KR20100044710A - Silicone rubber sheet for thermocompression bonding - Google Patents

Abstract

PURPOSE: A silicone rubber sheet for thermocompression bonding is provided to ensure excellent thermocompression durability, low elongation in cutting, and excellent durability to mechanical breakage. CONSTITUTION: A silicone rubber sheet(5) for thermocompression bonding is obtained by molding and curing a silicone rubber composition in a sheet shape and has elongation of 50-120 % in cutting at 23 °C, hardness of 65-75 measured with a type A durometer at 23 °C, and thermal conductivity of 0.5-1.0 W/mK. The silicone rubber sheet comprises (A) 100.0 parts by mass of organopolysiloxane with an average polymerization degree of 3000 or more, (B) 50-250 parts by mass of at least one thermoconductive powder selected from metal, metal oxide, metal nitride and metal carbide, (C) 5-60 parts by mass of carbon black powder, (D) 0-40 parts by mass of reinforcing silica micropowder with a BET non-surface area of 50 m^2/g or more, and (E) a hardener.

Description

Thermocompression Silicone Rubber Sheet {SILICONE RUBBER SHEET FOR THERMOCOMPRESSION BONDING}

The present invention relates to a silicone rubber sheet for thermocompression bonding used for the purpose of uniformly applying pressure to a to-be-adhered object while having thermal conductivity, and particularly has good heat resistance, and is permanently deformed even after repeated pressing at 300 占 폚 or higher. Heat deterioration is small, durability is excellent against mechanical breakdown, the elongation at the time of cutting is not only small appropriately, it has the appropriate hardness and the suitable thermal conductivity, and the heat used for crimping the anisotropic conductive film used for the connection of electrodes, such as a liquid crystal display, The present invention relates to a silicone rubber sheet for pressing and a thermocompression silicone rubber sheet capable of high-precision pressing, which can be adapted to molding a laminate or a flexible printed circuit board.

Background Art In recent years, liquid crystal panels, plasma display panels, and organic EL panels have been widely used as displays for mobile phones, portable computers, computer monitors, video cameras, digital cameras, navigation systems, and thin televisions. In recent years, electronic paper has become popular as a rewritable medium. However, in these display panels, in order to drive an image, a lead electrode on the panel side and a lead electrode of a flexible printed circuit board on which a driving LSI is mounted are formed using an anisotropic conductive adhesive. Thermocompression bonding and electrical and mechanical connection are performed.

In recent years, as the technology of high-definition display advances, especially in the case of liquid crystal panels, narrowing of the lead electrode is required. However, in the connection process between lead electrodes using an anisotropic conductive adhesive, in addition to the dimensional tolerances at the time of forming each lead electrode, the alignment error of the lead electrodes, the difference in the thermal expansion rate between the flexible printed circuit board and the panel, and the compression Since the position shift of lead electrodes, etc. generate | occur | produce, narrow-pitch connection was not easy.

As the silicone rubber sheet for thermocompression bonding, for example, boron nitride is blended with silicone rubber and reinforced with glass fiber (Patent Document 1). It is known to reinforce and to give antistatic property (patent document 2), to mix | blend positive heat conductive materials, such as a ceramic and a metal, with silicone rubber (patent document 3). However, these silicone rubber sheets for thermocompression bonding have not been basically optimized in heat resistance, cushioning properties, etc., and therefore, when these silicone rubber sheets were used for narrow pitch connection, good results could not be obtained.

[Patent Document 1] Japanese Patent Application Laid-Open No. 5-198344

[Patent Document 2] Japanese Unexamined Patent Publication No. 6-36853

[Patent Document 3] Japanese Unexamined Patent Publication No. 6-289352

Further, the heat resistance is further improved by blending carbon black having a volatile matter content of 0.5% or less excluding moisture to silicone rubber (Patent Document 4), or by blending carbon black having a BET specific surface area of 100 m 2 / g or more. One thermocompression silicone rubber sheet (Patent Document 5) is known. However, although this silicone rubber sheet for thermocompression bonding is very excellent in heat resistance and durability, there existed a drawback that elongation, hardness, thermal conductivity, etc. at the time of cutting | disconnection to the sheet | seat corresponding to narrow pitch connection were not optimized. Thus, the silicone rubber sheet for thermocompression which is excellent in heat resistance and durability which can cope with narrowing of a lead electrode is not obtained yet.

[Patent Document 4] Japanese Unexamined Patent Publication No. 7-11010

[Patent Document 5] Japanese Unexamined Patent Publication No. 2003-261769

Therefore, the present inventors earnestly examined the thermocompression-bonding silicone rubber sheet which is not only excellent in heat resistance and durability, but also can cope with narrowing of the lead electrode. As a result, three characteristics of (1) hardness at room temperature, (2) elongation at break, and (3) thermal conductivity of the silicone rubber sheet are very important in order to cope with narrowing of the lead electrode and thermal conductivity. It is preferable to use metal silicon powder and / or crystalline silicon dioxide powder as the powder, and when these powders are used, it is possible to reduce the compression permanent distortion of the silicone rubber sheet, so that deterioration due to permanent deformation based on repeated pressing It has turned out that it becomes easy to make it small. Moreover, since both powders are low specific gravity, specific gravity of a sheet can also be made light, and the handleability of a silicone rubber sheet also becomes favorable.

