KR20030074349A - Silicone Rubber Sheet for Heat-Resistant, Thermal-Conductive Thermocompression - Google Patents

Abstract

The present invention provides a silicone rubber sheet for heat-conductive thermocompression bonding, which can be used at a high temperature of 300 ° C. or more, formed by molding and curing a silicone rubber composition into a sheet, and having good thermal conductivity and excellent durability.

The silicone rubber composition has (A) 100 parts by weight of organopolysiloxane having an average degree of polymerization of 200 or more, (B) 10 to 100 parts by weight of carbon black having a volatile content excluding 0.5% by weight and a BET specific surface area of 100 m ² / g or more. And (C) a curing agent.

Description

Silicon Rubber Sheet for Heat-Resistant, Thermal-Conductive Thermocompression

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat resistant thermally conductive silicone rubber sheet for the purpose of simultaneously applying heat and uniformly applying pressure, and in particular, a laminate having a low strength drop upon heating and which can be repeatedly used at a high temperature of 300 ° C. or higher. The present invention relates to a silicone rubber sheet for heat-resistant thermal conductive thermocompression excellent in durability suitable for a sheet used for forming a flexible printed circuit board or an anisotropic conductive film for use in electrode connection such as a liquid crystal display.

As a thermally conductive electrical insulating material, silicon rubber is blended with a sheet containing powder such as beryllium oxide, aluminum oxide, aluminum hydroxide, magnesium oxide or zinc oxide (see Japanese Patent Laid-Open No. 47-32400) or boron nitride is mixed with silicone rubber. Sheets reinforced with a mesh-type insulating material (see Japanese Utility Model Publication No. 54-184074) and the like are conventionally known, and are already used for thermal insulation of heat-generating components such as power transistors, thyristors, rectifiers, transformers, or power MOS FETs. It is used. However, when such a material is used under high temperature conditions of 200 ° C or higher, there is a drawback that the silicone rubber is degraded by the influence of impurities in the thermal conductivity imparting agent or pH.

On the other hand, for cushioning when thermally compressing an anisotropic conductive film used for connecting a sheet for forming a laminated plate, a flexible printed circuit board, etc. with a press molding machine, or a flexible printed circuit board on which an electrode terminal portion of a liquid crystal display and a drive circuit are mounted. The thermally conductive electrical insulating sheet described above is used as the sheet. For example, Japanese Patent Application Laid-open No. Hei 5-198344 combines boron nitride with silicone rubber and reinforces it with glass cross. Japanese Patent Application Laid-open No. Hei 6-36853 contains boron nitride and conductive material in silicone rubber. The sheet which reinforced with the glass cross and provided antistatic property is disclosed. However, in all such cases, there was a drawback that the silicone rubber deteriorated under high temperature conditions. Nevertheless, especially in recent years, the material of flexible printed circuit boards and anisotropic conductive films has been changed to high-temperature molding type, and the molding temperature is increased to shorten the compression cycle and improve productivity, so that the heat resistance and thermal conductivity are more improved. Development of rubber sheets has been required.

On the other hand, Japanese Patent Laid-Open No. 7-11010 discloses heat resistance and good thermal conductivity that can be used at a temperature of 300 ° C or higher by using 20 to 150 parts by weight of carbon black having 0.5% by weight or less of volatile matter except water as a heat conductivity imparting agent. A heat resistant thermally conductive silicone rubber sheet having However, in this case, since there is a lack of strength under high temperature, there is a drawback that there is a risk of being destroyed by continuous use.

In addition, JP-A-8-174765 discloses a heat-resistant heat conductive silicone rubber composite sheet in which the carbon black compounded silicone rubber composition and the heat resistant resin film are laminated. In this case, although improved from the viewpoint of strength and releasability, since the heat resistant resin film is used, the flexibility of the sheet may be suppressed and the pressure at the time of crimping may be uneven. There was a drawback that there is a possibility that it cannot be used repeatedly because it is easily deformed by heat.

