity imparting agent as such a thermally conductive sheet, heat resistance and thermal conductivity usable at 300 ° C. or more can be obtained. Has been proposed (Patent Document 1: Japanese Patent No. 4739009).

  Further, a silicone rubber sheet alone using metal silicon as a thermal conductivity imparting agent in addition to carbon black has been proposed. The object here is to provide a thermocompression-bonding silicone rubber sheet suitable for high-precision thermocompression bonding, which is used when press-fitting narrow-pitch lead electrodes in a liquid crystal display or the like via an anisotropic conductive film. (Patent Document 2: Japanese Patent No. 5058938).

  Although these thermal conductive silicone rubber sheets alone achieve their purpose, sheet users aiming to further improve productivity can reduce the number of sheet replacements or avoid line stoppage due to sheet breakage and use repeatedly. In order to increase the number of times, the use environment has become more severe.

  For this reason, silicone rubber alone has a limit in strength, and studies on compounding have been conducted. As a means therefor, it is known to form a composite with a heat-resistant resin film represented by a glass cloth or an aromatic polyimide film (Patent Document 3: Japanese Patent No. 3902558, Patent Document 4: Japanese Patent No. 30412113). However, compounding with a glass cloth is not suitable for high-precision thermocompression bonding with a narrow mesh structure of the cloth. On the other hand, when the composite sheet is combined with a heat-resistant resin film, the elongation of the composite sheet itself is as small as 10% or less, and it can be applied to a narrow pitch. However, if the silicone rubber composition is laminated on only one side and cured by heating, both the glass cloth and the film are smaller than the thermal shrinkage of silicone, so they curl strongly with the silicone rubber inside and handleability is very poor. Had the disadvantage of becoming worse. Further, when the silicone rubber composition is laminated on both sides of a glass cloth or a film and cured by heating, curling is suppressed, but the production process becomes longer and productivity is inferior to lamination on only one side.

  On the other hand, when a heat-resistant resin film such as polytetrafluoroethylene (PTFE) or aromatic polyimide that is resistant to deformation in the tensile direction is used alone, the pressure received from the heat tool for crimping at the time of crimping cannot be completely absorbed and uniform crimping cannot be performed. There is a case where a portion is generated or a contact with a body to be crimped occurs before the crimping, and the position is shifted. In addition, when the resin film is used alone, a mark remains on the film after the pressure bonding, and the same portion cannot be used repeatedly. Although the film itself is not damaged, it is considered to have poor durability.

Japanese Patent No. 4739009 Japanese Patent No. 5058938 Japanese Patent No. 3902558 Japanese Patent No. 3041213

  The present invention has been made in view of the above-mentioned problems of the prior art, and even when a silicone rubber composition is laminated on only one side of a heat-resistant resin film, curling is suppressed to a very small level, handling is excellent, and pressure bonding is performed at the same location. An object of the present invention is to provide a thermally conductive silicone rubber composite sheet for thermocompression bonding, which is extremely resistant to breakage even when repeatedly performed and has durability.

  The present inventors have conducted intensive studies to achieve the above object, and as a result, a heat conductive composite for thermocompression bonding in which a silicone rubber layer made of a cured product of a silicone rubber composition is laminated on one surface of a heat resistant resin film. The sheet has a total thickness of 100 to 400 μm, a thickness ratio of the silicone rubber layer / heat-resistant resin film of 2 to 10, a thickness of the heat-resistant resin film of 20 to 50 μm, and ASTM D By making the heat-conductive composite sheet for thermocompression bonding having a tensile modulus of 4 to 20 GPa based on -882 measurement method, the curl is extremely high even when the silicone rubber composition is laminated on only one surface of the heat-resistant resin film. The present inventors have found that a thermally conductive silicone rubber composite sheet for thermocompression bonding that is small and suppressed and has durability can be obtained, and the present invention has been accomplished.

