JP2003261769A - Thermocompression bonding silicone rubber sheet with heat resistance and thermal conductivity - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermocompression bonding silicone rubber sheet with heat resistance and thermal conductivity, capable of being used at such a high temperature as 300°C or higher, having the good thermal conductivity, and excellent in durability. <P>SOLUTION: This thermocompression bonding silicone rubber sheet with the heat resistance and thermal conductivity is given by forming a silicone rubber composition into a sheet and curing the formed sheet. The silicone rubber composition comprises (A) an organopolysiloxane having an average degree of polymerization of ≥200 in an amount of 100 pts.wt., (B) carbon black having a volatile content of ≤0.5 wt.% which excludes water content and having a BET specific surface area of ≥100 m<SP>2</SP>/g in an amount of 10-100 pts.wt., and (C) a hardening agent. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant and heat-conductive silicone rubber sheet for thermocompression bonding, which is used for the purpose of transmitting heat and applying a uniform pressure. Suitable for sheets that can be used repeatedly at high temperatures for forming laminated plates and flexible printed boards, or thermocompression-bonding sheets for anisotropic conductive films that are used for connecting electrodes such as liquid crystal displays. The present invention relates to a heat resistant and heat conductive silicone rubber sheet for thermocompression bonding.

[0002]

2. Description of the Related Art A sheet (see Japanese Patent Laid-Open No. 47-32400) in which powder of beryllium oxide, aluminum oxide, aluminum hydroxide, magnesium oxide, zinc oxide or the like is mixed with silicone rubber as a heat conductive electric insulating material, Sheets of silicone rubber compounded with boron nitride and reinforced with a mesh-like insulating material (see Japanese Utility Model Publication No. 54-184074) have been conventionally known, and have already been known as power transistors, thyristors, rectifiers, transformers, or power sources. MOS FE
Used for heat insulation of heat-generating components such as T. However, when such a material is used under a high temperature condition of 200 ° C. or higher, there is a drawback that the silicone rubber deteriorates due to the influence of impurities in the thermal conductivity imparting agent and the pH.

On the other hand, a sheet for forming a laminated plate, a flexible printed circuit board, etc. by a press molding machine, and an anisotropic conductive film used for connecting the electrode terminal part of the liquid crystal display and the flexible printed circuit board on which the drive circuit is mounted. The above-mentioned thermally conductive electrically insulating sheet is used as a cushioning sheet for thermocompression bonding with a pressure bonding machine. For example, Japanese Patent Laid-Open No. 5-1
In Japanese Patent No. 98344, a silicone rubber compounded with boron nitride and reinforced with glass cloth is disclosed in Japanese Patent Laid-Open No. 6-36.
Japanese Patent Publication No. 853 discloses a sheet in which boron nitride and a conductive substance are mixed in silicone rubber and reinforced with glass cloth to impart antistatic properties. However, in each of these cases, there is a drawback that the silicone rubber deteriorates under high temperature conditions. Nevertheless, especially recently, the materials for flexible printed circuit boards and anisotropic conductive films are changing to high-temperature molding types, and the molding temperature has risen in order to further shorten the pressure bonding cycle and improve productivity. Therefore, it has been desired to develop a heat conductive rubber sheet having improved heat resistance and heat conductivity.

On the other hand, in Japanese Patent Application Laid-Open No. 7-11010, the volatile component excluding water as a thermal conductivity imparting agent is 0.
By using 20 to 150 parts by weight of carbon black in an amount of 5% by weight or less, a heat-resistant and heat-conductive silicone rubber sheet having heat resistance usable at a temperature of 300 ° C. or higher and good thermal conductivity has been proposed. However, in this case, since the strength at high temperature is insufficient, there is a drawback that it may be broken by continuous use.

Further, Japanese Patent Application Laid-Open No. 8-174765 discloses a heat and heat conductive silicone rubber composite sheet in which the above carbon black-blended silicone rubber composition and a heat resistant resin film are laminated. In this case, although the strength and the releasability are improved, the flexibility of the sheet is suppressed because the heat-resistant resin film is used, and the pressure at the time of pressure bonding may be non-uniform. Top, 300
At a high temperature of ℃ or more, even the above-mentioned heat-resistant resin film is easily deformed by heat, so there is a drawback that it may not be able to be used repeatedly.