Therefore, the inventors of the present invention have studied diligently to obtain a silicone rubber sheet for heat-heat-conductive thermocompression bonding that can be used at a high temperature of 300 ° C or higher and has good thermal conductivity and excellent durability. When the silicone rubber composition containing 10 to 100 parts by weight of carbon black having a volatile content of 0.5% by weight or less and a BET specific surface area of 10 m ² / g or more is cured into a sheet form, a good result can be obtained. Reached.

It is therefore an object of the present invention to provide a silicone rubber sheet for heat-conductive thermocompression bonding that can be used at a high temperature of 300 ° C. or higher and has excellent thermal conductivity and excellent durability.

The above object of the present invention is a silicone rubber sheet for heat-conductive heat-conductive thermocompression molding by molding and curing a silicone rubber composition into a sheet, wherein the silicone rubber composition (A) 100 parts by weight of organopolysiloxane having an average degree of polymerization of 200 or more, ( B) 10 to 100 parts by weight of carbon black having a volatile content excluding moisture of not more than 0.5% by weight and a BET specific surface area of 100 m ² / g or more, and (C) a curing agent for heat-resistant heat conductive thermocompression bonding. Achieved by a silicone rubber sheet.

<Embodiment of the Invention>

In general, the heat resistance of silicone rubber depends on the compounding composition, and is influenced by the type of base polymer, vinyl group content, type of heat-resistant additive, type of filler, and the like. In addition, due to the influence of pH, moisture or impurities in the composition, it is necessary to pay careful attention to the selection of the additive. Moreover, although carbon black can be used as a filler which improves heat resistance, it is necessary to consider impurities and volatile matter in carbon black. In particular, when carbon black is added in a large amount in order to improve thermal conductivity, the volatilization becomes an important point.

Volatiles of carbon black correspond to the weight of oxygen compounds (acidic components such as carboxyl, quinone, lactone, hydroxyl, etc.) chemically adsorbed on the surface, but the heat resistance of silicone rubber because the oxygen compounds vaporize on the surface by heating. Adversely affects. Therefore, by using the carbon black whose volatile matter is 0.5 weight% or less, the heat resistance which can be used even at high temperature of 300 degreeC or more can be implement | achieved.

In addition, the strength of the silicone rubber is greatly improved by incorporating the reinforcing silica, but the strength is greatly reduced at high temperatures. This is considered to be because the bond between the hydroxyl group and the siloxane polymer on the silica surface is weak to heat. Therefore, in the present invention, by using carbon black having a BET specific surface area of 10 m ² / g or more, the decrease in strength at high temperature is suppressed small, and the durability as a thermocompression silicone rubber sheet is improved.

In addition, by blending carbon black with silicone rubber, the silicone rubber sheet becomes conductive, so that static electricity generated during the pressing process can be removed, thereby preventing the attachment of garbage, dust, and the like and destruction of electronic components mounted on the circuit. You can prevent it.

The organopolysiloxane with an average degree of polymerization of 200 or more, which is the component (A) used in the present invention, is represented by the following average composition formula (1).

R _n SiO _{(4-n) / 2}

(n is a positive number from 1.95 to 2.05)

However, in the formula, R represents a substituted or unsubstituted monovalent hydrocarbon group, and specifically, alkyl groups such as methyl group, ethyl group and propyl group, cycloalkyl groups such as cyclopentyl group and cyclohexyl group, alkenyl groups such as vinyl group and allyl group Aryl groups, such as a phenyl group and a tolyl group, or the halogenated hydrocarbon group in which these hydrogen atoms were partially substituted by the chlorine atom, a fluorine atom, etc. are illustrated. In the present invention, it is generally preferable that the main chain of the organopolysiloxane consists of dimethylsiloxane units or that a vinyl group, a phenyl group, a trifluoropropyl group, or the like is introduced into the main chain of the organopolysiloxane. Moreover, what is necessary is just to block the molecular chain terminal of a triorganosilyl group or a hydroxyl group, and this triorgano silyl group is illustrated with a trimethylsilyl group, a dimethyl vinyl silyl group, a trivinyl silyl group, etc. Moreover, it is preferable that the polymerization degree of this component is 200 or more and the viscosity in 25 degreeC is 300 cs or more. If the degree of polymerization is less than or equal to 200, the mechanical strength after curing decreases and becomes weak.