Accordingly, the present invention provides the following composite sheet and a method for producing the same.
[1] A heat conductive composite sheet for thermocompression bonding in which a silicone rubber layer made of a cured product of a silicone rubber composition is laminated on one surface of a heat resistant resin film, and the total thickness of the composite sheet is 100. The thickness ratio of the silicone rubber layer / heat-resistant resin film is 2 to 10, the thickness of the heat-resistant resin film is 20 to 50 μm, and the ASTM D- A thermally conductive composite sheet for thermocompression bonding having a tensile modulus of 4 to 20 GPa based on a 882 measurement method.
[2]. The silicone rubber layer,
(A) an organopolysiloxane represented by the following average composition formula (I) and having an average degree of polymerization of 100 or more: 100 parts by mass;
R ¹ _a SiO _{(4-a) / 2} (I)
(In the formula, R ¹ is the same or different unsubstituted or substituted monovalent hydrocarbon group, and at least two in one molecule are an aliphatic unsaturated group. A is 1.95 to 2.05 It is a positive number.)
(B) one or more fillers selected from silica, zinc oxide, magnesium oxide, aluminum oxide, titanium oxide, carbon black and metal silicon: 10 to 1,000 parts by mass;
(C-1) Platinum-based catalyst: effective amount,
(C-2) An organohydrogenpolysiloxane containing a hydrogen atom bonded to at least two silicon atoms in one molecule: a cured product of a silicone rubber composition containing 0.1 to 20 parts by mass [1] ] The heat conductive composite sheet for thermocompression bonding as described in [1].
[3]. The heat-resistant resin film is at least one selected from aromatic polyimide, polyamide, polyamide imide, polyether sulfone, polyether imide, polyethylene naphthalate, polytetrafluoroethylene, and tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer. The heat-conductive composite sheet for thermocompression bonding according to [1] or [2], wherein the heat-resistant resin film is made of a seed, and the surface of the heat-resistant resin film is surface-treated by physical treatment or chemical treatment.
[4]. A method for producing a thermoconductive composite sheet for thermocompression bonding in which a silicone rubber layer made of a cured product of a silicone rubber composition is laminated on one surface of a heat-resistant resin film, and the sheet is formed by a two-roll or calender roll forming machine. A step of integrating the silicone rubber composition formed into a shape into a composite sheet by directly laminating it on a heat-resistant resin film, and heating the integrated composite sheet to 100 to 160 ° C. without applying external tension. The method for producing a thermoconductive composite sheet for thermocompression bonding according to any one of [1] to [3], comprising a step of curing.
[5]. A method for producing a thermoconductive composite sheet for thermocompression bonding in which a silicone rubber layer made of a cured product of a silicone rubber composition is laminated on one side of a heat-resistant resin film, and the heat-resistant resin film is diluted with a solvent. A step of coating the silicone rubber composition diluent so that the thickness when the solvent is volatilized is 50 to 380 μm, and a step of heat-curing the coated material to 100 to 160 ° C. without applying external tension. , [1]-The method for producing a thermally conductive composite sheet for thermocompression bonding according to any one of [3].
[6]. The solvent for diluting the silicone rubber composition is toluene or xylene, the amount of dilution is 30 to 500 parts by mass when the silicone rubber composition is 100 parts by mass, and the viscosity of the diluent is 3 at 25 ° C. The method for producing a thermally conductive composite sheet for thermocompression bonding according to [5], wherein the thickness is from 50 to 50 Pa · s.

  The heat-conductive silicone rubber composite sheet for thermocompression bonding of the present invention can transmit heat and apply pressure uniformly, and even when the silicone rubber composition is laminated on only one side of the heat-resistant resin film, the curl is extremely high. Because it is kept small, it can be manufactured without complicating the manufacturing process, is easy to handle, and is very hard to break even when repeatedly press-bonded at the same location, and has excellent durability for thermocompression bonding. Can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic sectional drawing of the heat conductive composite sheet for thermocompression bonding whose thickness ratio of the silicone rubber layer / heat-resistant resin film layer to laminate of this invention is in the range of 2-10. FIG. 2 is a schematic cross-sectional view of a thermally conductive composite sheet for thermocompression bonding in which the thickness ratio of the laminated silicone rubber layer / heat resistant resin film layer is close to 1 as compared with FIG. 1. FIG. 2 is a schematic cross-sectional view of a thermoconductive composite sheet for thermocompression bonding in which a silicone rubber layer having a thickness similar to that of FIG. BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram of calender molding which becomes an example of the manufacturing method of the heat conductive composite sheet for thermocompression bonding of this invention. It is a schematic diagram of a crimping durability test. It is the schematic which looked at the ACF test piece used for crimping durability test from the upper direction. It is a heat conductive composite sheet for thermocompression bonding in a non-curled state. It is a heat conductive composite sheet for thermocompression bonding in a curled state for comparison.

Hereinafter, the present invention will be described in detail.
The thermally conductive composite sheet for thermocompression bonding of the present invention is a thermoconductive composite sheet for thermocompression bonding in which a silicone rubber layer made of a cured product of a silicone rubber composition is laminated on one surface of a heat-resistant resin film. The thickness of the entire sheet of the composite sheet is 100 to 400 μm, the thickness ratio represented by the silicone rubber layer / heat-resistant resin film is 2 to 10, and the thickness of the heat-resistant resin film is 20 to 50 μm, Further, the thermal conductive composite sheet for thermocompression bonding has a tensile modulus of 4 to 20 GPa based on the ASTM D-882 measurement method.

[Thermal conductive composite sheet for thermocompression bonding]
The thickness of the entire composite sheet is in the range of 100 to 400 μm, preferably 100 to 300 μm. When the thickness of the entire composite sheet exceeds 400 μm, the curl suppressing power is weak and the thermal conductivity is insufficient. The width is not particularly limited, but is preferably in the range of 400 to 1,200 mm, and more preferably in the range of 500 to 1,100 mm.

  The state in which the sheet does not curl is apparent as shown in FIG. 7, but the state is defined in the present invention as follows. That is, the formed silicone rubber composite sheet is cut into a 300 mm square, and the heat-resistant resin film layer is naturally placed on the horizontal surface so that the lower surface / silicone rubber layer is on the upper surface without pressing the sheet or gluing the back surface. A sheet having a difference of 10 mm or less between a sheet edge and a horizontal plane caused by the sheet being warped upward when placed is defined as “no curl”. In the case of curling, the curl is rolled up with the silicone rubber layer inside (FIG. 8).