[0006]

Therefore, the present inventors
As a result of diligent study to obtain a heat-resistant and heat-conductive silicone rubber sheet for thermocompression bonding, which can be used at a high temperature of 300 ° C. or more and has excellent heat conductivity and excellent durability, water was removed as a heat conductivity imparting agent. Further, when a 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 100 m ² / g or more is cured into a sheet, good results are obtained. They have found that the results can be obtained and have reached the present invention. Accordingly, an object of the present invention is to provide a heat-resistant and heat-conductive silicone rubber sheet for thermocompression bonding, which can be used at a high temperature of 300 ° C. or higher and has good thermal conductivity and excellent durability. It is in.

[0007]

The above objects of the present invention are as follows.
A heat- and heat-conductive silicone rubber sheet for thermocompression bonding, obtained by molding and curing a silicone rubber composition into a sheet, wherein the silicone rubber composition is (A) an organopolysiloxane having an average degree of polymerization of 200 or more: 100 parts by weight, (B) volatile matter excluding water content of 0.5% by weight or less and BET specific surface area of 100 m ² / g or more: 10 to 100 parts by weight, and (C) curing agent It is achieved by a heat-resistant and heat-conductive silicone rubber sheet for thermocompression bonding.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Generally, the heat resistance of silicone rubber differs depending 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. Further, since it is affected by pH, water content or impurities in the composition, it is necessary to pay sufficient attention to selection of additives. Although carbon black can be used as a filler for improving heat resistance, it is necessary to consider impurities and volatile components in carbon black. In particular, when a large amount of carbon black is added to improve the thermal conductivity, the volatile content thereof is an important point.

The volatile content of carbon black corresponds to the weight of oxygen compounds (acidic components such as carboxyl, quinone, lactone and hydroxyl) that are chemically adsorbed on the surface. Since it vaporizes, it adversely affects the heat resistance of the silicone rubber.
Therefore, by using carbon black having a volatile content of 0.5% by weight or less, it is possible to realize heat resistance that can be used even at a high temperature of 300 ° C. or higher.

Further, the strength of the silicone rubber is significantly improved by blending the reinforcing silica, but the strength is greatly reduced at high temperature. It is considered that this is because the bond between the hydroxyl group on the silica surface and the siloxane polymer is weak to heat. Therefore, in the present invention, the BET specific surface area is 10
By using 0 m ² / g or more of carbon black, the decrease in strength at high temperature is suppressed to a small extent, and the durability as a thermocompression-bonded silicone rubber sheet is improved. Furthermore, by blending the silicone rubber with carbon black, the silicone rubber sheet becomes electrically conductive, which makes it possible to eliminate static electricity generated during the crimping process. It is possible to prevent the destruction of existing electronic components.

The organopolysiloxane having 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 ···· (1) (n is 1.
However, R in the formula represents a substituted or unsubstituted monovalent hydrocarbon group, specifically, an alkyl group such as a methyl group, an ethyl group and a propyl group, a cyclopentyl group, a cyclohexyl group. Group such as cycloalkyl group, vinyl group, alkenyl group such as allyl group, aryl group such as phenyl group and tolyl group, or halogenated hydrocarbon group in which hydrogen atom thereof is partially substituted with chlorine atom, fluorine atom, etc. Etc. are illustrated. In the present invention, it is generally preferable that the main chain of the organopolysiloxane is composed of dimethylsiloxane units, or that the main chain of this organopolysiloxane has a vinyl group, a phenyl group, a trifluoropropyl group or the like introduced therein. The end of the molecular chain may be blocked with a triorganosilyl group or a hydroxyl group, and examples of the triorganosilyl group include a trimethylsilyl group, a dimethylvinylsilyl group and a trivinylsilyl group.
The degree of polymerization of this component is preferably 200 or more, and the viscosity at 25 ° C. is preferably 300 cs or more. When the degree of polymerization is 200 or less, the mechanical strength after curing is poor and the composition becomes brittle.