Moreover, as silicone which mix | blended metal silicon powder, thermally conductive organopolysiloxane composition (patent document 6) formed by co-charging aluminum nitride and metal silicon powder, and thermally conductive silicone which mix | blended metal silicon with silicone rubber as a thermally conductive filler. A composition and a molded article thereof (Patent Document 7), a metal silicon powder having an average particle diameter of 100 µm or less, and a high thermal conductivity silicone rubber composition (Patent Document 8) having both high thermal conductivity and low compression set permanent distortion, and having an average particle diameter of 100 µm or less Although the silicone rubber composition for the high thermal conductivity passion bonding roll or the fixing belt and the passion bonding roll or the fixing belt (patent document 9) which mix | blended the metal silicon powder are known, these all do not consider the application to the silicone rubber sheet for thermocompression bonding, Optimization of hardness, elongation and thermal conductivity for the application of the silicone rubber sheet for thermal compression Not.

[Patent Document 6] Japanese Unexamined Patent Application Publication No. 3-14873

[Patent Document 7] Japanese Unexamined Patent Publication No. 2000-63670

[Patent Document 8] Japanese Patent Application Laid-Open No. 2007-138100

[Patent Document 9] Japanese Unexamined Patent Publication No. 2007-171946

Moreover, as a silicone sheet which mix | blended the metal silicon powder in consideration of the thermocompression use, the heat transfer elastic sheet (patent document 10) which mix | blended the metal silicon powder as a heat conductive electrical insulation is known. However, since this sheet is not optimized for hardness, elongation and thermal conductivity for thermocompression applications, there is a problem when used as a thermocompression sheet, and in particular, it cannot be used as a sheet for narrow pitch connection.

[Patent Document 10] Japanese Unexamined Patent Publication No. 2007-311628

That is, the 1st objective of this invention is not only excellent in thermocompression durability under the high temperature of 300 degreeC or more, but also high precision thermocompression bonding used when crimping lead electrodes of narrow pitch in a liquid crystal display etc. through anisotropic conductive film. It is an object of the present invention to provide a silicone rubber sheet for thermal compression.

A second object of the present invention is to provide a silicone rubber sheet for thermocompression bonding which can realize high-precision molding, which is suitable as a cushion sheet for use in forming a laminate or flexible printed circuit board.

MEANS TO SOLVE THE PROBLEM As a result of earnestly examining in order to achieve the various objective mentioned above, the present inventors mix | blended a thermally conductive powder, carbon black powder, and a hardening | curing agent with a fixed ratio with respect to what is called a base polymer high solubility organopolysiloxane which is a base polymer. And BET ratio as needed so that the elongation at the time of cutting at 23 degreeC may be 50 to 120%, the hardness at 23 degreeC measured by a type A durometer is 65 to 75, and thermal conductivity will be 0.5 to 1.0 W / mK. When a certain amount of fine powder-reinforced silica having a surface area of 50 m 2 / g or more was blended, and the obtained composition was molded into a sheet form and then cured, it was found that a good result can be obtained and the present invention was reached.

That is, the present invention

(A) organopolysiloxane with an average degree of polymerization of 3000 or more: 100 parts by mass

(B) at least one thermally conductive powder selected from metals, metal oxides, metal nitrides and metal carbides: 50 to 250 parts by mass

(C) carbon black powder: 5 to 60 parts by mass

(D) Reinforcing silica fine powder having a BET specific surface area of 50 m 2 / g or more: an amount of 0 to 40 parts by mass, wherein the total amount of components (C) and (D) is 10 to 60 parts by mass, and

(E) curing agent

It is a silicone rubber sheet formed by molding a silicone rubber composition comprising a sheet into a sheet, and then curing it. The elongation at break at 23 ° C. is 50 to 120%, and the hardness at 23 ° C. measured by a type A durometer is 65. And a heat conductivity of 0.5 to 1.0 W / mK at the same time being from 75 to 75.

In the present invention, the organopolysiloxane having an average degree of polymerization of 3,000 or more as the component (A) is one or more organopolysiloxanes containing an organopolysiloxane having at least two average alkenyl groups in one molecule represented by the following average composition formula 1. 0.10-0.30 mol% of the total R contained in the organopolysiloxane molecule which is comprised from a molecule and is (A) component is a vinyl group, and the total vinyl group amount P (mol%) of the organopolysiloxane molecule of this (A) component While adjusting the usage-amount of the said (A) component and (D) component so that the sum total of the numerical value Q divided by the mass part of the reinforcement silica fine powder of (D) component by 100 may be 0.20 to 0.50, It is preferable that the hardening | curing agent of E) component contains the organohydrogenpolysiloxane which has a hydrogen atom couple | bonded with at least 2 silicon atoms, and a platinum type catalyst.

