CN107662383B

CN107662383B - Thermally conductive composite sheet for thermocompression bonding and method for producing same

Info

Publication number: CN107662383B
Application number: CN201710620830.8A
Authority: CN
Inventors: 宇野贵雄; 米山勉
Original assignee: Shin Etsu Chemical Co Ltd
Current assignee: Shin Etsu Chemical Co Ltd
Priority date: 2016-07-27
Filing date: 2017-07-27
Publication date: 2022-04-29
Anticipated expiration: 2037-07-27
Also published as: KR20180012700A; JP6627681B2; KR102457695B1; TWI715790B; CN107662383A; TW201815571A; JP2018016710A

Abstract

The invention provides a thermally conductive composite sheet for thermocompression bonding, which has extremely small curl, excellent handling property, and durability, and is extremely difficult to break even if pressure bonding is repeated at the same position, even if a silicone rubber composition is laminated only on one side of a heat-resistant resin film, and a method for manufacturing the same. A thermal conductive composite sheet for thermocompression bonding, which is obtained by laminating a silicone rubber layer formed by a cured product of a silicone rubber composition on one surface of a heat-resistant resin film, wherein the thickness of the whole sheet of the composite sheet is 100-400 [ mu ] m, the thickness ratio represented by the silicone rubber layer/the heat-resistant resin film is 2-10, the thickness of the heat-resistant resin film is 20-50 [ mu ] m, and the tensile elastic modulus of the heat-resistant resin film measured by ASTM D-882 is 4-20 GPa.

Description

Thermally conductive composite sheet for thermocompression bonding and method for producing same

Technical Field

The present invention relates to a thermal conductive composite sheet for thermocompression bonding, and more particularly to a thermal conductive composite sheet for thermocompression bonding which is suitable as a thermal conductive composite sheet for thermocompression bonding used for forming a laminate or a flexible substrate, or for connecting electrodes of a liquid crystal display or the like, and which is thermally conductive, and a method for producing the same.

Background

A heat conductive sheet is used as a sheet when a laminate board or a flexible printed board is molded by a press molding machine, or a sheet when an anisotropic conductive film used for connecting a flexible printed board on which an electrode terminal portion and a driver circuit of a liquid crystal display are mounted is thermocompression bonded by a press bonding machine. Recently, materials for flexible printed boards and anisotropic conductive films have been molded at high temperatures, and thermal conductive sheets are required to have durability as well as heat resistance and thermal conductivity in order to shorten the bonding cycle, improve productivity, and increase the molding temperature.

As such a heat conductive sheet, a single silicone rubber sheet has been proposed which has heat resistance and heat conductivity that can be used at 300 ℃ or higher by using carbon black having a volatile content other than moisture of 0.5 mass% or less as a heat conductivity-imparting agent (patent document 1: japanese patent No. 4739009).

In addition, a single silicone rubber sheet using metal silicon as a thermal conductivity-imparting agent in addition to carbon black has also been proposed. An object of the present invention is to provide a silicone rubber sheet for thermocompression bonding suitable for high-precision thermocompression bonding, which is used when bonding lead electrodes having a narrow pitch in a liquid crystal display or the like via an anisotropic conductive film (patent document 2: japanese patent No. 5058938).

Although these single heat conductive silicone rubber sheets have achieved their objects, the sheet users who aim to further improve productivity want to increase the number of times of repeated use without reducing the number of times of sheet replacement or stopping the production line due to sheet breakage, and therefore the use environment becomes severer.

Therefore, the silicone rubber alone has a limit in strength, and studies have been made to combine the silicone rubber and the silicone rubber. As a method for this, it is known to form a composite with a glass cloth or a heat-resistant resin film represented by an aromatic polyimide film (patent document 3: japanese patent No. 3902558, patent document 4: japanese patent No. 3041213). However, in the case of the composite with the glass cloth, the mesh structure of the cloth is not suitable for high-precision thermocompression bonding due to the narrow pitch. On the other hand, in the case of the composite with a heat-resistant resin film, the elongation of the composite sheet itself is as small as 10% or less, and a narrow pitch can be coped with. However, if the silicone rubber composition is laminated only on one side and cured by heating, the thermal shrinkage of both the glass cloth and the film is smaller than that of silicone, and therefore, there is a disadvantage that the silicone rubber becomes inside and strongly curls, and the handling property is very poor. In addition, in the case where the silicone rubber composition is laminated on both surfaces of the glass cloth or film and cured by heating, although curling is suppressed, the production process is extended compared with the case where the silicone rubber composition is laminated only on one surface, and productivity is poor.

On the other hand, if a heat-resistant resin film such as Polytetrafluoroethylene (PTFE) or aromatic polyimide, which resists deformation in the stretching direction, is used alone, pressure applied from a heating tool for pressure bonding is not completely absorbed during pressure bonding, and a portion which cannot be uniformly pressure bonded is generated, and the pressure bonded body is hit before pressure bonding, or the position is shifted, and therefore, the pressure bonded body may be pressure bonded with a shift from a target position. In addition, if the resin film is used alone, a trace remains on the film after pressure bonding, and the same portion cannot be used repeatedly. Although the film itself was not broken, it was positioned to have poor durability.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 4739009

Patent document 2: japanese patent No. 5058938

Patent document 3: japanese patent No. 3902558

Patent document 4: japanese patent No. 3041213

Disclosure of Invention

Problems to be solved by the invention

In view of the problems of the prior art described above, an object of the present invention is to provide a thermally conductive silicone rubber composite sheet for thermocompression bonding that has extremely low curling, excellent handling properties, and durability, and is extremely unlikely to break even when the silicone rubber composition is laminated only on one side of the heat-resistant resin film, and that is also extremely resistant to repeated pressure bonding at the same location, and a method for producing the same.