Next, the volatile component excluding water, which is the component (B), is 0.5% by weight or less, and the BET specific surface area is 1
The carbon black of 00 m ² / g or more improves the heat resistance of the silicone rubber sheet, improves the mechanical strength, especially the strength when heated, and further imparts the antistatic property due to the conductivity. Carbon black is classified into furnace black, channel black, thermal black, acetylene black and the like depending on the manufacturing method. As the carbon black having a volatile content of 0.5% by weight or less, acetylene black having a developed specific surface area is suitable. The method for measuring volatile components is described in JIS K 6221 "Testing method for carbon black for rubber". Specifically, a specified amount of carbon black is put in a crucible, and after heating at 950 ° C. for 7 minutes, the volatilization loss is measured. The blending amount of the component (B) is preferably 10 to 100 parts by weight, more preferably 20 to 80 parts by weight based on 100 parts by weight of the component (A). If it is less than 10 parts by weight, thermal conductivity and mechanical strength will be insufficient, and 100
If the amount is more than parts by weight, the compounding becomes difficult and the moldability becomes extremely poor.

The curing agent which is the component (C) can be appropriately selected and used from conventionally known ones which are usually used for curing silicone rubber. As such a curing agent, for example, di-
t-Butyl peroxide, 2,5-dimethyl-2,5
-Organic peroxides such as di (t-butylperoxy) hexane and dicumyl peroxide; hydrogen bonded to a silicon atom when the organopolysiloxane of component (A) as an addition reaction curing agent has an alkenyl group A compound comprising an organohydrogenpolysiloxane having two or more atoms in one molecule and a platinum group metal-based catalyst; when the organopolysiloxane of the component (A) as a condensation reaction curing agent contains a silanol group, Examples thereof include organosilicon compounds having two or more hydrolyzable groups such as alkoxy groups, acetoxy groups, ketoxime groups and propenoxy groups. The addition amount of these curing agents may be the same as in the case of ordinary silicone rubber.

In the present invention, heat resistance can be improved by adding cerium oxide powder to this silicone rubber composition. The addition amount of the cerium oxide is in the range of 0.1 to 5 parts by weight with respect to 100 parts by weight of the component (A), and when it exceeds 5 parts by weight, the heat resistance is decreased. Further, as the cerium oxide powder, BE
It is preferable to use one having a relatively large specific surface area of T specific surface area of 50 m ² / g or more.

In the present invention, in order to improve the thermal conductivity, it is preferable to add other thermally conductive fillers in addition to the carbon black as the component (B).
Such heat conductive fillers include inorganic powders such as aluminum oxide, boron nitride, aluminum nitride, aluminum hydroxide, magnesium oxide, zinc oxide, and quartz.
Alternatively, a metal powder of silver, nickel, copper, iron or the like is suitable. The blending amount of these heat-transmitting fillers is preferably 50 to 2,000 parts by weight, and particularly preferably 100 to 1,600 parts by weight, based on 100 parts by weight of the organopolysiloxane. If it is less than 50 parts by weight, the thermal conductivity will be insufficient, and if it exceeds 2,000 parts by weight, the moldability will be poor and the mechanical strength after curing will be low and the flexibility of the rubber will be lost. Further, the thermal conductivity of the silicone rubber composition is preferably 0.5 W / mK or more from the viewpoint of efficiently transmitting heat as a heat transfer medium.

In the present invention, in addition, a reinforcing silica filler such as hydrophilic silica or hydrophobic silica, clay, calcium carbonate, and
Diatomaceous earth, fillers such as titanium dioxide, low molecular weight siloxane esters, dispersants such as silanol, silane coupling agents, adhesion promoters such as titanium coupling agents, platinum group metal catalysts that impart flame retardancy, rubber Tetrafluoropolyethylene particles which increase the green strength of the compound may be added.

The composition of the silicone rubber composition of the present invention is
The above components may be kneaded using a mixer such as a two-roll mill, a kneader, a Banbury mixer, a planetary mixer or the like, but it is generally preferable to add the curing agent just before using it. Further, as a method for molding the silicone rubber sheet of the present invention, a silicone rubber composition containing a curing agent is dispensed to a predetermined thickness with a calendar or an extruder and then cured, a liquid silicone rubber composition or Examples include a method in which a film is coated with a liquefied silicone rubber composition dissolved in a solvent such as toluene and then cured. The silicone rubber sheet molded in this way has a thickness of 0.1 to 1
It is preferably in the range of 0 mm. If the thickness is 0.1 mm or less, the pressure-bonded body cannot be sufficiently followed, so that the pressure is apt to be unevenly distributed, and if the thickness is 10 mm or more, the heat transfer is deteriorated.

