JP3041213B2 - Heat resistant heat conductive silicone rubber composite sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermocompression bonding sheet used for transmitting heat and applying pressure uniformly, and more particularly, to a heat resistant sheet which has excellent strength and releasability and can be used at a high temperature. The present invention relates to a conductive silicone rubber composite sheet.

[0002]

2. Description of the Related Art Conventionally, beryllium oxide,
Powders such as aluminum oxide, aluminum hydroxide, magnesium oxide, and zinc oxide may be blended (see JP-A-47-3).
No. 2400), and boron nitride was blended with silicone rubber and reinforced with a stitch-shaped insulating material (Japanese Utility Model Application Laid-Open No. 54-18 / 1979).
A heat conductive electric insulating material and the like are known, and are used as a heat radiation insulating material for heat-generating components such as a power transistor, a thyristor, a rectifier, a transformer, and a power MOSFET. However, when these materials are used under a high temperature condition of 200 ° C. or higher, there is a disadvantage that the silicone rubber is deteriorated due to the influence of impurities and pH in the thermal conductivity imparting agent.

On the other hand, an anisotropic conductive film used for connecting a sheet for forming a laminated board and a flexible printed board by a press forming machine, and a flexible printed board on which a drive circuit is mounted and an electrode terminal of a liquid crystal display. The above-mentioned heat conductive electric insulating sheet is used as a sheet when thermocompression bonding is performed by a compression machine. For example, Japanese Unexamined Patent Publication No.
Japanese Patent Application Laid-Open No. 368/368 discloses a silicone rubber compounded with boron nitride and reinforced with glass cloth.
No. 53 discloses a silicone rubber in which boron nitride and a conductive substance are blended and reinforced with a glass cloth to impart an antistatic property. However, under high temperature conditions, the silicone rubber also deteriorates. There are drawbacks. In particular, recently, the materials of flexible printed circuit boards and anisotropic conductive films have been changed to high-temperature molding types, and molding temperatures have been increasing in order to further shorten the pressing cycle and improve productivity. Thermal conductivity has become important.

[0004] In response to such a demand, the present inventor can use carbon black having a volatile content of 0.5% or less excluding water as a thermal conductivity-imparting agent so that it can be used at 300 ° C or more. A silicone rubber sheet having excellent heat resistance and good thermal conductivity was proposed (Japanese Patent Application No. 6-1843).
No. 64). However, although this silicone rubber sheet is excellent in heat resistance, since it is a single silicone rubber, its mechanical strength is insufficient for some applications, and there is a possibility that the silicone rubber sheet will break when used continuously. In addition, due to the adhesiveness of the silicone rubber, there is a disadvantage that the workability is deteriorated because the sheet is easily stuck to the pressing tool or the object to be pressed after the pressing.

[0005]

The inventors of the present invention have conducted intensive studies to improve the strength and workability of the silicone rubber, and as a result, have found that the silicone rubber and the heat-resistant resin film can be combined. The inventors have found that good results can be obtained, and have reached the present invention. Accordingly, an object of the present invention is to provide a silicone rubber composite sheet having good thermal conductivity and excellent heat resistance, strength and workability.

[0006]

SUMMARY OF THE INVENTION The above objects of the present invention are as follows.
(A) an organopolysiloxane having an average degree of polymerization of 200 or more; 100 parts by weight, (B) a volatile matter excluding water of 0.5
A heat-resistant and heat-conductive silicone rubber composite sheet obtained by curing, on a heat-resistant resin film, a silicone rubber composition comprising carbon black of not more than 20% by weight; More achieved.

