JPH0660282B2 - Heat resistant silicone gel composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention is excellent in heat-resistant silicone gel composition, particularly in electrical characteristics, moisture-proof and anti-fouling property, heat resistance, cold resistance, and low elastic modulus. , A heat-resistant silicone gel useful as a protective agent for IC, hybrid IC and the like.

[Prior Art] Silicone gel compositions have been used as a protective agent for ICs and hybrid ICs in recent years because of their excellent electrical properties, moisture-proof and antifouling properties, heat resistance, and cold resistance. Since the components themselves have become weak in mechanical strength with the recent miniaturization and weight reduction of electric and electronic parts, the silicone gel composition for protecting these elements is stressed to the elements. It is becoming an indispensable condition to make it small.

[Problems to be Solved by the Invention] However, the internal stress α of the gel is α = k · λ · E · ΔT (where k = constant, λ = coefficient of thermal expansion, E = elastic modulus, ΔT
= Temperature difference), it is necessary to reduce the coefficient of thermal expansion or the modulus of elasticity in order to reduce this stress α. In this case, since it is fixed, the elastic modulus is lowered as an actual measure.

[Problems to be Solved by the Invention] As this method, a technical method already known to those skilled in the art for reducing the crosslink density is used,
However, with a JIS-K 2220 consistency tester, 1/4 penetration is 100-
When the softness is 130 levels, there is a problem that the penetration, that is, the elastic modulus, changes due to a long-term cooling / heating cycle in mounting, and it becomes difficult to maintain the performance at the time of initial design.

[Means for Solving the Problems] The present invention has solved the above problems and is a composition that retains the properties at the time of initial setting for a long period of time, particularly heat resistance with a small change in elastic modulus under a long-term thermal history. The present invention relates to a silicone gel composition, which provides a silicone composition useful as a protective potting and sealing material for ICs, hybrid ICs, etc., which is 1) having 2 to 2 carbon atoms in one molecule.
A general formula containing an average of 0.1 to 2 aliphatic unsaturated groups of 8 R ¹ is a vinyl group, an allyl group, a propenyl group,
An aliphatic unsaturated group having 2 to 8 carbon atoms such as butenyl group, R
² is an alkyl group such as a methyl group, an ethyl group, a propyl group and a butyl group, an aryl group such as a phenyl group and a tolyl group,
Or an unsubstituted or substituted monovalent hydrocarbon group selected from 3,3,3-trifluoropropyl group and the like, and a and b are 0.
0001 <a <0.05, 1.8 <b <2.2 and 1.8 <a + b <2.205 where organopolysiloxane prepared by equilibration with alkali metal hydroxide of organopolysiloxane or its silanolate, 2) in the first component The amount of the group having a hydrogen atom bonded to a silicon atom is 0.8 to 1.1 mol per 1 mol of the aliphatic unsaturated group, the general formula , R ² is the same as above, c is 1.8 <c <2.2, and d is
Organohydrogenpolysiloxane having an average of two or more groups having a hydrogen atom bonded to a silicon atom in one molecule, wherein 0.002 ≦ d ≦ 1.0 and c + d is 1.8 <c + d ≦ 3.0, 3) the above Hydroxyl consisting of a 0-valent platinum compound in an amount of 0.1 to 100 ppm as a platinum element with respect to the total amount of the first component and the second component, and being directly bonded to a silicon atom in the total amount of the first to third components. It is characterized by containing 150 ppm or less of a group.

That is, the present inventors have conducted various studies to develop a heat-resistant silicone gel composition that is useful as a protective agent for ICs, packaged ICs, etc., and as a result, have found that this gel has an average of 0.1 to 2 aliphatic groups in one molecule. An organopolysiloxane having an unsaturated group and a predetermined amount of an organohydrogenpolysiloxane and a platinum compound as a catalyst for addition reaction, and a hydroxy group content comprising an organopolysiloxane composition of 150 ppm or less, It was found that this product has excellent electrical properties, moisture-proof and anti-fouling property, heat resistance and cold resistance, and has a small elastic modulus, which makes it useful as a protective agent for IC and the like. The present invention was completed by conducting research on the amount and the like.

[Function] The heat-resistant silicone gel composition of the present invention is
It is assumed to consist of the third component.