The silicone rubber sheet of the present invention is excellent in heat resistance, thermal conductivity, strength and workability, and has elasticity as a silicone rubber.
A sheet used for the purpose of transmitting heat and evenly applying pressure when molding a flexible printed circuit board,
As a sheet for thermocompression bonding of an anisotropic conductive film (ACF) used for connecting an electrode terminal of a liquid crystal panel or a PDP panel and an electrode terminal of an FPC board on which a driving LSI is mounted with a thermocompression bonding machine It is valid.

[0019]

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Example 1. Dimethylsiloxane unit 9 as component (A)
9.85 mol%, methyl vinyl siloxane unit 0.15
100 parts by weight of methylvinylpolysiloxane having an average degree of polymerization of 8,000 consisting of mol%, acetylene black 50 having an average particle size of 23 nm as the component (B), a volatile content of 0.10% by weight, and a BET specific surface area of 130 m ² / g. Parts by weight were blended with a two-roll mill and kneaded to homogenize. With respect to 100 parts by weight of this silicone rubber composition, 0.1 part by weight of a vinylsiloxane complex of chloroplatinic acid (platinum content 1% by weight), 0.05 part by weight of ethynylcyclohexanol which is a platinum catalyst control agent and the following ( 2) Expression Methyl hydrogen polysiloxane represented by 1.5
A part by weight was added and kneaded well with a two-roll to prepare a curable silicone rubber composition. The thickness of the obtained silicone rubber composition is 0.25 m using a calender molding machine.
Then, it was transferred to a polyethylene terephthalate (PET) film having a thickness of 100 μm and passed through a heating furnace at 160 ° C. for 5 minutes to cure the silicone rubber composition. Next, the PET film is peeled off and dried in a dryer for 200
It heat-processed at 4 degreeC for 4 hours, and produced the heat resistant heat conductive silicone rubber sheet of thickness 0.25mm.

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

Example 3. As the component (A), 80 parts by weight of methylvinylpolysiloxane having an average degree of polymerization of 8,000, which is composed of 99.85 mol% of dimethylsiloxane units and 0.15 mol% of methylvinylsiloxane units, and 99.5 mol% of dimethylsiloxane units, Based on 20 parts by weight of methyl vinyl polysiloxane having an average degree of polymerization of 8,000 and containing 0.5 mol% of methyl vinyl siloxane unit,
As the component (B), the average particle diameter is 23 nm and the volatile content is 0.10.
% By weight, 20 parts by weight of acetylene black having a BET specific surface area of 130 m ² / g, and an average particle size of 2.
250 parts by weight of 5 μm aluminum oxide powder and BE
0.5 part by weight of a cerium oxide powder having a T specific surface area of 140 m ² / g was blended with a pressure kneader and kneaded to homogenize.
Vinylsiloxane complex of chloroplatinic acid (platinum content 1% by weight) per 100 parts by weight of this silicone rubber composition
0.05 parts by weight, 0.025 parts by weight of ethynylcyclohexanol, which is a platinum catalyst control agent, and 0.7 parts by weight of methylhydrogenpolysiloxane represented by the above formula (2) are added and mixed. In the same manner as in Example 1, a heat-resistant and heat-conductive silicone rubber sheet having a thickness of 0.25 mm was produced.

Example 4. Example 3 except that 150 parts by weight of aluminum powder having an average particle size of 15 μm was used instead of the aluminum oxide powder as the heat conductive filler.
A heat resistant and heat conductive silicone rubber sheet having a thickness of 0.25 mm was prepared in the same manner as in.

Comparative Example 1. As the component (B), the average particle size is 35 nm, the volatile content is 0.10% by weight, and the BET specific surface area is 69.
A 0.25 mm-thick silicone rubber sheet was produced in the same manner as in Example 1 except that 50 parts by weight of m ² / g acetylene black was used.