The component (A) used in the present invention has an average compositional formula of R _n SiO _{(4-n) / 2} (n is a positive number from 1.95 to 2.05).
Is an organopolysiloxane having an average degree of polymerization of 200 or more. R in the formula is a substituted or unsubstituted monovalent hydrocarbon group, specifically, an alkyl group such as a methyl group, an ethyl group and a propyl group, a cycloalkyl group such as a cyclopentyl group and a cyclohexyl group, a vinyl group, Alkenyl group such as allyl group, phenyl group, aryl group such as tolyl group,
Or a halogenated hydrocarbon group in which a hydrogen atom of these groups is partially substituted with a chlorine atom, a fluorine atom, or the like, but generally, the main chain of the organopolysiloxane is a dimethylsiloxane unit. Or those obtained by introducing a vinyl group, a phenyl group, a trifluoropropyl group, or the like into the main chain of the organopolysiloxane.

The terminal of the molecular chain is blocked with a triorganosilyl group or a hydroxyl group. Examples of the triorganosilyl group in this case include a trimethylsilyl group and a dimethylvinylsilyl group. Moreover, it is preferable that 0.001-5 mol%, especially 0.01-0.5 mol% is an alkenyl group from a curability and physical characteristics. The average degree of polymerization of this component is required to be 200 or more,
Is preferably 300 cs or more.
If the average degree of polymerization is 200 or less, the mechanical strength after curing is inferior and the composition becomes brittle.

Next, carbon black having a volatile content of 0.5% by weight or less excluding the water component (B) improves the heat resistance and mechanical strength of the silicone rubber sheet and makes it conductive. This imparts antistatic properties. The carbon black is classified into furnace black, channel black, thermal black, acetylene black and the like according to the production method. In the present invention, particularly, acetylene black and a conductive black disclosed in JP-A-1-272667 are disclosed. Carbon black and the like are preferred.

The method for measuring the volatile content described above is based on JIS K
It is defined by 6221 “Testing method for carbon black for rubber”. Specifically, a specified amount of carbon black is put in a crucible, and the volatilization loss after heating at 950 ° C. for 7 minutes is measured. The amount of the component (B) is as follows:
It is preferably in the range of 20 to 150 parts by weight, particularly preferably in the range of 40 to 100 parts by weight, based on 100 parts by weight of the component. When the amount of the component (B) is less than 20 parts by weight, the thermal conductivity becomes insufficient. On the other hand, when the amount exceeds 150 parts by weight, the compounding becomes difficult and the moldability becomes extremely poor.

The curing agent (C) can be appropriately selected from known curing agents usually used for curing silicone rubber. For example, in the case of organic peroxide vulcanization, organic peroxides such as di-t-butyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, dicumyl peroxide, etc. It is preferable that the distribution amount is 0.1 to 5 parts by weight based on 100 parts by weight of the organopolysiloxane (A).

[0012] The organopolysiloxane of the component (A) is
When the compound has two or more alkenyl groups bonded to a silicon atom, two hydrogen atoms bonded to the silicon atom are contained in one molecule.
An addition reaction curing agent comprising an organohydrogenpolysiloxane and a platinum group metal-based catalyst containing at least one component is included. The compounding amount of the organohydrogenpolysiloxane is based on the amount of the silicon atom bonded to the alkenyl group of the component (A). The ratio of hydrogen atoms (≡SiH / ≡Si-alkenyl) is preferably from 0.5 to 5, and the platinum-based metal catalyst is preferably from 1 to 1000 ppm based on the component (A).

When the organopolysiloxane (A) contains a silanol group, condensation of an organosilicon compound having two or more hydrolyzable groups such as an alkoxy group, an acetoxy group, a ketoxime group, a propenoxy group, etc. Reaction hardeners are exemplified. In the present invention, it is preferable to use an organic peroxide or an addition reaction curing agent from the viewpoint of ease of molding. The addition amount of these curing agents may be the same as the addition amount to ordinary silicone rubber, but it is particularly necessary to select one that does not adversely affect heat resistance.

In the present invention, heat resistance can be improved by further adding cerium oxide powder to the above silicone rubber composition. The amount of the cerium oxide powder to be added is 0.1 to 100 parts by weight of the component (A).
It is preferred to be within the range of 5 parts by weight. If it exceeds 5 parts by weight, the heat resistance is rather reduced. The cerium oxide powder preferably has a BET specific surface area of 50 m ² / g or more.