The organopolysiloxane as the first component constituting the heat-resistant silicone gel composition of the present invention has an average of 0.1 to 2.0 aliphatic unsaturated groups having 2 to 8 carbon atoms in one molecule, and has the general formula R ¹ is a vinyl group, an allyl group, a propenyl group,
An aliphatic unsaturated group having 2 to 8 carbon atoms such as butenyl group, R ² is an alkyl group such as methyl group, ethyl group, propyl group, butyl group, aryl group such as phenyl group, tolyl group, or 3 An unsubstituted or substituted monovalent hydrocarbon group selected from 3,3,3-trifluoropropyl group, a,
b is 0.0001 <a <0.05, 1.8 <b <2.2 and 1.8 <a + b <
2.205, which may be linear or branched, but here, the aliphatic unsaturated group is not available because of its availability of raw materials, reactivity with Si-H group, etc. From the viewpoint, a vinyl group is preferable. The end of the molecular chain is preferably blocked with a triorganosiloxy group such as a trimethylsiloxy group, a vinyldimethylsiloxy group, a divinylmethylsiloxy group, a trivinylsiloxy group, a vinylmethylphenylsiloxy group.

This organopolysiloxane is typically a diorganocyclopolysiloxane such as hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, tetravinyltetramethylcyclotetrasiloxane and R ₃ Si
An organosiloxane having _0.5 units of O (R is a monovalent hydrocarbon group) and a hydroxide of an alkali metal such as lithium, sodium, potassium, or cesium or its silanolate, tetramethylammonium hydroxide, tetramethylphosphonium hydroxide, tetra It has already been produced by a polymerization equilibration reaction with a strongly basic catalyst such as butylammonium hydroxide, tetrabutylphosphonium hydroxide or its silanolate, sulfuric acid, fuming sulfuric acid, trifluoromethanesulfonic acid, methanesulfonic acid, etc. As is well known, the diorganopolysiloxane used in the present invention may be polymerized and equilibrated by using an alkali metal hydroxide or its silanolate as a catalyst from the viewpoints of heat resistance stability and electric property retention. Is required. When this reaction is carried out in the presence of a catalyst containing an amine and a phosphorus compound, it has an advantage that it can be polymerized at a low temperature because of its high polymerization activity, but from the obtained organopolysiloxane, elements such as N and P are added. It is difficult to completely remove these elements, and if these elements normally remain in the addition-curing type silicone elastomer in the range of several ppm to 1 ppm, no particular problems occur. Disadvantages are that the variation between lots becomes large and adjustment becomes necessary, and the cured gel has a large effect on elements such as ICs, and these impurities cause an increase in leakage current over time, which causes quality problems. There is. Further, when an acidic catalyst is used, the catalyst can be removed in a water washing step when the viscosity of the diorganopolysiloxane is 100 cS or less.
It is often set at 500 to 1,500 cS, in which case it is difficult to separate it from water, and its production becomes impossible from an economical point of view. Next, as the second component constituting the composition of the present invention, Organohydrogenpolysiloxane is said to contain at least two groups containing hydrogen atoms bonded to silicon atoms (≡SiH groups) in one molecule, but essentially one molecule contains ≡SiH groups. It is preferable that three or more contained molecules intervene. Therefore, this organohydrogenpolysiloxane may be obtained by an equilibration reaction, or may be, for example, a mixture of one containing 3 or more ≡SiH groups and one containing less ≡SiH groups. The cured product has only to have a very small elastic modulus, and it contains HR ₂ SiO _1/2 units, HRSiO _2/2 units, HSiO _3/2 (R is a monovalent hydrocarbon group). Good. In addition, this may be linear or branched, but one having two hydrogen atoms bonded to one silicon atom should not be used from the viewpoint of stability. Further, this can be usually obtained by an equilibration reaction in the presence of an acid catalyst, but since this product has a low viscosity of usually 100 cS or less, it can be easily washed with water, so there is no problem even if it is produced by an acid catalyst. .

The blending amount of this organohydrogenpolysiloxane is the same as that of the organopolysiloxane as the first component and the second component.
After the addition reaction with this organohydrogenpolysiloxane as a component, an aliphatic unsaturated group and ≡SiH
If the group remains as a reaction residue, the heat resistance of the cured silicone gel becomes poor, so this aliphatic unsaturated group and ≡Si
It is preferable that the H groups be as equimolar as possible, but the addition reactivity between the ≡SiH group and the aliphatic unsaturated group differs depending on the structure, and this reactivity is generally HR ₂ SiO _2.
Since it is assumed that _0.5 >HRSiO> HSiO _1.5 , practically, in consideration of these points, the range of ≡SiH group is 0.8 to 1.1 mol with respect to 1 mol of the aliphatic unsaturated group in the first component. The amount should be