Means for solving the problems

The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that: the present inventors have found that a thermocompression bonding thermoconductive composite sheet obtained by laminating a silicone rubber layer formed by a cured product of a silicone rubber composition on one side of a heat-resistant resin film is 100 to 400 [ mu ] m thick, the thickness ratio of the silicone rubber layer to the heat-resistant resin film is 2 to 10, the heat-resistant resin film is 20 to 50 [ mu ] m thick, and the tensile elastic modulus of the heat-resistant resin film is 4 to 20GPa as measured by ASTM D-882, and that a thermocompression bonding thermoconductive silicone rubber composite sheet having extremely small curling and durability can be obtained even when a silicone rubber composition is laminated on only one side of a heat-resistant resin film, and have completed the present invention.

Accordingly, the present invention provides the following composite sheet and a method for producing the same.

[1] A thermocompression bonding thermal conductive composite sheet is formed by laminating a silicone rubber layer containing a cured product of a silicone rubber composition (or composed of a cured product of a silicone rubber composition) on one surface of a heat-resistant resin film, wherein the thickness of the entire sheet of the composite sheet is 100 to 400 [ mu ] m, the thickness ratio expressed by the silicone rubber layer/the heat-resistant resin film is 2 to 10, the thickness of the heat-resistant resin film is 20 to 50 [ mu ] m, and the tensile elastic modulus of the heat-resistant resin film measured by ASTM D-882 is 4 to 20 GPa.

[2] The thermally conductive composite sheet for thermocompression bonding according to [1], wherein the silicone rubber layer is a cured product of a silicone rubber composition containing:

(A) an organopolysiloxane having an average degree of polymerization of 100 or more, represented by the following average composition formula (I): 100 parts by mass of a water-soluble polymer,

R¹ _aSiO_(4-a)/2 (I)

(in the formula, R¹Are identical or different unsubstituted or substituted monovalent hydrocarbon radicals, and at least 2 of 1 molecule are aliphatically unsaturated radicals. a is a positive number of 1.95 to 2.05. )

(B) 1 or more fillers selected from silica, zinc oxide, magnesium oxide, alumina, titanium oxide, carbon black and metallic silicon: 10 to 1,000 parts by mass,

(C-1) platinum group catalyst: an effective amount of a compound of formula (I),

(C-2) an organohydrogenpolysiloxane containing at least 2 silicon atom-bonded hydrogen atoms in 1 molecule: 0.1 to 20 parts by mass.

[3] The thermal conductive composite sheet for thermocompression bonding according to [1] or [2], wherein the heat-resistant resin film is composed of at least 1 selected from the group consisting of aromatic polyimide, polyamide, polyamideimide, polyethersulfone, polyetherimide, polyethylene naphthalate, polytetrafluoroethylene, and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and a surface of the heat-resistant resin film is subjected to a surface treatment by a physical treatment or a chemical treatment.

[4] The method for producing a thermal conductive composite sheet for thermocompression bonding according to any one of [1] to [3], which is a method for producing a thermal conductive composite sheet for thermocompression bonding in which a silicone rubber layer composed of a cured product of a silicone rubber composition is laminated on one surface of a heat-resistant resin film, comprising: a step of laminating the silicone rubber composition molded into a sheet shape directly on a heat-resistant resin film by using a twin-roll or calender roll molding machine to integrate the silicone rubber composition into a composite sheet; and a step of heating and curing the integrated composite sheet at 100 to 160 ℃ without applying tension from the outside.

[5] The method for producing a thermal conductive composite sheet for thermocompression bonding according to any one of [1] to [3], which is a method for producing a thermal conductive composite sheet for thermocompression bonding in which a silicone rubber layer composed of a cured product of a silicone rubber composition is laminated on one surface of a heat-resistant resin film, comprising: a step of applying a diluted solution of the silicone rubber composition diluted with a solvent onto a heat-resistant resin film so that the thickness of the resin film when the solvent is volatilized is 50 to 380 [ mu ] m; and a step of heating and curing the coated product at 100 to 160 ℃ without applying tension from the outside.

[6] [5] the method for producing a thermal conductive composite sheet for thermocompression bonding, wherein a solvent for diluting the silicone rubber composition is toluene or xylene, the amount of dilution is 30 to 500 parts by mass per 100 parts by mass of the silicone rubber composition, and the viscosity of a dilution liquid is 3 to 50 pas at 25 ℃.

ADVANTAGEOUS EFFECTS OF INVENTION

The thermally conductive silicone rubber composite sheet for thermocompression bonding of the present invention can uniformly apply pressure while transferring heat, and can suppress curl to a very small extent even if a silicone rubber composition is laminated only on one side of a heat-resistant resin film, and therefore can provide a thermocompression bonding sheet which can be produced without complicating the production process, has excellent handling properties, is very difficult to break even when pressure bonding is repeated at the same site, and has excellent durability.

Drawings

FIG. 1 is a schematic cross-sectional view of a thermal conductive composite sheet for thermocompression bonding, in which the thickness ratio of the laminated silicone rubber layer/heat-resistant resin film layer is in the range of 2 to 10.

Fig. 2 is a schematic cross-sectional view of a thermal 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. 3 is a schematic cross-sectional view of a thermal conductive composite sheet for thermocompression bonding in which silicone rubber layers having the same thickness are laminated on both surfaces as compared with fig. 1.

Fig. 4 is a schematic view of roll forming, which is an example of the method for producing a thermal conductive composite sheet for thermocompression bonding according to the present invention.

Fig. 5 is a schematic diagram of the crimping durability test.

Fig. 6 is a schematic view of an ACF test piece used in the pressure-bonding durability test, as viewed from above.

Fig. 7 shows a thermocompression bonding thermal conductive composite sheet in a state without curling.

Fig. 8 shows a thermal conductive composite sheet for thermocompression bonding in a relatively curled state.