In the present invention, the silicone rubber composition may further contain, if necessary, reinforcing silica fillers such as hydrophilic silica and hydrophobic silica, clay, calcium carbonate, diatomaceous earth, titanium dioxide and the like. Fillers, dispersants such as low molecular weight siloxane esters, silanols, etc., adhesives such as silane coupling agents and titanium coupling agents, platinum group metal compounds which impart flame retardancy, polytetras which increase the green strength of rubber compounds Fluoroethylene particles can also be added.

In order to compound such a silicone rubber composition, the above components may be kneaded using a mixer such as a two-roller, a kneader, a Banbury mixer, and a planetarium mixer. Is preferably added. The heat resistance of silicone rubber varies depending on the composition, and is affected by the type of base polymer, vinyl group content, type of heat-resistance imparting additive, type of filler, and the like. In addition, it is affected by the pH, the amount of water or the amount of impurities in the composition. Therefore, great care must be taken in selecting additives.

In the present invention, it is necessary to consider impurities and volatile components in carbon black used as a filler for improving heat resistance. In particular, when a large amount of carbon black is added to improve thermal conductivity, its volatile content is important. Volatile content of carbon black is determined by oxygen compounds (carboxyl,
Oxygen components such as quinone, lactone and hydroxyl).

This causes vaporization from the surface when heated, which adversely affects the heat resistance of the silicone rubber. Therefore, it is an essential condition in the present invention to use carbon black having a volatile content of 5% by weight or less. The thermal conductivity of the silicone rubber used in the present invention is 0.8 × 10 ^−3.
cal / cm · sec · ° C. or more, especially 1.0 × 10 ⁻³ c
It is preferably at least al / cm · sec · ° C.

The heat-resistant resin film used in the present invention comprises:
Since it is used even at a temperature of around 300 ° C., it is necessary to have excellent mechanical strength and releasability at a high temperature. Specifically, an aromatic polyimide having a glass transition point of 200 ° C. or higher,
Polyamide imide, aromatic polyamide, polyether sulfone, a resin film such as polyether imide,
Aromatic polyamide films and aromatic polyimide films are preferred. Specific examples of the aromatic polyimide film include Kapton (trade name of Toray DuPont), Apical (trade name of Kanebuchi Chemical Industry Co., Ltd.), Upilex (trade name of Ube Industries, Ltd.), aromatic Specific examples of the polyamide film include Aramica (trade name, manufactured by Asahi Kasei Kogyo Co., Ltd.).

The fluororesin film has a melting point of 30.
It is also preferable to use one at 0 ° C. or higher. As such a film, polytetrafluoroethylene (PTF)
E) or a film such as a tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PFA). Commercially available products of these films include Teflon (trade name, manufactured by Dupont Japan Limited) and Nitoflon (trade name, manufactured by Nitto Denko Corporation). Among these, it is preferable to use a type reinforced with a glass cloth from the viewpoint of strength.

Further, in order to improve the performance of the composite sheet of the present invention, a heat-resistant resin film provided with electrical conductivity by blending carbon black, or a thermally conductive powder such as aluminum oxide or magnesium oxide is blended. It is preferable to use a heat-resistant resin film provided with thermal conductivity. Kapton MT can be mentioned as a commercial product of the heat-resistant resin film provided with thermal conductivity.

The thickness of the heat-resistant resin film is 5 to 300
μm, particularly preferably 10 to 100 μm. When the thickness is less than 5 μm, the mechanical strength of the film itself is insufficient, so that the film may be cut at the time of forming the sheet or during use as a pressure-bonded sheet. 3
When the thickness exceeds 00 μm, the heat transmission becomes poor and the thermocompression bonding may be insufficient.

The method for producing the composite sheet of the present invention includes:
A silicone composition containing up to a curing agent is dispensed to a predetermined thickness by a calender or extruder, then bonded to a heat-resistant resin film, cured, and dissolved in a liquid silicone rubber composition or a solvent such as toluene. And a method of coating the surface of the heat-resistant resin film with the liquefied silicone rubber composition and then curing.