  The thickness ratio represented by the silicone rubber layer / heat resistant resin film is 2 to 10, preferably 2.5 to 10. The composite sheet includes a step of heating and curing at 100 to 160 ° C. by a molding method described later. However, the heat shrinkage differs between the silicone rubber and the heat-resistant resin film, and the force of shrinkage is larger because the silicone rubber is larger. Works and tries to curl with the silicone rubber layer inside. Lowering the heat curing temperature tends to suppress this, but causes a problem that the adhesiveness at the interface between the laminated silicone rubber layer and the heat-resistant resin film layer is reduced. The adhesiveness between the curl and the composite sheet interface is reciprocal, so that the silicone rubber layer / heat-resistant resin is laminated on both sides of the heat-resistant resin film layer to the same extent or laminated on only one side so that the curl does not occur structurally. Techniques for making the film layers the same, that is, making the thickness ratio as close as possible to 1 are known (FIGS. 2 and 3). However, by using a heat-resistant resin film having the characteristics described below, this thickness ratio can be in the range of 2 to 10 (FIG. 1). If it is less than 2, the silicone rubber layer is too thin to be able to completely absorb the steps of the object to be crimped when pressure-bonded, and it is difficult to transmit the pressure uniformly. If it exceeds 10, the silicone rubber layer is too thick, and the silicone rubber cannot resist the force of curling inward.

[Heat-resistant resin film]
Since the composite sheet of the present invention is used at a temperature of about 300 ° C. or higher, the heat-resistant resin film needs to have excellent mechanical strength and releasability at high temperatures. Therefore, as the heat-resistant resin, resin films such as aromatic polyimide, polyamide imide, polyamide (particularly aromatic polyamide), polyether sulfone, polyether imide, and polyethylene naphthalate having a glass transition point of 200 ° C. or higher; Fluororesin films such as polytetrafluoroethylene (PTFE) or a tetrafluoroethylene / perfluoroalkylvinyl ether copolymer (PFA) having a melting point of 300 ° C. or higher can be used.

  The thickness of the heat-resistant resin film used in the present invention is in the range of 20 to 50 μm, more preferably 20 to 40 μm. If the thickness is too small, the mechanical strength of the film itself is low, so that the film breaks during sheet formation or during use as a pressure-bonded sheet. In addition, the handleability of the film itself is poor, and wrinkles may occur during sheet formation, which may make it impossible to form the sheet neatly. If it is less than 20 μm, it is very difficult to obtain the non-curled composite sheet of the present invention. On the other hand, if it exceeds 50 μm, although it tends to be hard to curl, the heat transfer becomes poor due to the thick film, and the thermocompression bonding becomes insufficient, so that the function as the thermocompression sheet is deteriorated.

  Further, the tensile modulus of the heat-resistant resin film based on ASTM D-882 measurement method is 4 to 20 GPa. Even when a silicone rubber composite sheet having the same thickness and shape is produced, the curl becomes easier when the tensile elastic modulus is smaller than about 4 GPa, and the curl becomes very difficult when the tensile elastic modulus is larger. Since the tensile elasticity of the film can withstand the force of the silicone rubber having a large heat shrinkage to curl inward, a heat-resistant resin film having a thickness of 20 μm or more requires a tensile elasticity of 4 GPa or more. Conversely, below 20 μm, without a greater tensile modulus, the silicone rubber will not be able to resist the inward curling force. The opposing force generally exceeds 20 GPa, but it is difficult to obtain a film having a high elastic modulus exceeding 20 GPa on the market.

  Further, the surface of the heat-resistant resin film is preferably surface-treated. Because of the surface treatment, the adhesiveness with the interface of the silicone rubber to be laminated tends to be strong, so that even if the thermocompression bonding is repeated at the same location, the resin film and the silicone rubber are hardly peeled off from the interface, and the heat is reduced. The durability is improved as a sheet for pressure bonding. The surface treatment method is not particularly limited as long as the above object can be achieved. Examples of the physical treatment method include plasma treatment and corona treatment, and chemical treatment methods include primer treatment and chemical treatment. Here, the term “adhesiveness” means that a specific numerical value of the adhesive strength is not set, and that the coated layer does not peel off by rubbing with a finger or break during crimping. If surface treatment is not performed, it is necessary to introduce a technique for improving the adhesive strength at the film / rubber interface during the production of the composite sheet, which is not preferable because the process becomes complicated.

  These commercial products include Kapton (manufactured by Toray Dupont), Apical (manufactured by Kaneka Corporation), Upilex (manufactured by Ube Industries, Ltd.), and aromatic polyamide, which are commercially available as aromatic polyimides. Aramika (made by Asahi Kasei Corporation), Teflon (registered trademark, made by DuPont) commercially available as a fluororesin, and Nitoflon (made by Nitto Denko Corporation). As a commercially available product having a tensile modulus of 4 GPa or more, there is a Kapton EN type (100 EN, 150 EN, 200 EN, etc.). However, since commercially available products are generally non-surface-treated types, it is preferable to use surface-treated types, and they can be obtained relatively easily.

  In addition, a heat-resistant resin film that has been given thermal conductivity by adding carbon black, or a heat-resistant resin that has been given thermal conductivity by adding a thermally conductive powder such as aluminum oxide or magnesium oxide. Films can also be used. As a heat-resistant resin film provided with thermal conductivity, Kapton MT (trade name, manufactured by Toray Dupont Co., Ltd.) is commercially available.

[Silicone rubber layer]
The silicone layer laminated on the heat-resistant resin film is
(A) an organopolysiloxane represented by the following average composition formula (I) and having an average degree of polymerization of 100 or more: 100 parts by mass;
R ¹ _a SiO _{(4-a) / 2} (I)
(In the formula, R ¹ is the same or different unsubstituted or substituted monovalent hydrocarbon group, and at least two in one molecule are an aliphatic unsaturated group. A is 1.95 to 2.05 It is a positive number.)
(B) one or more fillers selected from silica, zinc oxide, magnesium oxide, aluminum oxide, titanium oxide, carbon black and metallic silicon: 10 to 1,000 parts by mass;
(C-1) Platinum-based catalyst: effective amount,
(C-2) An organohydrogenpolysiloxane containing at least two hydrogen atoms bonded to at least two silicon atoms in one molecule: a cured product of a silicone rubber composition containing 0.1 to 20 parts by mass. preferable.