Description of reference numerals

1 Heat conductive composite sheet for thermocompression bonding

2 Silicone rubber layer

3 Heat-resistant resin film

11 calendering roll device

12 Silicone rubber composition

13 rd roll

14 th roller

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 heating tool

Detailed Description

The present invention will be described in detail below.

The thermal conductive composite sheet for thermocompression bonding is obtained by laminating a silicone rubber layer composed of a cured product of a silicone rubber composition on one surface of a heat-resistant resin film, wherein the thickness of the whole sheet of the composite sheet is 100 to 400 [ mu ] m, the thickness ratio represented by the silicone rubber layer/the heat-resistant resin film is 2 to 10, the thickness of the heat-resistant resin film is 20 to 50 [ mu ] m, and the tensile elastic modulus measured by ASTM D-882 is 4 to 20 GPa.

[ Heat-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. If the thickness of the entire composite sheet exceeds 400 μm, the curl suppression force is weak and the thermal conductivity is insufficient. The width is not particularly limited, but is preferably in the range of 400 to 1,200mm, and more preferably in the range of 500 to 1,100 mm.

The state in which the sheet is not curled is clear in appearance as shown in fig. 7, but the state is defined as follows in the present invention. That is, when the molded silicone rubber composite sheet was cut to a 300mm square and placed on a horizontal plane in a natural state without pressing the sheet or without applying a back surface paste so that the heat-resistant resin film layer was the lower surface and the silicone rubber layer was the upper surface, the difference between the sheet end portion and the horizontal plane, which is caused by the sheet warping upward, was set to "no curl" when the difference was 10mm or less. When the silicone rubber layer is curled, the silicone rubber layer is curled inward and is curled (fig. 8).

The thickness ratio of the silicone rubber layer/the heat-resistant resin film is 2 to 10, preferably 2.5 to 10. The composite sheet is formed by a molding method described later, which includes a step of heat curing at 100 to 160 ℃, but the silicone rubber and the heat-resistant resin film have different heat shrinkage rates, and the silicone rubber has a large heat shrinkage rate, so that a force of shrinkage acts, and the silicone rubber layer is curled inward. The heat curing temperature is lowered, and thus the heat curing temperature tends to be suppressed, but there is a problem that the adhesiveness at the interface of the laminated silicone rubber layer/heat-resistant resin film layer is lowered. The curl is opposite to the adhesiveness at the interface of the composite sheet, and in order to prevent the curl from occurring in the structure, a method is known in which the heat-resistant resin film layers are laminated to the same extent on both sides, or the silicone rubber layer/the heat-resistant resin film layer laminated to the same extent even on only one side, that is, the thickness ratio is infinitely close to 1 (fig. 2 and 3). However, by using a heat-resistant resin film having the properties described later, the thickness ratio can be set to a range of 2 to 10 (fig. 1). If the thickness is less than 2, the silicone rubber layer is thin, and may not sufficiently absorb the step height difference of the object to be pressure-bonded during pressure bonding, and may not sufficiently satisfy the function as a pressure-bonding sheet, for example, it may be difficult to uniformly transmit the pressure. If it exceeds 10, the silicone rubber layer is too thick to sufficiently resist the force of the silicone rubber to curl inward.

[ Heat-resistant resin film ]

The heat-resistant resin film is required to have excellent mechanical strength, releasability and the like at high temperatures because the composite sheet of the present invention is used at temperatures around 300 ℃. Therefore, as the heat-resistant resin, a resin film such as an aromatic polyimide, a polyamide (particularly an aromatic polyamide), a polyamideimide, a polyethersulfone, a polyetherimide, or a polyethylene naphthalate having a glass transition temperature of 200 ℃ or higher, or a fluororesin film such as Polytetrafluoroethylene (PTFE) or a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) having a melting point of 300 ℃ 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, and more preferably 20 to 40 μm. If the thickness is too thin, the mechanical strength of the film itself is small, and therefore, the film is broken when the sheet is molded or when the sheet is used as a pressure-bonded sheet. Further, the film itself is poor in handling property, and wrinkles are generated at the time of sheet molding, and the sheet cannot be molded neatly. If it is less than 20 μm, it is very difficult to obtain the composite sheet of the present invention without curling. On the other hand, if it exceeds 50 μm, curling tends to be difficult, but since the film is thick, heat conduction is poor, thermocompression bonding becomes insufficient, and the function as a thermocompression bonding sheet is lowered.

The heat-resistant resin film has a tensile elastic modulus of 4 to 20GPa as measured by ASTM D-882. Even when silicone rubber composite sheets having the same thickness and shape are produced, the tensile elastic modulus is limited to about 4GPa, and the sheet tends to curl easily when small, and is extremely difficult to curl when large. In order to make the tensile elastic modulus of the film capable of resisting the force of the silicone rubber having a large thermal contraction to curl inward, it is necessary that the tensile elastic modulus of the heat-resistant resin film of 20 μm or more is 4GPa or more. Conversely, if it is less than 20 μm, if it does not have a larger tensile modulus of elasticity, the force with which the silicone rubber is to be curled inward cannot be sufficiently resisted. The forces that can be resisted exceed about 20GPa, but it is difficult for the market to obtain films with high elastic modulus exceeding 20 GPa.

Further, the surface of the heat-resistant resin film is preferably subjected to a surface treatment. Since the surface treatment is performed, the adhesiveness to the interface of the laminated silicone rubber is easily strengthened, and therefore, even if thermocompression bonding is repeated at the same portion, the resin film and the silicone rubber are less likely to peel off from the interface, and the durability as a thermocompression bonding sheet is improved. The method of surface treatment is not particularly limited as long as the above object can be achieved, and physical treatment methods include plasma treatment, corona treatment, and the like, and chemical treatment methods include primer treatment, chemical treatment, and the like. Here, the adhesion property does not set a specific numerical target of the adhesion strength, and indicates that the applied layer is not peeled off by finger wiping or is not broken when pressure-bonded. When the surface treatment is not performed, it is necessary to introduce a method for improving the adhesive strength at the film/rubber interface in the production of the composite sheet, and the process is not preferable because the process is complicated.