<Mean Composition 1>

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

However, n in the mean composition formula 1 is a positive number of 1.9-2.4, R represents a substituted or unsubstituted monovalent hydrocarbon group, 0.0001-10 mol% of R which each molecule has is a vinyl group, 80 mol% or more is a methyl group to be.

In this invention, it is preferable that the thermally conductive powder which is (B) component is a metal silicon powder, and it is especially preferable that average particle diameter is 1-20 micrometers. It is preferable that the shape is an irregular form of what is called pulverized powder manufactured by the grinding | pulverization method, or spherical powder manufactured by the spraying method. A forced oxide film may be formed on the surface of the metal silicon powder. Moreover, the case where the thermally conductive powder which is (B) component in this invention is crystalline silicon dioxide powder of 1-20 micrometers of average particle diameters is also a preferable aspect of this invention. Moreover, it is preferable that the thickness of the silicone rubber sheet for thermocompression bonding of this invention is 0.05-1 mm.

The silicone rubber sheet of the present invention is not only excellent in thermocompression durability, but also has a relatively small elongation at cutting, and has an appropriate hardness and an appropriate thermal conductivity, so that lead electrodes of narrow pitch can be used for high-temperature thermocompression bonding through anisotropic conductive films. It is suitable as a silicone rubber sheet for thermocompression bonding. Moreover, when the silicone rubber sheet of this invention is used as a cushion sheet used at the time of shaping a laminated board or a flexible printed circuit board, shaping | molding of high precision becomes possible.

First, the meaning of the terms "average particle diameter" and "average degree of polymerization" used in the present specification will be described.

"Average particle diameter":

About the average particle diameter of carbon black, it is an average particle diameter by what is called electron microscopy which measures a primary particle diameter from the photograph image | photographed using the electron microscope, and carries out an arithmetic mean of the particle size calculated | required. In addition, although carbon black generally has primary particles aggregated to form secondary particles, the average particle size referred to herein refers to the average particle diameter of primary particles, not the average particle diameter of the secondary particles.

The average particle diameter of a thermally conductive powder measures particle size distribution by the optical diffraction / scattering method, and means the particle diameter when the mass integrated value integrated at the particle diameter side becomes 50%. Concrete measurement can be performed, for example by micro track etc. which are the particle size analyzers manufactured by Nikki Corporation.

"Average degree of polymerization":

The mean value of the number of silicon atoms which comprise the siloxane bond which comprises a skeleton in organopolysiloxane etc. is meant.

Next, the composition used for this invention is demonstrated.

[Composition]

The narrow-pitch lead electrodes corresponding to narrowing of the lead electrodes on the panel side due to the high precision of display panels such as liquid crystal panels and the outer lead electrodes of the flexible printed circuit board on which the LSI for driving the image is driven are mounted. In high-precision thermocompression connection by an anisotropic conductive film, it is important to suppress the positional shift of lead electrodes at the time of crimping | compression-bonding.

In order to suppress the positional shift of the lead electrode at the time of the said thermocompression bonding, the thermocompression bonding silicone sheet of this invention has the characteristics of (1)-(3) shown below.

(1) The elongation at the time of cutting | disconnection at the room temperature of 23 degreeC needs to be comparatively small to 50 to 120%, and it is especially preferable that it is 60 to 110%. Basically, the elongation is good in terms of the positional shift of the lead electrode. However, when the elongation is less than 50%, the flexibility of the sheet is insufficient, so that in the case of unevenness or step in the portion to be crimped, the local stress cannot be dispersed, and thus the force in the bending direction is applied to the sheet. In this case, a problem arises that the sheet may break.

(2) It is necessary that the hardness in the room temperature of 23 degreeC measured by the type A durometer is 65-75, and it is especially preferable that it is 67-73. This hardness prevents misalignment of the lead electrodes, and corrects the tolerances of the flatness, flatness, or parallelism of the object to be compressed to achieve a cushioning property for delivering a uniform pressure.

(3) It is necessary that the thermal conductivity in room temperature of 23 degreeC is 0.5-1.0 W / mK, and it is especially preferable that it is 0.6-0.9 W / mK. In order to transfer the heat from the heat tool of the thermocompression bonding apparatus to an anisotropic conductive film, it is preferable that the thermal conductivity is high. However, when the thermal conductivity is larger than 1.0 W / mK, heat is rapidly excessively transferred to the anisotropic conductive film. In this case, the viscosity of the anisotropic conductive film before hardening becomes too low rapidly and flows out between connection electrodes, and the electrical connection of an electrode may become inadequate.

On the other hand, if it is lower than 0.5 W / mK, since heat is hardly transmitted to the anisotropic conductive film, the temperature of the heat tool must be increased. In order to raise the temperature of a heat tool, the burden on a thermocompression bonding apparatus becomes heavy. In addition, since the higher temperature heat tool contacts the thermocompression bonding silicone sheet, thermal degradation of the silicone sheet is promoted. Moreover, a problem may arise because a high temperature heat tool provides radiant heat etc. to the color filter of the liquid crystal panel which is weak to heat.