Next, at the same time as component (B) is, the volatile components other than water being 0.5% by weight or less at the time of a BET specific surface area of 10O m ² / g or more carbon blacks improve the heat resistance of the silicone rubber sheet Sikkim and at the same time the mechanical strength, in particular heating It improves strength and gives antistatic property by conduction. Carbon black is classified into furnace black, channel black, thermal black, acetylene black and the like by the production method thereof. As carbon black having a volatile content of 0.5% by weight or less, acetylene black having a specific surface area is suitable. The measuring method of volatile matter is described in the "carbon black test method for rubber | gum" of JISK6221. Specifically, a prescribed amount of carbon black is placed in the crucible, and the volatilization loss after heating at 950 ° C. for 7 minutes is measured.

It is preferable to use the compounding quantity of this (B) component in 10-100 weight part, especially 20-80 weight part with respect to 100 weight part of (A) component. If it is 10 parts by weight or less, thermal conductivity and mechanical strength are insufficient, and if it is 100 parts by weight or more, the compounding becomes difficult and the molding processability is very poor.

The hardening | curing agent which is (C) component can be suitably selected from the conventionally well-known thing normally used for hardening of a silicone rubber, and can be used. As such a hardening | curing agent, For example, organic peroxides, such as di-t- butyl peroxide used for radical reaction, 2, 5- dimethyl- 2, 5- di (t- butyl peroxy) hexane, dicumyl peroxide; When organopolysiloxane of (A) component has an alkenyl group as an addition reaction hardening | curing agent, what consists of organohydrogenpolysiloxane containing 2 or more of hydrogen atoms couple | bonded with the silicon atom in 1 molecule, and a platinum group metal type catalyst; When the organopolysiloxane of (A) component contains a silanol group as a condensation reaction hardening | curing agent, the organosilicon compound etc. which have two or more hydrolysable groups, such as an alkoxy group, an acetoxy group, a ketooxime group, a propenoxy group, etc. are illustrated. . The addition amount of these hardening | curing agents can be made similarly to the case of normal silicone rubber.

In this invention, heat resistance can be improved by adding a cerium oxide powder to this silicone rubber composition. The addition amount of the said cerium oxide is the range of 0.1-5 weight part with respect to 100 weight part of (A) component, On the contrary, if it exceeds 5 weight part, heat resistance will fall. As the cerium oxide powder, one having a relatively large specific surface area having a BET specific surface area of 50 m ² / g or more is preferably used.

In this invention, in order to make thermal conductivity favorable, it is preferable to add other thermal conductive fillers other than the carbon black of the said (B) component. As such a thermally conductive filler, inorganic powders, such as aluminum oxide, boron nitride, aluminum nitride, aluminum hydroxide, magnesium oxide, zinc oxide, and quartz, or metal powders, such as silver, nickel, copper, iron, etc. are suitable. It is preferable that the compounding quantity of such a heat transfer filler is 50-2,000 weight part with respect to 100 weight part of organopolysiloxane, and it is especially preferable to use in the range of 100-1,600 weight part. If it is 50 parts by weight or less, the thermal conductivity becomes insufficient, and if it exceeds 2,000 parts by weight, the moldability deteriorates, the mechanical strength after curing becomes low, and the flexibility of the rubber is lost. In addition, the thermal conductivity of the silicone rubber composition is preferably 0.5 W / mK or more from the viewpoint of efficiently transferring heat as the heat transfer medium.

In the present invention, in the silicone rubber composition, in addition, reinforcing silica fillers such as hydrophilic silica and hydrophobic silica, fillers such as cray, calcium carbonate, diatomaceous earth, titanium dioxide, dispersants such as low molecular siloxane ester and silanol, silane Adhesion imparting agents, such as a coupling agent and a titanium coupling agent, the platinum group metal type catalyst which gives a flame retardance, tetrafluoro polyethylene particle which raises the green strength of a rubber compound, etc. can be added.