The organopolysiloxane of the component (A) may be used alone or in combination of two or more having different viscosities, average polymerization degrees and compositions.
As the organopolysiloxane in the present invention, a diorganopolysiloxane having two or more vinyl groups having an average degree of polymerization of 100 or more is preferable. In the average composition formula (I), R ¹ is the same or different and is unsubstituted or substituted monovalent. Represents a hydrocarbon group, specifically, methyl group, ethyl group, alkyl group such as propyl group, cyclopentyl group, cycloalkyl group such as cyclohexyl group, vinyl group, alkenyl group such as allyl group, phenyl group, An aryl group such as a tolyl group or a halogenated hydrocarbon group in which these hydrogen atoms are partially substituted with a chlorine atom, a fluorine atom or the like is exemplified. It is preferred that 0.001 to 5 mol%, particularly 0.01 to 1 mol% of R ¹ is an alkenyl group.

  Generally, it is preferable that the main chain of the organopolysiloxane is composed of dimethylpolysiloxane units or that the main chain of the organopolysiloxane has a vinyl group, a phenyl group, a trifluoropropyl group or the like introduced. In addition, the terminal of the molecular chain only needs to be blocked with a triorganosilyl group or a hydroxyl group. Examples of the triorganosilyl group include a trimethylsilyl group, a dimethylvinylsilyl group, and a trivinylsilyl group. The average degree of polymerization is 100 or more, preferably 200 to 6,000, and more preferably 1,000 to 6,000. When the average degree of polymerization is less than 100, the mechanical strength after curing is inferior and becomes brittle. The average degree of polymerization is a value in terms of polystyrene measured by gel permeation chromatography (GPC).

The component (B) is added for the purpose of imparting reinforcement or thermal conductivity. In particular, the mechanical strength of silica can be improved by adding silica to an organopolysiloxane, which has extremely low strength as compared with other synthetic rubbers. Silica BET specific surface area of preferably 50 m ² / g or more, 100 to 400 m ² / g is more preferable. Examples include fumed silica (dry silica), precipitated silica (wet silica), and the like, and fumed silica (dry silica) containing less impurities is particularly preferable. Further, the silica surface may be subjected to a hydrophobic treatment with an organopolysiloxane, organosilane, chlorosilane, alkoxysilane, or the like. Examples of commercially available products include Aerosil 200, Aerosil 300, and Aerosil R972 (all manufactured by Nippon Aerosil Co., Ltd.). It is not necessary to use amorphous silica, and crystalline silica such as quartz may be added. Examples of commercially available products include Crystallite VX-S and Crystallite 5X (both manufactured by Tatsumori Corporation). The amount of silica added is not particularly limited, but is preferably from 5 to 300 parts by mass, more preferably from 10 to 250 parts by mass, per 100 parts by mass of the organopolysiloxane. If the amount is less than 5 parts by mass, a sufficient reinforcing effect may not be obtained. If the amount is more than 300 parts by mass, moldability may be deteriorated.

  Zinc oxide, magnesium oxide, aluminum oxide, titanium oxide, carbon black, and metallic silicon are added for the purpose of imparting thermal conductivity. Zinc oxide, magnesium oxide, aluminum oxide, titanium oxide, carbon black, and metal silicon may be added to the organopolysiloxane of the component (A) to form a compound or a master batch, or a silicone rubber directly in powder form It may be added to the composition. The average particle size is preferably from 1 to 50 μm, more preferably from 1 to 30 μm. If the average particle size exceeds 50 μm, the smoothness of the sheet may be impaired, and pressure may not be transmitted uniformly to thermocompression bonding. If it is less than 1 μm, the viscosity or plasticity of the rubber composition after addition tends to increase, and the moldability may deteriorate. The average particle size is a value measured as a mass average value D50 in the particle size distribution measurement by the laser light diffraction method.

  As commercially available fillers, conductive zinc white (Zinc oxide manufactured by Honjo Chemical Co., Ltd.), AL-24 (aluminum oxide manufactured by Showa Denko KK), LS-210BS (aluminum oxide manufactured by Nippon Light Metal Co., Ltd.), AX10-32R (Aluminum oxide manufactured by Micron Corporation), Crystallite VXS (described above, crystalline silica manufactured by Tatsumori Corporation), MSR series (Silica manufactured by Tatsumori Corporation), P-25 (Nippon Aerosil ( Titape R-820 (Titanium oxide manufactured by Ishihara Sangyo Co., Ltd.), Denka Black (Acetylene Black manufactured by Denka Co., Ltd.), Ketjen Black (Carbon Black manufactured by Lion Specialty Chemicals Co., Ltd.), Meta Siri series (metal silicon manufactured by Kinsei Matech Co., Ltd.) and the like are exemplified.