Commercially available products of these include Kapton (manufactured by Toho DuPont), Apical (manufactured by Kazai Kagaku Kogyo Co., Ltd.), Upi lex (manufactured by Uyu Kyoki Co., Ltd.), aramitan (manufactured by Asahi Kagaku Kogyo Co., Ltd.), teflon (registered trademark, manufactured by DuPont) and NITOFLON (manufactured by Nindon electrician Co., Ltd.), which are commercially available as aromatic polyimides. Further, Kapton EN type (100EN, 150EN, 200EN, etc.) is available as a commercial product having a tensile elastic modulus of 4GPa or more. However, since commercially available products are generally of a non-surface-treated type, the surface-treated type is preferably used and can be obtained relatively easily.

Further, a heat-resistant resin film to which electrical conductivity is imparted by blending carbon black, or a heat-resistant resin film to which thermal conductivity is imparted by blending a thermally conductive powder such as alumina or magnesia can be used. As a heat-resistant resin film to which thermal conductivity is imparted, Kapton MT (trade name, manufactured by tokyo corporation) is commercially available.

[ Silicone rubber layer ]

The silicone layer laminated on the heat-resistant resin film is preferably a cured product of a silicone rubber composition containing:

R¹ _aSiO_(4-a)/2 (I)

(A) The organopolysiloxane of component (a) can be used alone in 1 kind, or 2 or more kinds different in viscosity, average polymerization degree, and composition can be used in combination.

As the organopolysiloxane in the present invention, preferred is FlatA diorganopolysiloxane having 2 or more vinyl groups and an average degree of polymerization of 100 or more, R in the average composition formula (I)¹The monovalent hydrocarbon groups may be the same or different and may be unsubstituted or substituted, and specifically, there may be exemplified alkyl groups such as methyl, ethyl and propyl, cycloalkyl groups such as cyclopentyl and cyclohexyl, alkenyl groups such as vinyl and allyl, aryl groups such as phenyl and tolyl, and halogenated hydrocarbon groups in which hydrogen atoms thereof are partially substituted with chlorine atoms, fluorine atoms, and the like. Preferably R¹0.001 to 5 mol%, particularly 0.01 to 1 mol% of (A) is an alkenyl group.

In general, it is preferable that the main chain of the organopolysiloxane is composed of a dimethylpolysiloxane unit or that a vinyl group, a phenyl group, a trifluoropropyl group, or the like is introduced into the main chain of the organopolysiloxane. In addition, the molecular chain terminals may be terminated with triorganosilyl groups or hydroxyl groups. 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, more preferably 1,000 to 6,000. When the average polymerization degree is less than 100, the mechanical strength after curing is poor and the cured product becomes brittle. The average polymerization degree is a polystyrene equivalent value obtained by Gel Permeation Chromatography (GPC).

The component (B) is added for the purpose of imparting reinforcing properties or thermal conductivity. In particular, the mechanical strength can be improved by adding silica to an organopolysiloxane having a strength very weak compared to other synthetic rubbers. The BET specific surface area of the silica is preferably 50m²More than g, preferably 100 to 400m²(ii) in terms of/g. Examples thereof include fumed silica (dry silica) and precipitated silica (wet silica), and fumed silica (dry silica) containing a small amount of impurities is particularly preferable. Further, the surface of silica may be subjected to hydrophobic treatment with organopolysiloxane, organosilane, chlorosilane, alkoxysilane, or the like. Examples of commercially available products include AEROSIL 200, AEROSIL 300, and AEROSIL R972 (all manufactured by Japan AEROSIL Co., Ltd.). Further, amorphous silica is not necessarily required, and crystalline silica such as quartz may be added. Examples of commercially available products include CRYSTALITE VX-S, CRYSTALITE 5X (all of Toxon (R.) Toxon)Manufacturing), and the like. The amount of the silica to be added is not particularly limited, but is preferably 5 to 300 parts by mass, and more preferably 10 to 250 parts by mass, based on 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, and if the amount is more than 300 parts by mass, moldability may be deteriorated.

In addition, zinc oxide, magnesium oxide, aluminum oxide, titanium oxide, carbon black, and metallic silicon are added to impart thermal conductivity. The zinc oxide, magnesium oxide, aluminum oxide, titanium oxide, carbon black, and metallic silicon may be added to the organopolysiloxane of component (a) to prepare a compound or a master batch, or may be added directly to the silicone rubber composition in the form of powder. The average particle diameter is preferably 1 to 50 μm, more preferably 1 to 30 μm. If the average particle size exceeds 50 μm, the smoothness of the sheet may be impaired, and the pressure may not be uniformly transmitted to the thermal compression bonding. If the particle diameter 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 diameter is a value measured as a mass average value D50 in particle size distribution measurement by a laser diffraction method.

Commercially available fillers include conductive zinc oxide (zinc oxide produced by this Hon jo CHEMICAL CORPORATION), Al-24 (aluminum oxide produced by Showa Denko K.K.), LS-210BS (aluminum oxide produced by Nippon light metals K.K.), AX10-32R (aluminum oxide produced by Micron Inc.), CRYSTALITE VXS (crystalline silica produced by Toxon K.K.), MSR series (silica produced by Toxon K.K.), P-25 (titanium oxide produced by Nippon AEROSIL K.K.), TIPAQUE R-820 (titanium oxide produced by Ketobao K.K., K.K.), DENKA BLACK (acetylene BLACK produced by DENKA K.K.), Ketjen BLACK (Lion Specialty Co., carbon BLACK produced by Ltdly), Metallic Silicon series (KINSEI MATEC CO., LTD. Metallic Silicon), and THE like.