Next, the (A) component-(E) component which is an essential component in the composition used for this invention is demonstrated.

(A) Ingredient:

 The organopolysiloxane of the average degree of polymerization 3000 or more which is (A) component used by this invention is represented by following average composition formula 1, for example.

<Mean Composition 1>

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

However, in formula (1), n is a positive number of 1.95 to 2.4, and R represents a substituted or unsubstituted monovalent hydrocarbon group.

Specific examples of the substituted or unsubstituted monovalent hydrocarbon group represented by R include 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 and phenyl group And an aryl group such as a tolyl group, or a halogenated hydrocarbon group in which a hydrogen atom of these groups is partially substituted with a halogen atom such as a chlorine atom or a fluorine atom.

As organopolysiloxane of (A) component, it is preferable that a principal chain contains a dimethylsiloxane unit, or introduce | transduced organic groups, such as a methyl group, a vinyl group, a phenyl group, and a trifluoropropyl group, into the principal chain of this organopolysiloxane. . In particular, it is preferable that 0.0001-10 mol% of the said organic group is a vinyl group, and 80 mol% or more is a methyl group. It is also preferable that the molecular chain ends are blocked with triorganosilyl groups or hydroxyl groups. Examples of the triorganosilyl group include trimethylsilyl group, dimethylvinylsilyl group, trivinylsilyl group and the like.

As the organopolysiloxane of the component (A), only one type may be used or a plurality of types may be mixed and used, but from 0.10 to the total R of all the organopolysiloxane molecules of the component (A) represented by the formula (1) It is preferable that 0.30 mol% is a vinyl group. In addition, in this invention, it is necessary for the average polymerization degree of (A) component represented by (1) general formula to be 3000 or more. If the degree of polymerization is less than 3000, the mechanical strength after curing is poor.

(B) Ingredients:

Component (B) is at least one thermally conductive powder selected from metals, metal oxides, metal nitrides and metal carbides, and is a filler that imparts thermal conductivity to the silicone rubber sheet of the present invention. These specific examples include boron nitride and nitride as metal nitrides such as silver, copper, iron, metal silicon, nickel, aluminum, and the like, and metal oxides such as zinc oxide, aluminum oxide, magnesium oxide, silicon dioxide, and iron oxide. Examples of metal carbides such as aluminum and silicon nitride include silicon carbide and boron carbide.

Among the thermally conductive powders described above, metal silicon powder and crystalline silicon dioxide powder are particularly preferable. By using these powders, the compression molding distortion can be made small, and the deterioration due to permanent deformation caused by repeated pressing becomes small, so that the silicone rubber sheet for thermocompression with excellent durability can be realized. Moreover, since both powders are low specific gravity and the specific gravity of a sheet can be made light, the handleability of the silicone rubber sheet for thermocompression bonding becomes favorable.

The shape of these powders may be any one of spherical, elliptic, flat, square irregular, rounded irregular, needle and the like, and is not particularly limited. For example, in the case of metallic silicon, spherical shape, irregularity by grinding | pulverization, etc. can be illustrated.

In addition, the purity of the thermally conductive powder is not particularly limited, but is preferably 50% or more, particularly 80% or more, and more preferably 95% or more from the viewpoint of imparting thermal conductivity. The metal silicon powder having high purity is free from defects in the surface of the natural oxide film and has good high temperature thermal stability, but it is particularly preferable to provide a forced oxide film on the surface of the metal silicon powder. By providing a forced oxide film, it is possible to eliminate the active point on the surface of the metal silicon powder which adversely affects the crosslinking reaction of the organopolysiloxane during sheet molding.

Although the average particle diameter of the thermally conductive powder used by this invention is not specifically limited, It is preferable that it is 0.1-50 micrometers, It is especially preferable that it is 0.5-20 micrometers, and also 1-10 micrometers. If the average particle diameter is less than 0.1 mu m, the specific surface area of the powder becomes relatively large, so that high filling becomes difficult, the thermal conductivity becomes insufficient, and the rubber after curing may be too hard. On the other hand, when the average particle diameter is larger than 50 µm, the rubber after curing becomes fragile and unevenness tends to occur on the surface, which is not preferable.

Although the compounding quantity of (B) component in this invention needs to be 50-250 mass parts with respect to 100 mass parts of (A) component, It is preferable to use especially in the range of 70-200 mass parts. When it is more than 250 parts by mass, not only the compounding becomes difficult, but also the moldability deteriorates. If the amount is less than 50 parts by mass, the thermal conductivity is insufficient.

(C) Ingredients:

Carbon black, which is the component (C) used in the present invention, improves the mechanical strength of the silicone rubber sheet, in particular, the mechanical strength at the time of heating to improve heat resistance, and at the same time, imparts thermal conductivity and antistatic properties by conducting electrical conductivity. It is.