In order to improve the adhesion between the silicone rubber composition and the heat-resistant resin film, a primer is previously applied to the surface of the heat-resistant resin film, or a silane coupling agent is added to the silicone rubber composition. It is preferable to add an adhesion imparting agent such as When a fluororesin film is used, it is preferable that the film surface is subjected to an etching treatment with a sodium-naphthalene solution or the like to impart adhesiveness before coating or the like.

The thickness of the silicone rubber composite sheet formed as described above is preferably 0.1 to 10 mm. If the thickness is less than 0.1 mm, it is not possible to sufficiently follow the object to be pressed, and if it exceeds 10 mm, the heat transfer may be poor. The heat-resistant resin film may be provided on one side or both sides of the silicone rubber layer depending on the intended use of the obtained silicone rubber composite sheet.

The composite sheet of the present invention is excellent in heat resistance, heat conductivity, strength and workability and has elasticity as silicone rubber. Therefore, when forming a laminate or a flexible printed board with a press molding machine, It is effective as a sheet used for the purpose of transmitting heat and applying pressure uniformly, or a sheet used for thermocompression bonding of an anisotropic conductive film used for connection between an electrode terminal portion of a liquid crystal display and a substrate by a compression machine.

[0027]

As described above, the heat-resistant and heat-conductive silicone rubber sheet of the present invention has an improved strength because it is compounded with a heat-resistant resin film, and has a life enough to withstand continuous use. In addition, since the pressing tool and the object to be compressed do not directly contact the silicone rubber surface, the sheet does not stick after the compression and the workability is improved. Furthermore, since the silicone rubber is made conductive by blending carbon black, it is possible to remove static electricity generated during the pressure bonding process and to prevent adhesion of dust and dust. Therefore, it is possible to prevent the electronic components mounted on the circuit from being destroyed.

[0028]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

Embodiment 1 The component (A) is composed of 99.85 mol% of dimethylsiloxane units, 0.125 mol% of methylvinylsiloxane units and 0.025 mol% of dimethylvinylsiloxane units, and has an average weight of 800.
Using 100 parts by weight of methylvinylpolysiloxane of
As a component (B), 50 parts by weight of acetylene black having an average particle diameter of 40 nm and a volatile content of 0.10% by weight were added, and a reinforcing silica (Aerosil R-972 (Aerosil R-972)) was further added.
silR-972): 5 parts by weight of Degussa (trade name, manufactured by Degussa) were added with a two-roll mill, and the mixture was kneaded and homogenized.

With respect to 100 parts by weight of the obtained silicone rubber compound, 0.1 part by weight of an isopropyl alcohol solution of chloroplatinic acid (amount of platinum: 2% by weight) (component C) and 3-methyl-1 which is an acetylenic alcohol 0.05 parts by weight of butyn-3-ol and 1.2 parts by weight (component C) of methylhydrogenpolysiloxane represented by the following formula 1 were added and kneaded well to prepare a curable composition.

Embedded image Next, an aromatic polyimide film having a thickness of 12 μm (Kapton: having a glass transition point of 35
(0 ° C. or higher), primer C (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) was applied to the surface, and dried at room temperature for 30 minutes.

The previously prepared silicone rubber curable composition was fractionated using a calendering machine so as to have a thickness of 0.3 mm, and then transferred onto a 100 μm-thick PET film. After the prepared Kapton film to which the primer was applied was pressed, the curable composition was cured by passing through a heating furnace at 160 ° C. for 5 minutes. Next, after peeling off the PET film, the film was dried at 200 ° C.
For 4 hours to produce a heat- and heat-conductive silicone rubber composite sheet.

Embodiment 2 FIG. A heat-resistant and heat-conductive silicone rubber composite sheet was produced in exactly the same manner as in Example 1, except that an aromatic polyamide film having a thickness of 12 μm (Aramica: no glass transition point) was used as the heat-resistant resin film.