Generally, carbon blacks are classified into furnace method, tank method, thermal cracking method (including acetylene black method) and the like, if they are classified according to the production method. The furnace method is a method of burning a part of a space surrounded by a proper turbulent diffusion of a creosote oil in a refractory chamber and then cooling the spray with water, and the carbon produced by this method is called furnace black, the channel method is a method of burning a diffusion flame part in a space not surrounded and making it collide with a cold surface (channel plate), the carbon produced by this method is called channel black, the thermal method is a method of heating a checker-patterned building of a firebrick sufficiently and thermally decomposing a raw material therein or a method similar thereto, the carbon produced by this method is called thermal black, and particularly the carbon produced by a production method of thermally decomposing in a space surrounded by acetylene in the thermal method is called acetylene black. In the production of carbon black in this way, carbon black other than acetylene black produced by burning acetylene gas is produced by burning a petroleum-derived raw material, and as a result, sulfur is contained in a large amount as an impurity. The content thereof is, for example, about 0.5 mass% for fef (fast Extruding furnace) grade carbon. It is known that such impurities cause inhibition of curing particularly in addition crosslinking reaction, and therefore acetylene black is preferably used as the 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, based on 100 parts by mass of the organopolysiloxane of the component (A). If the amount is less than 10 parts by mass, sufficient effects may not be obtained in imparting thermal conductivity and reducing the sticky feeling on the sheet surface, and if the amount is more than 1,000 parts by mass, moldability may be deteriorated.

(C) The curing agent of component (A) is an addition reaction curing agent using a hydrosilylation reaction. As the addition reaction curing agent, a combination of (C-1) a platinum group catalyst and (C-2) an organohydrogenpolysiloxane containing at least 2 silicon atom-bonded hydrogen atoms in 1 molecule, which can be cured by a hydrosilylation reaction, is used.

The amount of these additives may be an effective amount as in the case of ordinary silicone rubber, but the amount of the component (C-1) is preferably 1 to 2,000ppm, more preferably 1 to 100ppm, based on 100 parts by mass of the organopolysiloxane having at least 2 alkenyl groups of the component (A). Further, when a platinum-based catalyst is used for further imparting flame retardancy, a large amount of the catalyst can be blended. The amount of the component (C-2) is 0.1 to 20 parts by mass, and the amount of the SiH group is preferably 0.5 to 5 mol%, more preferably 0.5 to 2 mol%, based on the amount of the alkenyl group of the component (A). Further, a peroxide may be blended in the silicone rubber composition. In this case, the amount is preferably 0.1 to 0.6 part by mass.

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

The silicone rubber composition used in the present invention may contain, as necessary, fillers such as clay, calcium carbonate and diatomaceous earth, dispersants such as low-molecular siloxane esters and silanol group-containing low-molecular siloxanes, tackifiers such as silane coupling agents and titanium coupling agents, polytetrafluoroethylene particles for improving the green strength of the rubber compound, and the like. When a dispersant is blended, it is preferably 0.1 to 10 parts by mass per 100 parts by mass of the component (A). Further, the silicone rubber composition used in the present invention can be compounded by kneading the above components using a mixer such as a twin roll, a kneader, a banbury mixer, a planetary mixer, or the like. In the case where the curing agent is preferably added immediately before use to disperse the silicone rubber composition in the solvent, it is preferably added at least before the solvent dispersion is performed.

[ method for producing composite sheet ]

Depending on the molding method of the composite sheet, there is a range of thickness in which molding is easy. Examples of the molding method include: (1) a method in which a silicone rubber composition containing a curing agent is heated and cured after being separated into a predetermined thickness by a twin roll, a calender roll, or an extruder; (2) a method of coating a liquid silicone rubber composition or a silicone rubber composition dissolved and liquefied in an organic solvent such as toluene or xylene on a carrier film and then curing the coated silicone rubber composition.

The laminated silicone rubber composition is heated and cured at 100 to 160 ℃. The molding temperature of the composite sheet is preferably lower in order to suppress curling, but the adhesiveness between the silicone rubber layer and the heat-resistant resin film of the produced composite sheet tends to be stronger as the molding is performed at higher temperatures. The stronger the adhesion between the silicone rubber layer and the film, the more the number of repeated use, i.e., the durability tends to be improved.

As the method (1), there is a method for producing a thermal conductive composite sheet for thermocompression bonding, which comprises: a step of laminating the silicone rubber composition molded into a sheet shape directly on a heat-resistant resin film by using a twin-roll or calender roll molding machine to integrate the silicone rubber composition into a composite sheet; and a step of heating and curing the integrated composite sheet at 100 to 160 ℃ without applying a tension from the outside. Further, the method may further include a step of directly winding the cured composite sheet into a roll.

An example of a method for roll forming a silicone rubber composition will be described with reference to fig. 4. In the present invention, the heat-resistant resin film also directly plays a role of a carrier film. A silicone rubber composition containing a curing agent is prepared in advance. The 1 st to 5 th rolls are arranged in the calender roll device 11, and the silicone rubber composition 12 is divided into a predetermined thickness by using calender rolls. The heat-resistant resin film 15 is passed between the 3 rd roll 13 and the 4 th roll 14, and the silicone rubber composition is directly laminated on the film to be integrated therewith. Next, the obtained laminate 16 is cured by heating at 100 to 160 ℃, preferably 110 to 150 ℃ for 5 to 30 minutes, preferably 10 to 20 minutes, without applying tension in a curing device 17, thereby obtaining a composite sheet 18. The thickness of the entire composite sheet 18 obtained can be in the range of 100 to 400 μm, but the thickness is more preferably in the range of 120 to 380 μm. The composite sheet 18 is rolled by a winding device 19.

As the method (2), there is a method for producing a thermal conductive composite sheet for thermocompression bonding, which comprises: a step of applying a liquid silicone rubber composition or a dilution of the silicone rubber composition diluted with a solvent onto a heat-resistant resin film so that the thickness of the film when the solvent has evaporated is 50 to 380 [ mu ] m; and heating and curing the coated product at 100 to 160 ℃ without applying tension from the outside. Further, the method may further include a step of directly winding the cured composite sheet into a roll.