  Generally, carbon black is classified into a furnace method, a channel method, a thermal method (including an acetylene black method) and the like when classified according to a production method. The furnace method is a method in which creosote oil or the like is partially burned in a refractory room in a space surrounded by appropriate turbulent diffusion, and then water droplets are cooled, and carbon produced by this method is used. It is called furnace black, and the channel method is a method in which a diffusion flame is partially burned in an unenclosed space and collides with a cold surface (channel plate). The carbon produced by this method is called channel black, and the thermal method Is a method in which a checker construction of refractory brick is sufficiently heated and the raw material is thermally decomposed or a method similar thereto, and the carbon produced by this method is referred to as thermal black, and particularly in the thermal method. Among them, carbon produced by a production method by exothermic decomposition in a space surrounded by acetylene is called acetylene black. In producing carbon black in this way, carbon black except acetylene black produced by burning acetylene gas is produced by burning raw materials derived from petroleum, and as a result, sulfur is contained as an impurity. It often happens. The content thereof is, for example, about 0.5% by mass in the case of FEF (Fast Extruding Furnace) grade carbon. It is known that this impurity causes the curing inhibition of the addition crosslinking reaction, and acetylene black is preferably used as carbon black.

  The total addition amount of the component (B) is 10 to 1,000 parts by mass, more preferably 15 to 800 parts by mass, and still more preferably 20 to 600 parts by mass, per 100 parts by mass of the organopolysiloxane of the component (A). Parts by weight. If the amount is less than 10 parts by mass, sufficient effects may not be obtained for imparting thermal conductivity or reducing the tackiness of the sheet surface, and when the amount is more than 1,000 parts by mass, moldability may be deteriorated.

  The curing agent of the component (C) is an addition reaction curing agent by a hydrosilylation reaction. Examples of the addition reaction curing agent include a hydrosilylation reaction comprising (C-1) a platinum catalyst and (C-2) an organohydrogenpolysiloxane containing at least two hydrogen atoms bonded to one silicon atom in one molecule. The combination which can be hardened by is used.

  The addition amount of these may be an effective amount as in the case of ordinary silicone rubber, but (C-1) is based on 100 parts by mass of the organopolysiloxane having at least two alkenyl groups of the component (A). The amount of the component) is preferably 1 to 2,000 ppm, more preferably 1 to 100 ppm. When a platinum-based catalyst is further used for imparting flame retardancy, a large amount may be blended. The amount of the component (C-2) is 0.1 to 20 parts by mass, but the amount of the SiH group is 0.5 to 5 mol% based on the amount of the alkenyl group of the component (A). The amount is preferably, and more preferably 0.5 to 2 mol%.

  In the present invention, heat resistance can be further improved by adding cerium oxide powder or iron oxide powder to the silicone rubber composition. The addition amount is preferably in the range of 0.1 to 5 parts by mass based on 100 parts by mass of the component (A). Even if it exceeds 5 parts by mass, the heat resistance does not improve according to the amount added.

  In the silicone rubber composition used in the present invention, if necessary, fillers such as clay, calcium carbonate, diatomaceous earth, low molecular siloxane esters, dispersants such as low molecular siloxanes containing silanol groups, silane coupling agents, titanium An adhesion imparting agent such as a coupling agent, tetrafluoropolyethylene particles for increasing the green strength of the rubber compound, and the like may be added. When a dispersant is blended, the amount is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the component (A). The silicone rubber composition used in the present invention may be kneaded using a two-roller, a kneader, a Banbury mixer, a planetary mixer, or another mixer. The curing agent is preferably added immediately before use, but when the silicone rubber composition is dispersed in a solvent, it is preferably added at least before the dispersion of the solvent.

[Method of manufacturing composite sheet]
Depending on the method of forming the composite sheet, there is a range of thickness that can be easily formed. The molding method includes (1) a method of dispensing a silicone rubber composition containing a curing agent into a predetermined thickness with a two-roll, calender, or extruder, followed by heat curing, and (2) a liquid silicone rubber. A method of coating the composition or a silicone rubber composition dissolved in an organic solvent such as toluene or xylene and liquefied on a carrier film and then curing the composition is mentioned.

  When the silicone rubber composition to be laminated is cured by heating, it is necessary to carry out the curing at 100 to 160 ° C. The molding temperature of the composite sheet is preferably formed at a lower temperature in order to suppress curling, but the adhesion between the silicone rubber layer and the heat-resistant resin film of the produced composite sheet is stronger as the molding is performed at a higher temperature. Tends to be. As the adhesiveness between the silicone rubber layer and the film becomes stronger, the number of times of repeated use, that is, the durability tends to be improved.

(1) A step of integrating a silicone rubber composition formed into a sheet into a composite sheet by directly laminating the silicone rubber composition on a heat-resistant resin film using a two-roll or calender roll molding machine. A method for producing a thermally conductive composite sheet for thermocompression bonding, comprising a step of heating and curing at 100 to 160 ° C. without applying tension from the outside. Further, the method may include a step of directly forming the cured composite sheet into a take-up roll.

  An example of a method of calendering the silicone rubber composition will be described with reference to FIG. In the present invention, the heat-resistant resin film also directly serves as a carrier film. A silicone rubber composition in which a curing agent has been previously compounded is prepared. First to fifth rolls are arranged in the calender roll device 11, and the silicone rubber composition 12 is dispensed to a predetermined thickness by the calender roll. The silicone rubber composition is directly laminated on the heat-resistant resin film 15 from between the third roll 13 and the fourth roll 14 and integrated therewith. Subsequently, the obtained laminate 16 is heated and cured in a vulcanizer 17 at 100 to 160 ° C., preferably 110 to 150 ° C. for 5 to 30 minutes, preferably 10 to 20 minutes without applying tension. By doing so, the composite sheet 18 can be obtained. Although the total thickness of the obtained composite sheet 18 can be produced in the range of 100 to 400 μm, production in the thickness range of 120 to 380 μm is more preferable. The composite sheet 18 is rolled by a winding device 19.