Embodiment 3 FIG. As a heat-resistant resin film, one side was treated with a sodium-naphthalene solution and had a thickness of 75
A heat-resistant and heat-conductive silicone rubber composite sheet was produced in exactly the same manner as in Example 1 except that a PTFE film (nitoflon, melting point: 327 ° C.) reinforced with a glass cloth of μm was used.

Embodiment 4 FIG. (A) 70 parts by weight of a methylvinylpolysiloxane having an average degree of polymerization of 8000, comprising 99.85 mol% of dimethylsiloxane units, 0.125 mol% of methylvinylsiloxane units and 0.025 mol% of dimethylvinylsiloxane units, as a component; And an average degree of polymerization of 99.5 mol% of dimethylsiloxane units, 0.475 mol% of methylvinylsiloxane units and 0.025 mol% of dimethylvinylsiloxane units.
A mixture consisting of 30 parts by weight of methylvinylpolysiloxane 0, 50 parts by weight of acetylene black having an average particle diameter of 53 nm and a volatile matter of 0.15% by weight was added thereto as a component (B). The specific surface area is 140m ² /
g of cerium oxide powder (0.5 parts by weight) was added and mixed with a two-roll mill, and the mixture was kneaded and homogenized.

To 100 parts by weight of the obtained silicone compound, in the same manner as in Example 1, component C (curing agent)
After adding and mixing, the thickness of the primer
A heat-resistant and heat-conductive silicone rubber composite sheet was prepared by laminating a μm Kapton film.

Example 5 Instead of the PET film used in Example 1, a PTFE film (Nitoflon) reinforced with a glass cloth having a thickness of 75 μm and having one side bonded was used, and a silicone rubber was formed on the bonding surface. Except that the curable composition was transferred, a heat-resistant thermally conductive silicone rubber composite sheet attached to a double-sided film was produced in exactly the same manner as in Example 1.

Embodiment 6 FIG. (A) 50 parts by weight of methylvinylpolysiloxane having an average degree of polymerization of 8000, comprising 99.85 mol% of dimethylsiloxane units, 0.125 mol% of methylvinylsiloxane units, and 0.025 mol% of dimethylvinylsiloxane units; And an average degree of polymerization of 99.5 mol% of dimethylsiloxane units, 0.475 mol% of methylvinylsiloxane units and 0.025 mol% of dimethylvinylsiloxane units.
A mixture consisting of 50 parts by weight of methylvinylpolysiloxane of No. 0 was added as a component (B), and 65 parts by weight of acetylene black having an average particle diameter of 40 nm and a volatile matter of 0.10% by weight were further added. The specific surface area is 140m ² /
g of cerium oxide powder (0.5 parts by weight) was added and mixed with a two-roll mill, and the mixture was kneaded and homogenized.

To 100 parts by weight of the obtained silicone compound, the component C (curing agent) used in Example 1 and 0.5 part by weight of γ-glycidoxypropyltrimethoxysilane (adhesion-imparting agent) were added and mixed. Then, a heat-resistant thermally conductive silicone rubber composite sheet was produced in the same manner as in Example 1, except that a conductive Kapton film containing carbon black having a thickness of 30 μm was used.

Comparative Example 1 The curable silicone rubber composition prepared in the same manner as in Example 1 was processed using a calendering machine to produce a sheet of a single silicone rubber having a thickness of 0.3 mm.

Comparative Example 2 A heat-resistant and heat-conductive silicone rubber composite sheet was prepared in exactly the same manner as in Example 1 except that as the component (B), 50% by weight of furnace black having an average particle size of 30 nm and a volatile content of 0.7% by weight was used. Produced.

Comparative Example 3 A heat-resistant and heat-conductive silicone rubber composite sheet was prepared in exactly the same manner as in Example 2 except that 50% by weight of furnace black having an average particle size of 30 nm and a volatile content of 1.5% by weight was used as the component (B). Produced.

Comparative Example 4 The thickness used in Example 1 was 1
Example 1 except that a 30 μm thick polyphenylene sulfide film (glass transition point 90 ° C.) was used instead of the 2 μm aromatic polyimide film (Kapton).
A heat conductive silicone rubber composite sheet was produced in exactly the same manner as in the above case.