Examples of the method for applying the heat-resistant resin film with the liquid silicone rubber composition or the silicone composition solution dissolved and liquefied in the organic solvent include a blade coater, an inverse roll coater, a gravure coater, and a spray coater, and the blade coater are preferable. The solvent is not particularly limited as long as it is an organic solvent that dissolves the organopolysiloxane, and toluene or xylene is preferred. The amount of dilution is preferably in the range of 30 to 500 parts by mass, more preferably 50 to 500 parts by mass, per 100 parts by mass of the silicone rubber composition.

The main factor determining the concentration is the viscosity of the solution, the range of which depends on the application apparatus. The main factor determining the viscosity range is the thickness of the silicone layer (i.e., coating film) at the time of lamination. For example, when the thickness of the coating film is adjusted to 3 to 50Pa · s in coating with a corner-lacking wheel coater (HIRANO TECSEED co., ltd.), the thickness of the coating film can be controlled within a range of 10 to 200 μm. Therefore, when the silicone rubber composition is diluted with an organic solvent, it is also preferable that the viscosity of the solution is 3 to 50Pa · s at 25 ℃ as measured by a rotational viscometer. After the silicone rubber composition is coated in this way, the coating film is dried and cured by heating at 100 to 160 ℃, preferably 110 to 150 ℃ for 5 to 30 minutes, preferably 10 to 20 minutes, thereby obtaining a composite sheet. The thickness of the entire composite sheet obtained can be in the range of 100 to 400 μm, but the thickness in the range of 100 to 200 μm is more preferable.

Examples

The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the examples.

[ production of Silicone rubber Compound ]

Will consist of dimethylsiloxane units ((CH)₃)₂SiO_2/2)99.825 mol%, methyl vinyl siloxane units ((CH)₂＝CH)(CH₃)SiO_2/2)0.15 mol% ((CH))₂＝CH)(CH₃)SiO_1/2)0.025 mol% organopolysiloxane having an average degree of polymerization of about 6,000And a dimethylsiloxane unit ((CH)₃)₂SiO_2/2)99.675 mol%, methyl vinyl siloxane units ((CH)₂＝CH)(CH₃)SiO_2/2)0.30 mol%, dimethylvinylsiloxy unit ((CH)₂＝CH)(CH₃)SiO_1/2) An organopolysiloxane having a composition of 0.025 mol% and an average degree of polymerization of about 6,000, 100 parts by mass of an organopolysiloxane having a vinyl group content adjusted to a range of 0.205 to 0.215 mol%, silica (CRYSTALITE: the resulting mixture was kneaded using a banbury mixer for about 10 minutes, under the trade name of VXS, (manufactured by lonson corporation) 160 parts by mass, carbon BLACK (manufactured by DENKA BLACK, DENKA), 30 parts by mass, and 0.5 part by mass of an organopolysiloxane having hydroxyl groups and vinyl groups bonded to silicon atoms and having an average polymerization degree of about 20 as a dispersant, to obtain compound a.

In addition, will consist of dimethylsiloxane units ((CH)₃)₂SiO_2/2)99.825 mol%, methyl vinyl siloxane units ((CH)₂＝CH)(CH₃)SiO_2/2)0.15 mol% ((CH))₂＝CH)(CH₃)SiO_1/2)0.025 mol% of an organopolysiloxane having an average degree of polymerization of about 6,000, and dimethylsiloxane units ((CH)₃)₂SiO_2/2)99.675 mol%, methyl vinyl siloxane units ((CH)₂＝CH)(CH₃)SiO_2/2)0.30 mol%, dimethylvinylsiloxy unit ((CH)₂＝CH)(CH₃)SiO_1/2) An organopolysiloxane having a composition of 0.025 mol% and an average degree of polymerization of about 6,000, 100 parts by mass of an organopolysiloxane having a vinyl group content adjusted to a range of 0.220 to 0.230 mol%, and silica (CRYSTALITE: trade name VXS, (manufactured by lonson corporation) 220 parts by mass, and 0.6 part by mass of an organopolysiloxane having hydroxyl groups and vinyl groups bonded to silicon atoms as a dispersant and having an average degree of polymerization of about 20 were kneaded with a banbury mixer for about 10 minutes to obtain compound B.

[ example 1]

To the compound A obtained by the above-mentioned production method, 2.0 parts by mass of C-19A (manufactured by platinum group catalyst, shin-Etsu chemical Co., Ltd.) and 1.0 part by mass of C-8 (manufactured by peroxide paste, shin-Etsu chemical Co., Ltd.) were added as vulcanizing agents to obtain a composition 1A. Further, a composition 1B in which 4.0 parts by mass of C-19B (organohydrogensiloxane) (manufactured by shin-Etsu chemical Co., Ltd.) was added as a vulcanizing agent to the compound A was obtained.

The obtained compositions 1A and 1B were kneaded uniformly with equal amounts using a twin roll to obtain composition 1. Composition 1 was laminated on a 1,000 mm-wide polyimide film (product of 25 μm thickness and tensile elastic modulus of 5.8 GPa) subjected to plasma surface treatment as a base material, directly on the polyimide film by a calender roll molding machine so that the thickness of the entire sheet became 150 μm. The linear velocity was set to 2.0m/min, and the set temperature of the vulcanization line was set to 150 ℃ at maximum, to obtain a composite sheet 1.

Hereinafter, a composite sheet was obtained in the same manner as in example 1, and the differences from example 1 and the like were shown. The polyimide film is entirely a plasma surface-treated product.