Carbon black is classified into furnace black, channel black, thermal black, acetylene black and the like by the production method thereof, and usually contains impurities such as sulfur. In this invention, it is preferable to use the thing whose volatile matters other than water are 0.5 mass% or less. In particular, acetylene black is preferred because it contains less impurities.

The measuring method of volatile matters other than the said water is described in the "carbon black test method for rubber | gum" of JISK6122. 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 that the average particle diameter of carbon black of (C) component is the range of 10-300 nm, and it is especially preferable that it is the range of 15-100 nm. In addition, the BET specific surface area is preferably 20 to 300 m 2 / g, and particularly preferably 30 to 200 m 2 / g.

The compounding quantity of (C) component in this invention is 5-60 mass parts with respect to 100 mass parts of (A) component, It is preferable to use especially in the range of 10-55 mass parts. If it is less than 5 parts by mass, the improvement of thermal conductivity and heat-compression resistance is insufficient, and if it exceeds 60 parts by mass, it becomes difficult to mix uniformly, and the molding processability of the resulting composition is very poor.

(D) Ingredients:

The reinforcing silica fine powder having a BET specific surface area of 50 m 2 / g or more, which is the component (D) used in the present invention, is used as a reinforcing component of silicone rubber. Although this fine powder silica may be hydrophilic or hydrophobic, it is preferable that the BET specific surface area is 50-800 m <2> / g from a viewpoint of a reinforcement effect, and 100-500 m <2> / g fine powder silica is especially preferable. If the specific surface area is less than 50 m 2 / g, the reinforcing effect cannot be sufficiently obtained.

Although the compounding quantity of (D) component in this invention is 0-40 mass parts with respect to 100 mass parts of (A) component, It is more preferable that it is 5-35 mass parts, It is especially preferable that it is 10-30 mass parts. When more than 40 mass parts, the plasticity of a silicone rubber composition becomes high too much and moldability may worsen, or the rubber after hardening may become too hard.

In addition, in this invention, it is necessary for the total amount of a component (C) and a component (D) to be 10-60 mass parts, and it is preferable that it is 20-50 mass parts. If it is less than 10 mass parts, the strength of the obtained silicone rubber will become inadequate, and if it exceeds 60 mass parts, not only it will become difficult to mix | blend uniformly, but also the plasticity of the composition obtained will become high too much, and moldability is very bad.

(E) Ingredients:

The hardening | curing agent which is (E) component used by this invention can be suitably selected from a well-known thing normally used for hardening of a silicone rubber, and can be used. As such a hardening | curing agent, for example

a) organic peroxides such as di-t-butylperoxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane and dicumylperoxide used for the radical reaction;

b) When organopolysiloxane of (A) component has an alkenyl group, it is an addition reaction hardening | curing agent, Organohydrogenpolysiloxane containing 2 or more of hydrogen atoms couple | bonded with the silicon atom in 1 molecule, platinum, palladium, etc. Combination with a platinum group metal catalyst; Etc. are illustrated. In this invention, although the addition reaction hardening | curing agent of b) is preferable from the reasons of being easy to control reaction, a reaction residue is not left, etc., both can also be used together as needed. Although the addition amount of these hardening | curing agents can be performed similarly to the case of normal silicone rubber, it is generally as follows.

About the hardening | curing agent a), 0.1-20 mass parts is used per 100 mass parts of organopolysiloxane of (A) component.

About the hardening | curing agent b), the organohydrogensiloxane containing 2 or more of hydrogen atoms couple | bonded with the said silicon atom in 1 molecule is couple | bonded with the silicon atom which the said organohydrogensiloxane has per mole of alkenyl groups of (A) component A range in which the amount of hydrogen atoms to be 0.5 to 5 moles is used, and the amount of the platinum group metal catalyst is 0.1 to 1000 ppm (mass basis) as the metal component with respect to the component (A).

In order to control the hardness and elongation of the silicone rubber sheet of the present invention so that the lead electrodes can be narrowly connected to each other with high accuracy using an anisotropic conductive film, the interaction between the filler powder and the silicon molecules is similar to the degree of crosslinking between the silicon molecules. Needs to be controlled to an appropriate range. The degree of crosslinking between the silicone molecules can be easily controlled by controlling the addition reaction, and in particular, in the case of a miracle type silicone rubber having a high degree of polymerization, it can be controlled by controlling the content of vinyl groups involved in the crosslinking. In the case of silicone rubber, it is known that the interaction between the silicon molecules and the filler powder has a large interaction due to pseudo crosslinking by hydrogen bonding between the silicon molecules and the reinforcing silica. Therefore, in the case of silicone rubber which makes hardening by addition reaction the main crosslinking reaction, the hardness and the hardness of the silicone rubber sheet of this invention are controlled by controlling two factors, the content rate of a vinyl group and the compounding quantity of reinforcement silica, in an optimal range. Elongation can be adjusted to a preferable range.