With the film side of the sheets prepared in Examples 1 to 6 and Comparative Examples 1 to 4 facing upward, a Teflon film having a thickness of 30 μm was provided under the sheet, and then copper electrodes were provided at a pitch of 25 μm. Align the upper and lower copper electrodes with the two flexible printed circuit boards, place a 22 μm-thick anisotropic conductive film between them, and then install it on the crimping machine.
Using a pressure tool heated to 340 ° C, 40 kgf /
The film was pressed from the film side at a pressure of cm ² for 20 seconds.

By repeating this pressing operation, the state of close contact of the sheet with the pressing tool was observed, and the number of times until the anisotropic conductive film could no longer be heated and cured at a uniform pressure was measured. These results are as shown in Table 1. The number of times that the anisotropic conductive film could not be cured by heating under a uniform pressure was confirmed by the fact that the copper electrodes of the upper and lower flexible printed circuit boards did not conduct. In the case of Example 5, the measurement was performed with the Kapton film side facing the pressing tool side and without placing a Teflon film. The pressurizing time was extended to 30 seconds in Examples 3 and 5.

[0045]

[Table 1]

From the above results, in the case of Example 5, the workability is particularly good because there is no need to place a Teflon film below. In the case of Comparative Example 1, it was found that the sheet had to be peeled off because the sheet was stuck to the pressing tool every time the sheet was pressed, and that the workability was poor. The results of measuring the thermal conductivity of the cured silicone rubber and the silicone rubber composition containing no carbon used in each test are as follows. Examples 1, 2, ^3, 5: 1.6 × 10 ⁻³ (cal / c
Comparative Example 1, 4: 1.6 × 10 ^-3 Example 4: 1.4 × 10 ^-3 Example 6: 2.0 × 10 ^-3 Comparative Example 2: 1.5 × 10 ^-3 Comparative Example 3: 1.4 × 10 ^-3 KE-951U: 5.9 × 10 ^-4 (commercial product not containing carbon black and manufactured by Shin-Etsu Chemical Co., Ltd.)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-111010 (JP, A) JP-A-4-74645 (JP, A) JP-A-6-316690 (JP, A) JP-A-58-58 218711 (JP, A) JP-A-6-155517 (JP, A) Japanese Utility Model Application Showa 49-101078 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00-35 / 00

Claims (8)

(57) [Claims] 1. An organopolysiloxane having an average degree of polymerization of 200 or more; 100 parts by weight; (B) a carbon black having a volatile content of 0.5% by weight or less excluding water;
A heat-resistant thermally conductive silicone rubber composite sheet obtained by curing a silicone rubber composition comprising 0 to 150 parts by weight and a curing agent (C) on a heat-resistant resin film. 2. The heat-resistant and heat-conductive silicone rubber composite sheet according to claim 1, wherein the heat-resistant resin film is a resin film having a glass transition point of 200 ° C. or higher. 3. The heat-resistant resin film has a melting point of 300 ° C.
The heat-resistant and heat-conductive silicone rubber composite sheet according to claim 1, which is the above fluororesin film. 4. The heat- and heat-conductive silicone rubber composite sheet according to claim 1, wherein the silicone rubber composition contains 0.1 to 5 parts by weight of cerium oxide powder. 5. The heat-resistant resin film has a thickness of 5 to 300.
The heat-resistant and heat-conductive silicone rubber composite sheet according to any one of claims 1 to 4, which has a range of μm. 6. The heat- and heat-conductive silicone rubber composite sheet according to claim 1, wherein the total thickness of the silicone rubber layer and the heat-resistant resin film is 0.1 to 10 mm. 7. The heat-resistant and heat-conductive silicone rubber composite sheet according to claim 1, wherein the heat-resistant resin film contains a heat-conductive powder. 8. The heat-resistant and heat-conductive silicone rubber composite sheet according to claim 1, wherein the heat-resistant resin film contains carbon black.