[ example 2]

Polyimide film: 38 mu m thick product with tensile elastic modulus of 5.8GPa

Overall sheet thickness: 150 μm (same as in example 1)

[ example 3]

Polyimide film: 25 mu m thick product with tensile elastic modulus of 4.4GPa

Overall sheet thickness: 150 μm (same as in example 1)

[ example 4]

Polyimide film: 25 mu m thick product with tensile elastic modulus of 5.8GPa

Overall sheet thickness: 250 μm

[ example 5]

Polyimide film: 38 μm thick, 5.8GPa tensile modulus of elasticity (same as in example 2)

Overall sheet thickness: 250 μm (same as in example 4)

[ example 6]

Polyimide film: 50 mu m thick product with tensile elastic modulus of 5.8GPa

Overall sheet thickness: 250 μm (same as in example 4)

[ example 7]

Polyimide film: 50 mu m thick product with tensile elastic modulus of 8.8GPa

Overall sheet thickness: 350 μm

[ example 8]

Polyimide film: 50 μm thick, 16GPa tensile modulus of elasticity

Overall sheet thickness: 350 μm (same as in example 7)

Comparative example 1

Polyimide film: 25 mu m thick product with tensile elastic modulus of 3.4GPa

Overall sheet thickness: 150 μm (same as in example 1)

Comparative example 2

Polyimide film: 38 mu m thick product with tensile elastic modulus of 3.4GPa

Overall sheet thickness: 150 μm (same as in example 1)

Comparative example 3

Polyimide film: 38 mu m thick product with tensile elastic modulus of 3.4GPa

Overall sheet thickness: 250 μm (same as in example 4)

Comparative example 4

Polyimide film: 75 μm thick product with tensile elastic modulus of 5.8GPa

Overall sheet thickness: 250 μm (same as in example 4)

Comparative example 5

Overall sheet thickness: 450 μm

[ example 9]

A composition prepared by adding 2.0 parts by mass of C-19A (manufactured by platinum-based catalyst, shin-Etsu chemical Co., Ltd.) and 1.0 part by mass of C-8 (manufactured by peroxide paste, shin-Etsu chemical Co., Ltd.) as vulcanizing agents to the compound B obtained by the above-mentioned production method was dissolved in 100 parts by mass of toluene to obtain a composition 2A. Further, a composition in which 2.0 parts by mass of C-19B (organohydrogensiloxane, manufactured by shin-Etsu chemical Co., Ltd.) as a vulcanizing agent and 0.4 part by mass of a black coloring paste for color tone adjustment were added to the compound A 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 uniformly dispersed to obtain coating liquid 2. Coating liquid 2 was applied to a 400 mm-wide plasma surface-treated polyimide film (25 μm-thick product having a tensile elastic modulus of 5.8 GPa) as a substrate using a notched wheel coater (described above). The gap was adjusted so that the dried coating film thickness became 112 μm, and the composite sheet 9 was obtained so that the thickness of the entire sheet became 150 μm at a line speed of 0.4m/min on one side and a set temperature of the vulcanization line of 140 ℃ at maximum.

A composite sheet was obtained in the same manner as in example 9, and the differences from example 9 and the like were shown below. The polyimide film is entirely a plasma surface-treated product.

[ example 10]

Overall sheet thickness: 150 μm (same as in example 9)

[ example 11]

Polyimide film: 25 μm thick, 4.4GPa tensile modulus (same as in example 3)

Overall sheet thickness: 150 μm (same as in example 9)

[ example 12]

Polyimide film: 50 μm thick, 16GPa tensile modulus of elasticity (same as in example 8)

Overall sheet thickness: 150 μm (same as in example 9)

Comparative example 6

Polyimide film: 12 μm thick product with tensile elastic modulus of 3.4GPa

Overall sheet thickness: 50 μm

Comparative example 7

Polyimide film: product with thickness of 12 mu m and tensile elastic modulus of 5.8GPa

Overall sheet thickness: 50 μm

Comparative example 8

Polyimide film: 25 mu m thick product with tensile elastic modulus of 3.4GPa

Overall sheet thickness: 50 μm

Comparative example 9

Polyimide film: 25 mu m thick product with tensile elastic modulus of 3.4GPa

Overall sheet thickness: 75 μm

Comparative example 10

Polyimide film: 25 mu m thick product with tensile elastic modulus of 5.8GPa

Overall sheet thickness: 75 μm

Comparative example 11

Polyimide film: 25 mu m thick product with tensile elastic modulus of 3.4GPa

Overall sheet thickness: 150 μm

Comparative example 12

Polyimide film: 38 mu m thick product with tensile elastic modulus of 3.4GPa

Overall sheet thickness: 150 μm

Comparative example 13

Polyimide film: 75 μm thick product with tensile elastic modulus of 5.8GPa

Overall sheet thickness: 150 μm

Comparative example 14

Polyimide film: 25 μm thick, 5.8GPa tensile modulus of elasticity (same as in example 9)

Overall sheet thickness: 450 μm

[ evaluation method ]

The following test machine was used to evaluate the heat-resistant thermal conductive composite sheet.

Testing machine A: a hot press evaluation tester manufactured by Kawasaki engineering (Ltd.). The shape of the pressure-bonded part of the steel heating tool for pressing used was 10mm × 30 mm.

And a testing machine B: a main pressure bonding apparatus CBM-16 manufactured by Kabushiki Kaisha was manufactured. The shape of the pressure-bonding part of the steel heating tool for pressing used was 1mm × 40 mm.

The set temperature, the crimping time, the pressure applied to the crimping portion, and the number of crimps were set for each test.

(curling of sheet)

When the molded composite sheet was cut to a 300mm square and placed on a horizontal surface in a natural state with the heat-resistant resin film layer on the bottom and the silicone rubber layer on the top, without pressing the sheet or sizing the back, a difference between the sheet end portion, which is caused by the sheet warping upward, and the horizontal surface was 10mm or less, was determined as ": no curl ". Further, a case where the sheet itself is rolled up in a roll shape with the silicone rubber layer inside is described as "x", and a case where the sheet is not rolled up at all but the difference from the horizontal plane exceeds 10mm due to the upward warp of the sheet is described as "Δ".