In the blending of the silicone rubber composition of the present invention, the above components may be kneaded using a mixer such as a twin-screw roll, kneader, Benbury mixer, planetary mixer, etc., but generally, only the curing agent is added immediately before use. desirable. Moreover, as a shaping | molding method of the silicone rubber sheet of this invention, the silicone rubber composition which mix | blended the hardening | curing agent is blown out by the calender or the extruder to predetermined thickness, and it hardens | cures, and it melt | dissolves in liquid silicone rubber composition or solvents, such as toluene, and liquidizes it. The method of hardening | curing after coating a silicone rubber composition on a film is mentioned. The thickness of the silicone rubber sheet thus formed is preferably in the range of 0.1 to 10 mm. If the thickness is 0.1 mm or less, the pressure is not uniformly applied to the adherend, so the pressure is easily applied unevenly, and when the thickness is 10 mm or more, heat transfer is deteriorated.

Since the silicone rubber sheet of the present invention is excellent in heat resistance, thermal conductivity, strength and workability and has elasticity as silicone rubber, the purpose of simultaneously applying heat and uniformly applying pressure when forming a laminate and a flexible printed circuit board using a press molding machine. It is effective as a sheet used for thermally compressing an anisotropic conductive film (ACF) used for connecting the electrode terminal portion of the liquid crystal panel or PDP panel and the electrode terminal portion of the FPC substrate on which the driving LSI is mounted. .

<Example>

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

<Example 1>

To 100 parts by weight of methylvinylpolysiloxane having an average degree of polymerization of 8,000 containing 99.85 mol% of dimethylsiloxane units and 0.15 mol% of methylvinylsiloxane units as the component (A), the average particle diameter as the component (B) was 23 nm, volatile matter 0.10 wt%, 50 parts by weight of acetylene black having a BET specific surface area of 130 m ² / g was blended with a biaxial roll, kneaded and homogenized. 0.1 weight part of vinylsiloxane complex (platinum content 1 weight%) of a chloroplatinic acid, 0.05 weight part of ethynyl cyclohexanol which is a control agent of a platinum catalyst, and methylhydrogen polysiloxane represented by following General formula (2) with respect to 100 weight part of this silicone rubber compositions. 1.5 weight part was added, it knead | mixed well by the biaxial roll, and the curable silicone rubber composition was adjusted.

The obtained silicone rubber composition was ejected to a thickness of 0.25 mm using a calender molding machine, then transferred onto a 100 µm thick polyethylene terephthalate (PET) film, and passed through the inside at 5 ° C. for 5 minutes to cure the silicone rubber composition. . Next, the PET film was peeled off and heat-treated at 20 ° C. for 4 hours in a dryer to prepare a heat resistant heat conductive silicone rubber sheet having a thickness of 0.25 mm.

<Example 2>

A heat resistant thermally conductive silicone rubber sheet having a thickness of 0.25 mm was prepared in the same manner as in Example 1 except that 0.5 parts by weight of the cerium oxide powder having a BET specific surface area of 140 m ² / g was added to the silicone rubber composition of Example 1.

<Example 3>

As the component (A), 80 parts by weight of methylvinylpolysiloxane having an average degree of polymerization of 8,000 consisting of 99.85 mol% of dimethylsiloxane units and 0.15 mol% of methylvinylsiloxane units, an average of 99.5 mol% of dimethylsiloxane units and 0.5 mol% of methylvinylsiloxane units On the base consisting of 20 parts by weight of methylvinylpolysiloxane having a degree of polymerization of 8,000, (B) as an ingredient, an average particle diameter of 23 nm, a volatile matter of 10% by weight, 20 parts by weight of acetylene black having a BET specific surface area of 130 m ² / g, and an average of a thermally conductive filler 250 parts by weight of aluminum oxide powder having a particle diameter of 2.5 mu m and 0.5 parts by weight of cerium oxide powder having a BET specific surface area of 140 m ² / g were blended with a pressurized kneader, kneaded and homogenized. 0.05 parts by weight of a vinylsiloxane complex of platinum chloride (platinum content 1% by weight), 0.025 parts by weight of ethynylcyclohexanol as a control agent of the platinum catalyst, and methylhydrogenpolysiloxane represented by the formula (2) based on 100 parts by weight of the silicone rubber composition. After adding 0.7 parts by weight and mixing, in the same manner as in Example 1, a heat resistant thermally conductive silicone rubber sheet having a thickness of 0.25 mm was prepared.