(2) coating the heat-resistant resin film with the liquid silicone rubber composition or the diluted silicone rubber composition diluted with a solvent so that the thickness when the solvent is volatilized becomes 50 to 380 μm; A method for producing a thermally conductive composite sheet for thermocompression bonding, comprising a step of heating and curing a coating at 100 to 160 ° C. without applying tension from the outside. Further, the method may include a step of directly forming the cured composite sheet into a take-up roll.

  A method of coating a liquid silicone rubber composition or a silicone composition solution liquefied by dissolving in an organic solvent onto a heat-resistant resin film includes a blade coater, a knife coater, a reverse roll coater, a gravure coater, a spray coater, and the like. However, a blade coater and a knife coater are preferred. The solvent is not particularly limited as long as it is an organic solvent capable of dissolving the organopolysiloxane, but toluene or xylene is preferable. The dilution amount is preferably in the range of 30 to 500 parts by mass, and more preferably 50 to 500 parts by mass, when the silicone rubber composition is 100 parts by mass.

  The factor that determines the concentration is the viscosity of the solution, and its viscosity range depends on the coating equipment. The factor that determines the viscosity range is the thickness of the silicone layer (= coating) when laminated. For example, when adjusting to 3 to 50 Pa · s when coating with a comma coater (manufactured by Hirano Techseed Co., Ltd.), the thickness of the coating film can be controlled in the range of 10 to 200 μm. Therefore, even when the silicone rubber composition is diluted with an organic solvent, the viscosity of the solution is preferably 3 to 50 Pa · s at 25 ° C. measured by a rotational viscometer. Thus, after applying the silicone rubber composition, the coating film is dried and heat-cured at 100 to 160 ° C., preferably 110 to 150 ° C. for 5 to 30 minutes, preferably 10 to 20 minutes. Thus, a composite sheet can be obtained. Although the total thickness of the obtained composite sheet can be manufactured in the range of 100 to 400 μm, the manufacture in the thickness range of 100 to 200 μm is more preferable.

  Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Production of silicone rubber compound]
99.825 mol% of dimethylsiloxane unit ((CH ₃ ) ₂ SiO _2/2 ), 0.15 mol% of methylvinylsiloxane unit ((CH ₂ ＣＨCH) (CH ₃ ) SiO _2/2 ), dimethylvinylsiloxy unit ((CH ₂ ＣＨCH) (CH ₃ ) SiO _1/2 ) 0.025 mol%, an organopolysiloxane having an average degree of polymerization of about 6,000, and a dimethylsiloxane unit ((CH ₃ ) ₂ SiO ₂ ) _{/ 2} ) 99.675 mol%, methyl vinyl siloxane unit ((CH ₂ ＣＨCH) (CH ₃ ) SiO _2/2 ) 0.30 mol%, dimethyl vinyl siloxy unit ((CH ₂ ＣＨCH) (CH ₃ ) SiO _1/2) consists 0.025 mol%, by blending an organopolysiloxane average degree of polymerization of about 6,000, a vinyl group content was adjusted to the range of 0.205 to 0.215 mol% 100 parts by mass of luganopolysiloxane, 160 parts by mass of silica (crystallite: VXS, manufactured by Tatsumori Co., Ltd.), 30 parts by mass of carbon black (Denka Black, manufactured by Denka Co., Ltd.), a silicon atom as a dispersant and a hydroxyl group And 0.5 parts by mass of an organopolysiloxane having an average degree of polymerization of about 20 to which a vinyl group was bonded, and kneaded with a Banbury mixer for about 10 minutes to obtain Compound A.

Also, 99.825 mol% of a dimethylsiloxane unit ((CH ₃ ) ₂ SiO _2/2 ), 0.15 mol% of a methylvinylsiloxane unit ((CH ₂ ＣＨCH) (CH ₃ ) SiO _2/2 ), An organopolysiloxane comprising 0.025 mol% of siloxy units ((CH ₂ ＣＨCH) (CH ₃ ) SiO _1/2 ) having an average degree of polymerization of about 6,000, and a dimethylsiloxane unit ((CH ₃ ) ₂ SiO _2/2) 99.675 mol%, methylvinylsiloxane units _{((CH 2 = CH) (} CH 3) SiO 2/2) 0.30 mol%, dimethylvinylsiloxy units _{((CH 2 = CH) (} CH ₃ ) An organopolysiloxane composed of 0.025 mol% of SiO _1/2 ) having an average degree of polymerization of about 6,000 is blended so that the vinyl group content is in the range of 0.220 to 0.230 mol%. Key 100 parts by mass of the obtained organopolysiloxane, 220 parts by mass of crystallite (trade name: VXS, manufactured by Tatsumori Co., Ltd.), and an organopolysiloxane having a hydroxyl atom and a vinyl group bonded to a silicon atom as a dispersant and having an average degree of polymerization of about 20. 0.6 parts by mass was added and kneaded with a Banbury mixer for about 10 minutes to obtain Compound B.