Specifically, 0.10 to 0.30 mol% of the total R contained in the side chains of all the organopolysiloxane molecules of the component (A) are vinyl groups, and the total amount of the side chains of the entire organopolysiloxane molecule of the component (A) is included. The sum (P + Q) which added the numerical value (Q) which divided the mass part with respect to 100 mass parts of (A) component of the reinforcement silica fine powder which is (D) component to 100 mol% of vinyl groups of (D) is 0.20- After adjusting (A) component and (D) component so that it may be set to 0.50, the hardness and elongation of the silicone rubber sheet of this invention can be adjusted to a preferable range by making addition reaction and hardening.

When the total value of the above (P + Q) is less than 0.20, the sum of the crosslinking point by the addition reaction and the pseudo crosslinking point by the hydrogen bonding of the reinforcing silica fine powder and the silicon molecules is insufficient, so that the elongation is not too large, Hardness also becomes insufficient. On the contrary, when it exceeds 0.50, since the sum total of a crosslinking point and a pseudo crosslinking point becomes too large, elongation will become too small, a sheet will become weak, durability will fall, and it will become too hard, and cushioning property will become inadequate.

Other ingredients

In the silicone rubber composition of the present invention, if necessary, heat-resistant imparting agents such as cerium oxide, iron oxide, titanium oxide, fillers such as clay, calcium carbonate, diatomaceous earth, titanium dioxide, dispersing agents such as low molecular siloxane ester and silanol, Adhesion-imparting agents, such as a silane coupling agent and a titanium coupling agent, the platinum group metal type compound which gives a flame retardance, tetrafluoro polyethylene particle which raises the green strength of a rubber compound, etc. can also be added.

Manufacture and processing

Although the silicone rubber composition used for this invention can be knead | mixed each component to be used using mixers, such as a biaxial roll mill, a kneading machine, and a Benbury mixer, it is generally good to add only before hardening agent is used. It is preferable to knead | mix other components beforehand.

As a molding method of the silicone rubber sheet of the present invention, a silicone rubber composition containing all components up to the curing agent is cured by dividing the cured silicone rubber into a predetermined thickness with a calender or an extruder, or a solvent such as a liquid silicone rubber composition or toluene. The method etc. which harden after melt | dissolving and liquefying the silicone rubber composition on the film are mentioned.

The thickness of the silicone rubber sheet molded and cured in this manner is 0.05 to 1 mm, particularly preferably 0.1 to 0.8 mm. If the thickness is less than 0.05 mm, the cushioning property is insufficient, and uniform pressure transmission becomes impossible. On the other hand, when the thickness exceeds 1 mm, heat transfer deteriorates.

Hereinafter, although an Example further demonstrates this invention, this invention is not limited by these in any way.

In the following examples, the following materials were used.

Organopolysiloxanes:

(a-1) Methylvinylpolysiloxane with both ends of the molecular chain sealed with dimethylvinylsiloxy groups having an average degree of polymerization of 8,000 containing 99.85 mol% of dimethylsiloxane units and 0.15 mol% of methylvinylsiloxane units

(a-2) Methylvinylpolysiloxane having both ends of the molecular chain sealed with dimethylvinylsiloxy groups having an average degree of polymerization of 8,000, containing 99.5 mol% of dimethylsiloxane units and 0.5 mol% of methylvinylsiloxane units.

Thermally conductive fillers:

(b-1) Metal silicon pulverized powder with an average particle diameter of 5 micrometers (the surface was forced-oxidized)

(b-2) Crystalline silicon dioxide pulverized powder having an average particle diameter of 4 μm

(b-3) Grinding aluminum oxide powder having an average particle diameter of 4 µm

Carbon black powder:

(c-1) Acetylene black having an average particle diameter of 35 nm, volatile matter other than water, 0.10 mass%, and BET specific surface area of 69 m 2 / g

Reinforcing Silica Fine Powder:

(d-1) Reinforcing silica fine powder having a BET specific surface area of 300 m 2 / g (trade name: Aerosil 300, manufactured by Nisbon Aerosil Co., Ltd.)

Curing agent:

(e-1) Vinyl siloxane complex of platinum chloride (platinum content 1 mass%)

(e-2) Methylhydrogenpolysiloxane represented by the following formula (1)

Other Ingredients:

(f-1) Dimethyldimethoxysilane

(g-1) cerium oxide powder having a BET specific surface area of 140 m 2 / g

(h-1) ethynylcyclohexanol

<Example 1>

As the component (A), 100 parts by mass of the base consisting of 60 parts by mass of (a-1) and 40 parts by mass of (a-2) were used, and as the component (D), 20 parts by mass of (d-1) and the component (D) were used. As the surface treating agent, 3 parts by mass of (f-1) and 1 part by mass of ion-exchanged water were blended and kneaded while heating at 170 ° C. for 2 hours using a kneading machine to homogenize.

To 123 parts by mass of the obtained silicone rubber composition, 130 parts by mass of (b-1) as the component (B), 10 parts by mass of (c-1) as the component (C) and 0.5 mass of (g-1) as the heat-resistant improving agent Part was added and blended and kneaded for 15 minutes using a pressure kneader to homogenize.