<Example 4>

A heat resistant thermally conductive silicone rubber sheet having a thickness of 0.25 mm was manufactured in the same manner as in Example 3, except that 150 parts by weight of aluminum powder having an average particle diameter of 15 μm was used as the thermal conductive filler.

Comparative Example 1

A silicone rubber sheet having a thickness of 0.25 mm in the same manner as in Example 1, except that 50 parts by weight of an acetylene black having an average particle diameter of 35 nm, a volatile matter of 10% by weight, and a BET specific surface area of 69 m ² / g was used as the component (B). Was prepared.

Comparative Example 2

A silicone rubber sheet having a thickness of 0.25 mm was prepared in the same manner as in Example 1, except that 50 parts by weight of a furnace particle having an average particle diameter of 50 nm, a volatile matter of 0.6% by weight, and a BET specific surface area of 50 m ² / g was used as the component (B). .

Comparative Example 3

42 parts by weight of reinforcing silica Aerosil 200 (trade name manufactured by Nippon Aelozyl Co., Ltd.) in 100 parts by weight of methylvinylpolysiloxane having an average degree of polymerization of about 8,000 consisting of 99.85 mol% of dimethylsiloxane units and 0.15 mol% of methylvinylsiloxane units. And 4 parts by weight of α, ω-dihydroxydimethylpolysiloxane represented by the following formula (3) as a dispersant, kneading with a kneader, and using a silicone rubber composition heat-treated at 170 ° C. for 1 hour in the same manner as in Example 1 0.25 mm rubber sheets were made.

The initial properties and the properties at 200 ° C. of the sheets prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were measured. The results are shown in Table 1.

Teflon (registered trademark of DuPont Co., Ltd.) with a thickness of 30 µm on an anisotropic conductive film having a thickness of 22 µm on two flexible printed circuit boards provided with a copper electrode having a pitch of 25 µm (to adjust the position of the upper and lower copper electrodes). The film was placed thereon, the sheets prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were placed thereon, installed in a pressing machine, and the pressing tool heated at 400 ° C. at the sheet side for 6 seconds at a pressure of 40 kgf / cm ² . Squeezed. This pressing was repeated, and the number of times until the anisotropic conductive film could not be heat cured at a uniform pressure was measured. This number of times was confirmed by conduction of the copper electrode of the upper and lower flexible printed circuit boards. The results are shown in Table 2.

The heat resistant thermally conductive thermocompression-bonding silicone rubber sheet of the present invention can be used at a high temperature of 300 ° C. or higher, and has excellent thermal conductivity and excellent durability.

Claims (8)

A silicone rubber sheet for heat-resistant thermal conductive thermocompression molding by molding and curing a silicone rubber composition into a sheet form, wherein the silicone rubber composition comprises (A) 100 parts by weight of organopolysiloxane having an average degree of polymerization of 200 or more, and (B) volatiles except water 10 to 100 parts by weight of carbon black having a BET specific surface area of at most 0.5% by weight and at least 100 m ² / g, and (C) a curing agent. The silicone rubber sheet according to claim 1, wherein the silicone rubber composition contains 0.1 to 5 parts by weight of cerium oxide powder. The silicone rubber sheet according to claim 1, wherein the silicone rubber composition further contains 50 to 2,000 parts by weight of the thermally conductive filler. 4. The silicone rubber sheet for thermally conductive thermal compression according to claim 3, wherein the thermally conductive filler is at least one powder selected from thermally conductive inorganic powders or metal powders. The silicone rubber sheet according to claim 4, wherein the inorganic powder is at least one inorganic powder selected from aluminum oxide, aluminum hydroxide, zinc oxide, crystalline silica, and boron nitride. The silicone rubber sheet according to claim 4 or 5, wherein the metal powder is at least one metal powder selected from aluminum, silver, copper and nickel. The heat resistant thermally conductive silicone rubber sheet according to any one of claims 1 to 5, wherein the silicone rubber composition has a thermal conductivity of 0.5 W / mK or more. The silicone rubber sheet according to any one of claims 1 to 5, wherein the sheet has a thickness in the range of 0.1 to 10 mm.