[Example 1]
2.0 parts by mass of C-19A (platinum catalyst, manufactured by Shin-Etsu Chemical Co., Ltd.) as a vulcanizing agent for Compound A obtained by the above-mentioned production method, C-8 (peroxide paste, Shin-Etsu Chemical Co., Ltd.) 1A) to which 1.0 part by mass of Co., Ltd. was added. Further, a composition 1B was obtained by adding 4.0 parts by mass of C-19B (organohydrogensiloxane) (manufactured by Shin-Etsu Chemical Co., Ltd.) as a vulcanizing agent to Compound A.
The obtained compositions 1A and 1B were uniformly kneaded with equal amounts using two rolls to obtain composition 1. The composition 1 was used as a base material, and a 1,000 mm-wide plasma-treated polyimide film (25 μm thick, tensile modulus 5.8 GPa product) was directly placed on the polyimide film using a calendering machine. The layers were adjusted to a thickness of 150 μm and laminated. Linear velocity 2.0 m / min. The maximum temperature of the vulcanizing line was set to 150 ° C. to obtain a composite sheet 1.

Hereinafter, a composite sheet is obtained in the same manner as in Example 1, but different points from Example 1 and the like will be described. The polyimide films are all plasma surface-treated products.
[Example 2]
Polyimide film: 38 μm thickness, tensile elastic modulus: 5.8 GPa Product sheet thickness: 150 μm (same as in Example 1)

[Example 3]
Polyimide film: 25 μm thick, tensile modulus 4.4 GPa Product sheet overall thickness: 150 μm (same as in Example 1)

[Example 4]
Polyimide film: 25 μm thick, tensile modulus 5.8 GPa Product sheet overall thickness: 250 μm

[Example 5]
Polyimide film: 38 μm thick, 5.8 GPa tensile modulus (same as in Example 2)
Sheet overall thickness: 250 μm (same as Example 4)

[Example 6]
Polyimide film: 50 μm thick, tensile elastic modulus: 5.8 GPa Product thickness: 250 μm (same as in Example 4)

[Example 7]
Polyimide film: 50 μm thick, tensile modulus 8.8 GPa Product sheet overall thickness: 350 μm

Example 8
Polyimide film: 50 μm thick, tensile modulus of elasticity 16 GPa Sheet overall thickness: 350 μm (same as in Example 7)

[Comparative Example 1]
Polyimide film: 25 μm thickness, tensile elasticity 3.4 GPa Product sheet thickness: 150 μm (same as in Example 1)

[Comparative Example 2]
Polyimide film: 38 μm thick, tensile modulus 3.4 GPa Product sheet overall thickness: 150 μm (same as in Example 1)

[Comparative Example 3]
Polyimide film: 38 μm thickness, tensile elasticity 3.4 GPa Product overall thickness: 250 μm (same as Example 4)

[Comparative Example 4]
Polyimide film: 75 μm thick, tensile modulus: 5.8 GPa Product sheet overall thickness: 250 μm (same as in Example 4)

[Comparative Example 5]
Polyimide film: 38 μm thick, 5.8 GPa tensile modulus (same as in Example 2)
Sheet thickness: 450 μm

[Example 9]
2.0 parts by mass of C-19A (platinum-based catalyst, manufactured by Shin-Etsu Chemical Co., Ltd.) and C-8 (peroxide paste, Shin-Etsu Chemical Co., Ltd.) as a vulcanizing agent for Compound B obtained by the above-mentioned production method The composition to which 1.0 part by mass was added was dissolved in 100 parts by mass of toluene to obtain a composition 2A. Further, a composition obtained by adding 2.0 parts by mass of C-19B (organohydrogensiloxane, manufactured by Shin-Etsu Chemical Co., Ltd.) as a vulcanizing agent to compound A and 0.4 parts by mass of black color paste for color tone adjustment was added. The composition was dissolved in 100 parts by mass of toluene to obtain a composition 2B.
The obtained compositions 2A and 2B were added in equal amounts, and dispersed uniformly to obtain a coating liquid 2. The coating liquid 2 was applied as a base material onto a 400 mm-wide plasma-treated polyimide film (25 μm thick, tensile modulus 5.8 GPa) using a comma coater (described above). The gap was adjusted so that the dry coating film thickness was 112 μm, and firstly, a linear velocity of 0.4 m / min. The maximum temperature of the vulcanizing line was set to 140 ° C., and the composite sheet 9 was obtained so that the thickness of the entire sheet became 150 μm.

Hereinafter, a composite sheet is obtained in the same manner as in Example 9, but different points from Example 9 and the like will be described. The polyimide films are all plasma surface-treated products.
[Example 10]
Polyimide film: 38 μm thick, 5.8 GPa tensile modulus (same as in Example 2)
Sheet thickness: 150 μm (same as in Example 9)

[Example 11]
Polyimide film: 25 μm thick, 4.4 GPa tensile modulus (same as in Example 3)
Sheet thickness: 150 μm (same as in Example 9)

[Example 12]
Polyimide film: 50 μm thick, tensile modulus of 16 GPa (same as in Example 8)
Sheet thickness: 150 μm (same as in Example 9)

[Comparative Example 6]
Polyimide film: 12 µm thick, tensile modulus 3.4 GPa Product sheet overall thickness: 50 µm

[Comparative Example 7]
Polyimide film: 12 μm thick, tensile modulus 5.8 GPa Product sheet thickness: 50 μm

[Comparative Example 8]
Polyimide film: 25 μm thickness, tensile elasticity 3.4 GPa Product sheet thickness: 50 μm

[Comparative Example 9]
Polyimide film: 25 μm thickness, tensile elasticity 3.4 GPa Product sheet overall thickness: 75 μm

[Comparative Example 10]
Polyimide film: 25 μm thickness, tensile elastic modulus: 5.8 GPa Product thickness: 75 μm