To 100 parts by mass of the obtained silicone rubber composition, 0.05 parts by mass of (e-1), 0.025 parts by mass of (h-1) which is a control agent of the platinum catalyst, and 0.7 parts by mass of (e-2) were sequentially kneaded with a biaxial roll mill. It added in the order mentioned above, and prepared curable silicone rubber composition (I).

The silicone rubber composition obtained by using a calender molding machine was cut out to a thickness of 0.25 mm, and then transferred onto a polyethylene terephthalate (PET) film having a thickness of 100 µm. The sheet-like silicone rubber composition was cured by passing through a 150 degreeC heating furnace for 5 minutes as it is in the state of the laminated product with a PET film. The PET film was peeled from the obtained sheet-like composition, and heat-treated in a 200 degreeC dryer for 4 hours, and the silicone rubber sheet for thermocompression bonding of 0.25 mm in thickness was produced.

<Example 2>

As component (A), 100 parts by mass of (a-2), 140 parts by mass of (b-2) as components (B), 50 parts by mass of (c-1) as components (C) and (g) -1) 0.5 mass part was mix | blended using a pressure kneader, it knead | mixed for 15 minutes, and it was uniformized. 0.1 mass part of (e-1), 0.04 mass part of (h-1) which is a control agent of a platinum catalyst, and 1.0 mass part of (e-2) are added with respect to 100 mass parts of obtained silicone rubber compositions, and it uses a biaxial roll mill. The mixture was sufficiently kneaded to prepare a curable silicone rubber composition (II), and molded and cured in the same manner as in Example 1 to produce a silicone rubber sheet having a thickness of 0.25 mm.

<Example 3>

A silicone rubber sheet having a thickness of 0.25 mm was produced in the same manner as in Example 1, except that 220 parts by mass of (b-3) was used instead of the component (B) used in Example 1.

Comparative Example 1

As component (A), 100 parts by mass of (a-2), 30 parts by mass of (d-1) as components (D), 0.1 parts by mass of (e-1), and 0.04 parts by mass of (h-1) A silicone rubber sheet having a thickness of 0.25 mm was produced in the same manner as in Example 1 except that 1.0 parts by mass of (e-2) were used.

Comparative Example 2

A silicone rubber sheet having a thickness of 0.25 mm was produced in the same manner as in Example 2, except that (a-1) was used instead of (a-2) as the component (A).

Comparative Example 3

As the component (A), 100 parts by mass of the base consisting of 50 parts by mass of (a-1) and 50 parts by mass of (a-2) were used, and (f-1) 3 parts by mass of the surface treating agent of the component (D) and ions 1 mass part of exchange water was used, and it mix | blended and kneaded, heating at 170 degreeC for 2 hours using the kneading machine, and it was made uniform. To 153 parts by mass of the obtained silicone rubber composition, 320 parts by mass of (b-1) was added as the component (B), and blended and kneaded for 15 minutes using a pressure kneader to homogenize. With respect to 100 mass parts of obtained silicone rubber compositions, 0.8 mass parts of (e-3) are knead | mixed uniformly using a biaxial roll mill, the curable silicone rubber composition (III) was manufactured, and the primary vulcanization temperature was 170 degreeC. In the same manner as in Example 1, a silicone rubber sheet having a thickness of 0.25 mm was produced by curing.

[Evaluation of Basic Properties]

Hardness, tensile strength and elongation at break were measured in accordance with JIS K6249. However, about hardness, the sheet | seat produced using the type A durometer was measured repeatedly so that thickness might be 6 mm or more. Tensile strength and elongation at break were measured using a specimen of Dumbbell No. 2 type.

In addition, the thermal conductivity was measured in accordance with the provisions of ASTM E 1530.

[Thickness reduction rate after 100 times of pressing]

The silicone rubber sheet was set only on the back-up tool of the press, and the heat tool heated to 400 ° C. was pressurized for 10 seconds directly at a pressing force of 4 MPa, and the operation was continuously performed 100 times with an interval of 10 seconds.

[(Initial thickness of sheet)-(thickness after 100 times crimping of sheet)] / initial thickness of sheet

The number described as a percentage was made into the thickness reduction rate after 100 times crimping.

[Narrow pitch connection evaluation]

As shown in FIG. 1, 50 copper electrode 1a is 32 micrometer pitch (line width 16 micrometers, 16 micrometers space | interval), and 50 ITO electrode 1b is 32 micrometer pitch similarly to FPC (flexible printed wiring board). The glass plate 2b provided with (16 micrometers in line width, 16 micrometers in space) is made so that the surface of the side which provided each copper electrode 1a and the ITO electrode 1b may mutually face each other, and thickness is 22 micrometers between them, The ACF (anisotropic conductive film) 3 having a width of 1.2 mm was sandwiched and mounted on the backup tool 4 of the compactor. Subsequently, the silicone rubber sheet 5 for thermocompression bonding produced in Examples 1-3 or Comparative Examples 1-3 was attached so that the upper surface of FPC2a mentioned above may be contacted. Subsequently, the pressurization tool 6 heated at 350 degreeC was pressurized for 10 second from the said silicone rubber sheet 5 by the pressing force of 4 MPa. Thus, after ACF 3 was crimped | bonded between FPC2a and the glass plate 2b, electrical conduction between the copper electrode 1a and the ITO electrode 1b was evaluated. The results are shown in Table 1 below.