Comparative Example 2. As the component (B), the average particle diameter is 50 nm, the volatile content is 0.6% by weight, and the BET specific surface area is 50 m.
^A 0.25 mm thick silicone rubber sheet was prepared in the same manner as in Example 1 except that 50 parts by weight of ² / g of furnace black was used.

Comparative Example 3. Dimethylsiloxane unit 99.
100 parts by weight of methylvinylpolysiloxane having an average degree of polymerization of about 8,000 consisting of 85 mol% and methylvinylsiloxane unit 0.15 mol% was added to the reinforcing silica Ae.
42 parts by weight of Rosil 200 (trade name of Nippon Aerosil Co., Ltd.) and 4 parts by weight of α, ω-dihydroxydimethylpolysiloxane represented by the following formula (3) as a dispersant were kneaded with a kneader, and the mixture was kneaded at 170 ° C. for 1 hour. A silicone rubber sheet having a thickness of 0.25 mm was produced in the same manner as in Example 1 using the silicone rubber composition that had been heat treated for a period of time.

The initial characteristics and the characteristics 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.

[Table 1]

A Teflon film having a thickness of 30 μm is placed on an anisotropic conductive film having a thickness of 22 μm sandwiched between two flexible printed boards provided with copper electrodes having a pitch of 25 μm (the upper and lower copper electrodes are aligned). A film (registered trademark of DuPont Co., Ltd.) is placed, and the sheets prepared in Examples 1 to 4 and Comparative Examples 1 to 3 are placed on the film, then placed in a pressure bonding machine, and heated to 400 ° C. from the sheet side. 40 tools
It was pressure-bonded for 6 seconds at a pressure of kgf / cm ² . This pressure bonding was repeated, and the number of times until the anisotropic conductive film could not be heat-cured with a uniform pressure was measured. This number was confirmed by the conduction of copper electrodes on the upper and lower flexible printed boards. The results are shown in Table 2.

[0028]

[Table 2]

Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08K 5/541 C08K 5/541 F term (reference) 4F071 AA67 AB03 AB07 AB08 AB09 AB18 AB26 AB27 AC08 AC16 AE02 AE17 AF44 AH12 BB04 BB06 BC01 4J002 CP031 CP042 CP081 CP141 DA036 DA079 DA089 DA117 DE079 DE098 DE109 DE149 DF019 DJ019 DK009 EK037 EX037 FD018 FD019 FD147

Claims (8)

[Claims] 1. A heat- and heat-conductive silicone rubber sheet for thermocompression bonding, which is obtained by molding and curing a silicone rubber composition into a sheet, wherein the silicone rubber composition comprises (A).
Organopolysiloxane having an average degree of polymerization of 200 or more: 100 parts by weight, (B) volatile matter excluding water is 0.5
% Or less and BET specific surface area of 100 m ² / g
The above-mentioned carbon black: 10 to 100 parts by weight, and (C) a curing agent, a silicone rubber sheet for heat and heat conductive thermocompression bonding. 2. The heat resistant and heat conductive silicone rubber sheet for thermocompression bonding according to claim 1, wherein the silicone rubber composition contains 0.1 to 5 parts by weight of cerium oxide powder. 3. The silicone rubber composition further contains 50 to 2,000 parts by weight of a thermally conductive filler.
Alternatively, the heat-resistant and heat-conductive silicone rubber sheet for thermocompression bonding described in 2. 4. The heat-resistant and heat-conductive silicone rubber for thermocompression bonding according to claim 3, wherein the heat-conductive filler is at least one kind of powder selected from heat-conductive inorganic powder or metal powder. Sheet. 5. The heat resistance 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. Silicone rubber sheet for thermal conductive thermocompression bonding. 6. The metal powder is aluminum, silver,
The heat-resistant and heat-conductive silicone rubber sheet for thermocompression bonding according to claim 4 or 5, which is at least one metal powder selected from copper and nickel. 7. The heat-resistant and heat-conductive silicone rubber sheet for thermocompression bonding according to claim 1, wherein the silicone rubber composition has a thermal conductivity of 0.5 W / mK or more. 8. The heat-resistant and heat-conductive silicone rubber sheet for thermocompression bonding according to claim 1, wherein the thickness of the sheet is in the range of 0.1 to 10 mm.