(thermal conductivity)

As a sheet for thermocompression bonding, it was judged whether or not heat transfer was possible with good efficiency. The set temperature of the heating tool of the testing machine a was set to 300 ℃, the pressure bonding time was set to 20 seconds, the pressure applied to the pressure-bonded part was set to 3MPa, and the number of times of pressure bonding was set to 1. The temperature transmitted through the sheet pieces cut out to 30mm × 50mm was measured using a sheet thermocouple, and the case where the temperature reached 180 to 220 ℃ after 5 seconds was evaluated as "O", and the case where the temperature was outside the above range was evaluated as "X".

(crimp durability)

It is judged whether or not the composite sheet can be repeatedly used as a sheet for thermocompression bonding. Fig. 5 shows a schematic diagram of the crimping durability test. An anisotropic conductive film (acrylic type ACF21, manufactured by hitachi chemical corporation) was temporarily pressure-bonded to a glass plate having a thickness of 50mm × 50mm × 5mm for a length of 20mm using a temporary pressure bonding apparatus ABM-42 manufactured by bridgeware (strain) manufacture (ACF (anisotropic conductive film) test piece 22). The composite sheet 18 was cut to 200mm × 10mm and fixed to the testing machine B so that the heat-resistant resin film (polyimide) side became the heating tool side. The set temperature of the heating tool 23 of the test machine B was set to 350 ℃, the pressure bonding time was set to 10 seconds, and the pressure applied to the pressure-bonded part was set to 4 MPa. The ACF test piece 22 is set on the stage of the testing machine B in such a manner that the heating tool 23 directly contacts the ACF21 through the composite sheet. The ACF test piece 22 itself is replaced every time 1 pressure bonding is performed, but the composite sheet 18 is repeatedly pressure bonded until a sheet component adheres to the ACF21 of the ACF test piece 22 or the composite sheet 18 itself is broken (fig. 5 and 6). The number of times of press-bonding was rated as "good" when it was 50 times or more, and rated as "x" when it was less than 50 times.

The results are shown in the following table. The case judged to be suitable for the present invention is denoted as OK, and the case judged to be unsuitable is denoted as NG.

[ TABLE 1]

[ TABLE 2]

[ TABLE 3]

[ TABLE 4]

Claims

1. A thermal conductive composite sheet for thermocompression bonding, which is a thermal conductive composite sheet for thermocompression bonding, wherein a silicone rubber layer composed of a cured product of a silicone rubber composition is laminated on one surface of a heat-resistant resin film having a glass transition temperature of 200 ℃ or more or a melting point of 300 ℃ or more, the thickness of the whole sheet of the composite sheet is 100 to 400 [ mu ] m, the thickness ratio represented by the silicone rubber layer/the heat-resistant resin film is 2 to 10, the thickness of the heat-resistant resin film is 20 to 50 [ mu ] m, the tensile elastic modulus of the heat-resistant resin film based on the ASTM D-882 measurement method is 4 to 20GPa, the temperature of a heating tool of a thermocompression evaluation tester is set to 300 ℃ in terms of the thermal conductivity of the composite sheet, the pressure bonding time is 20 seconds, the pressure applied to a pressure bonding part is 3MPa, the number of pressure bonding is 1, and the composite sheet is cut into sheet pieces of 30mm x 50mm, measuring the temperature transmitted through the sheet by using a sheet thermocouple, reaching the range of 180-220 ℃ after 5 seconds,

in the hot press evaluation test machine, the shape of the pressure-bonded part of the steel heating tool for pressing was 10mm × 30 mm.

2. The thermally conductive composite sheet for thermocompression bonding according to claim 1, wherein the silicone rubber layer is a cured product of a silicone rubber composition containing:

R¹ _aSiO_(4-a)/2 (I)

in the formula, R¹Are identical or different unsubstituted or substituted monovalent hydrocarbon groups, and at least 2 of 1 molecule are aliphatic unsaturated groups, a is a positive number of 1.95 to 2.05,

3. The thermocompression bonding thermal conductive composite sheet according to claim 1 or 2, wherein the heat-resistant resin film is composed of at least 1 selected from the group consisting of aromatic polyimide, polyamide, polyamideimide, polyethersulfone, polyetherimide, polyethylene naphthalate, polytetrafluoroethylene, and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and a surface of the heat-resistant resin film is surface-treated by physical treatment or chemical treatment.

4. A method for producing the thermocompression bonding thermal conductive composite sheet according to any one of claims 1 to 3, which is a method for producing a thermal conductive composite sheet for thermocompression bonding in which a silicone rubber layer composed of a cured product of a silicone rubber composition is laminated on one surface of a heat-resistant resin film, comprising: a step of laminating the silicone rubber composition molded into a sheet shape directly on a heat-resistant resin film by using a twin-roll or calender roll molding machine to integrate the silicone rubber composition into a composite sheet; and a step of heating and curing the integrated composite sheet at 100 to 160 ℃ without applying tension from the outside.

5. A method for producing the thermocompression bonding thermal conductive composite sheet according to any one of claims 1 to 3, which is a method for producing a thermal conductive composite sheet for thermocompression bonding in which a silicone rubber layer composed of a cured product of a silicone rubber composition is laminated on one surface of a heat-resistant resin film, comprising: a step of applying a diluted solution of the silicone rubber composition diluted with a solvent onto a heat-resistant resin film so that the thickness of the film when the solvent has evaporated is 50 to 380 [ mu ] m; and a step of heating and curing the coated product at 100 to 160 ℃ without applying tension from the outside.

6. The method for producing a thermally conductive composite sheet for thermocompression bonding according to claim 5, wherein 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 taken as 100 parts by mass, and the viscosity of the dilution liquid is 3 to 50 Pa-s at 25 ℃.