In the case of the thermocompression-bonding silicone rubber sheet of the present invention produced in Examples 1 to 3, connection corresponding to a narrow pitch was possible, but when too hard as in Comparative Example 1, cushioning properties were insufficient, so that conduction between electrodes This was not complete. In addition, the sheets obtained in Comparative Examples 1 and 3 were very fragile and cracked in the sheets when folded. On the other hand, in the case of the comparative example 2, since the elongation of the sheet was too large and the position shift of the electrode generate | occur | produced, the conduction defect occurred.

Industrial availability

The silicone rubber sheet for thermocompression bonding of the present invention has excellent thermocompression durability at a high temperature of 300 ° C. or higher, and is not only deteriorated due to permanent deformation even after repeated compression at 300 ° C. or higher, but also has good durability against mechanical breakdown. In addition, the elongation at the time of cutting is not only appropriately small, but also has an appropriate hardness and an appropriate thermal conductivity. It is suitable for phosphorus thermocompression bonding.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram explaining the method of thermocompression bonding ACF inserted by FPC using the silicone rubber sheet for thermocompression bonding of this invention.

<Brief description of symbols for the main parts of the drawings>

1a: copper electrode

1b: ITO electrode

2a: flexible printed wiring board

2b: glass plate

3: anisotropic conductive film

4: backup tool (support)

5: silicone rubber sheet for thermocompression bonding

6: heating / pressurization tool

Claims (8)

(A) organopolysiloxane with an average degree of polymerization of 3000 or more: 100 parts by mass (B) at least one thermally conductive powder selected from metals, metal oxides, metal nitrides and metal carbides: 50 to 250 parts by mass (C) carbon black powder: 5 to 60 parts by mass (D) Reinforcing silica fine powder having a BET specific surface area of 50 m 2 / g or more: an amount of 0 to 40 parts by mass, wherein the total amount of components (C) and (D) is 10 to 60 parts by mass, and (E) curing agent A silicone rubber sheet formed by molding a silicone rubber composition comprising a sheet into a sheet and cured, wherein the elongation at break at 23 ° C. is 50 to 120% and the hardness at 23 ° C. measured by a type A durometer is 65 to At the same time, the thermal conductivity is 0.5 to 1.0 W / mK, silicone rubber sheet for thermocompression, characterized in that. The organopolysiloxane according to claim 1, wherein the organopolysiloxane having an average degree of polymerization of 3000 or more as the component (A) is represented by the following average compositional formula 1, and includes at least one organopolysiloxane including an organopolysiloxane having at least two alkenyl groups in one molecule. Composed of polysiloxane molecules, 0.10 to 0.30 mol% of the total R contained in the organopolysiloxane molecule of the component (A) is a vinyl group, and to the total vinyl group amount P (mol%) of the organopolysiloxane molecule of the component (A), the component (D) While adjusting the usage-amount of the said (A) component and (D) component so that the value of the sum (P + Q) which added the numerical value Q divided by the mass part of reinforcement silica powder of 100 by 0.20 to 0.50, (E) A silicone rubber sheet for thermocompression bonding comprising a organohydrogenpolysiloxane having a hydrogen atom bonded to at least two silicon atoms in one molecule and a platinum-based catalyst. <Mean Composition 1> R _n SiO _{(4-n) / 2} However, n in average composition formula 1 is a positive number of 1.9-2.4, R represents a substituted or unsubstituted monovalent hydrocarbon group, 0.0001-10 mol% of R in each molecule is a vinyl group, 80 mol% or more Methyl group. The silicone rubber sheet for thermocompression bonding according to claim 1 or 2, wherein the thermally conductive powder (B) is a metallic silicon powder. The silicone rubber sheet for thermocompression bonding according to claim 3, wherein the metal silicon powder is a ground powder having an average particle diameter of 1 to 20 µm. The silicone rubber sheet for thermocompression bonding according to claim 3, wherein the metal silicon powder is a spherical powder having an average particle diameter of 1 to 20 µm. The silicon rubber sheet for thermocompression bonding according to claim 3, wherein a forced oxide film is formed on the surface of the metal silicon powder. The silicone rubber sheet for thermocompression bonding according to claim 1 or 2, wherein the thermally conductive powder (B) is a crystalline silicon dioxide powder having an average particle diameter of 1 to 20 µm. The silicone rubber sheet for thermocompression according to claim 1 or 2, wherein the thickness is in the range of 0.05 to 1 mm.

Images