[Comparative Example 11]
Polyimide film: 25 μm thickness, tensile elasticity 3.4 GPa Product sheet thickness: 150 μm

[Comparative Example 12]
Polyimide film: 38 μm thickness, tensile modulus 3.4 GPa Product sheet thickness: 150 μm

[Comparative Example 13]
Polyimide film: 75 μm thickness, tensile modulus: 5.8 GPa Product thickness: 150 μm

[Comparative Example 14]
Polyimide film: 25 μm thick, 5.8 GPa tensile modulus (same as in Example 9)
Sheet thickness: 450 μm

[Evaluation method]
The evaluation as a heat- and heat-conductive composite sheet was performed using the following tester.
Tester A: Thermal pressure evaluation tester manufactured by Osaki Engineering Co., Ltd. The crimping part shape of the pressurized steel heat tool used was 10 mm × 30 mm.
Testing machine B: Full crimping machine CBM-16 manufactured by Ohashi Manufacturing Co., Ltd. The shape of the pressure-bonded portion of the steel heat tool for pressurization used was 1 mm × 40 mm.
The set temperature, crimping time, pressure applied to the crimping portion, and the number of times of crimping were set for each test.

(Sheet curl)
When the formed composite sheet is cut into 300 mm squares and the heat-resistant resin film layer is naturally placed on a horizontal surface with the lower surface / silicone rubber layer on the upper surface without pressing the sheet or gluing the back surface, A sheet having a difference of 10 mm or less between a sheet edge and a horizontal plane caused by the sheet being warped upward was judged as “○: no curl”. In addition, the sheet in which the silicone rubber layer was rolled inward in the form of a roll was marked as x, and the sheet which was not completely rolled but had a difference from the horizontal plane exceeding 10 mm due to the sheet warping upward was marked as Δ.

(Thermal conductivity)
It is determined whether heat can be transmitted efficiently as a thermocompression bonding sheet. The set temperature of the heat tool of the tester A was 300 ° C., the crimping time was 20 seconds, the pressure applied to the crimping part was 3 MPa, and the number of times of crimping was one. To a sheet piece cut out to 30 mm x 50 mm, the temperature transmitted through the sheet piece was measured using a sheet thermocouple, and those reaching the range of 180 to 220 ° C after 5 seconds were evaluated as ○, and those outside the above range were evaluated as ×. .

(Crimping durability)
It is determined whether the composite sheet can be repeatedly used as a thermocompression bonding sheet. FIG. 5 shows a schematic view of the crimping durability test. Using a temporary crimping machine ABM-42 manufactured by Ohashi Seisakusho Co., Ltd., a 20 mm long anisotropic conductive film (Acrylic type ACF21, manufactured by Hitachi Chemical Co., Ltd.) is temporarily crimped on a glass plate having a thickness of 50 mm × 50 mm × 5 mm (= ACF). (Anisotropic conductive film) Test piece 22). Further, the composite sheet 18 is cut out into a size of 200 mm × 10 mm and set on a tester B such that the heat-resistant resin film (polyimide) side is the heat tool side. The set temperature of the heat tool 23 of the testing machine B was 350 ° C., the pressure bonding time was 10 seconds, and the pressure applied to the pressure bonding portion was 4 MPa. The ACF test piece 22 is set on the stage of the tester B such that the heat tool 23 directly hits the ACF 21 via the composite sheet. The ACF test piece 22 itself was replaced each time as a single press, but the composite sheet 18 was repeatedly pressed until the sheet components adhered to the ACF 21 of the ACF test piece 22 or the composite sheet 18 itself was damaged. (FIGS. 5 and 6). When the number of times of press bonding was 50 or more, it was evaluated as ○, and when less than 50 times, it was evaluated as ×.

  The results are shown in the table below. Those judged to be suitable for the present invention were OK, and those judged to be unsuitable were NG.

REFERENCE SIGNS LIST 1 heat conductive composite sheet for thermocompression bonding 2 silicone rubber layer 3 heat resistant resin film 11 calender roll device 12 silicone rubber composition 13 third roll 14 fourth roll 15 heat resistant resin film 16 laminate 17 vulcanizing device 18 composite sheet 19 Winding device 20 Glass plate 21 ACF
22 ACF (anisotropic conductive film) test piece 23 Heat tool

Claims (2)

  A method for selecting a thermally conductive composite sheet for thermocompression bonding in which a silicone rubber layer made of a cured product of a silicone rubber composition is laminated on one surface of a heat-resistant resin film, wherein the thickness of the composite sheet is 100 The thickness ratio of the silicone rubber layer / heat-resistant resin film is 2 to 10, the thickness of the heat-resistant resin film is 20 to 50 μm, and the ASTM D-882 measurement method of the heat-resistant resin film is used. Selection method for selecting a tensile modulus of elasticity of 4 to 20 GPa based on the above.   The heat-resistant resin film is a heat-resistant resin film having a glass transition point of 200 ° C. or higher or a melting point of 300 ° C. or higher. (The crimping part shape of the steel heat tool is 10 mm × 30 mm) The set temperature of the heat tool is 300 ° C., the crimping time is 20 seconds, the pressure applied to the crimping part is 3 MPa, the number of times of crimping is one, and the composite sheet is 30 mm × The selection method according to claim 1, wherein when the temperature transmitted through the sheet piece is measured using a sheet thermocouple on a sheet piece cut out to 50 mm, the temperature reaches a range of 180 to 220C after 5 seconds.