Further, the platinum compound as the third component constituting the composition of the present invention is a known one which is used as a catalyst for the addition reaction of the organopolysiloxane having an aliphatic unsaturated hydrocarbon group and the organohydrogenpolysiloxane. However, the known rhodium compound cannot be practically used in a system having a low crosslinking density such as the silicone gel composition of the present invention because it accelerates the hydrolysis reaction of the ≡SiH group in the organohydrogenpolysiloxane. Therefore, this needs to be a platinum compound, and examples thereof include alcohol complexes of chloroplatinated platinic acid, vinylsiloxane complexes, alkyne complexes, enyne compound complexes, phosphorus compound complexes, nitrogen compound complexes, and the like. Particularly, a platinum complex of vinyl siloxane is preferably used. The platinum compound has a Cl content of 0.1 ppm, which is essentially 0, from the viewpoint of heat resistance of the desired silicone gel composition, prevention of depolymerization reaction, prevention of coloration, and retention of electrical characteristics. Although it is required to have a valency, the blending amount may be 0.1 to 100 ppm with respect to the total amount of the first component and the second component described above.

The heat resistant silicone gel composition of the present invention is
Although it can be obtained by mixing a predetermined amount of the third component, this composition has a silanol group (≡SiOH) when used in combination with another organic resin (eg, epoxy resin) from the viewpoint of heat resistance. ) Remains adversely, and the long-term heat resistance of the silicone gel after curing is impaired. That is, The silanol in this composition gives rise to disadvantages such as changing the elastic modulus of the silicone gel with time to raise or lower the elastic modulus, and causing it to flow out as an oily substance. The content of the group needs to be 150 ppm or less.

Therefore, it is necessary to reduce the residual amount of silanol groups in the above-mentioned first component and second component that compose this composition, but this first component depends on the alkali metal hydroxide. Polymerization and equilibration do not always give good results as compared with the case of using other polymerization catalysts, but this problem is a method of neutralizing this polymer with a chlorosilane-silazane system (see JP-B-61-12931). ) Will be solved. Further, since the silanol group is affected by the amount of catalyst, it is also effective to reduce this amount. on the other hand,
It is also known that a branched organopolysiloxane oil has good low temperature characteristics (see Japanese Patent Publication No. 61-16295).
However, although a method for producing such an oil has not been clarified in detail in this specification, as shown in the example (C
When a cohydrolyzate of H ₃ ) ₃ SiO _1/2 (CH ₃ ) ₂ SiO and CH ₃ SiO _3/2 units is used, the residual amount of silanol groups becomes extremely large, resulting in poor heat resistance. As a method for reducing the silanol groups of the branched organopolysiloxane oil containing such CH ₃ SiO _3/2 units, Is preferred as a CH ₃ SiO _3/2 unit (see Japanese Patent Application Laid-Open No. 63-256614), and even when such a compound is used, the catalyst amount is reduced and the chlorosilane-silazane system (for example, trimethyl) is used. Chlorosilane or vinyldimethylchlorosilane and hexamethylsilazane or 1,
A neutralization method using 3-divinyl-1,1,3,3-tetramethyldisilazane and the like) is effective for further reducing the silanol groups in the oil. Also,
For this second component, it is preferable to reduce the amount of catalyst in the equilibration reaction to increase the molecular weight as much as possible to reduce the end groups, or neutralize with excess silazane.

As described above, the heat resistant silicone gel composition of the present invention has a silanol group content of substantially 150 ppm.
It consists of the above-mentioned first to third components, which are the following, but it is not necessary to add various additives to this composition in order to improve this property or impart other properties. It is optional as long as it does not impair the purpose, in particular, inorganic fillers such as fumed silica, ground silica, SiO ₂ compounds such as fused silica, colorants such as red iron oxide, titanium oxide and carbon black, or gels having a low specific gravity. It is effective to add silica hollow filler, organic hollow filler, etc. for comparison, but pay close attention to the water content in this addition, and presume that such steps as dehydration have been taken. There is a need to. Further, although this composition is useful as a protective agent for ICs and the like, when it is used for this purpose, it is necessary to consider prevention of curing failure due to solder flux. It is preferable to add a ketene acetal compound (see JP-A-63-165455).

This additive reacts easily with silanol groups or H ₂ O,
It is very useful for the purpose of the present invention because it is effective in eliminating these compounds, and the ester compound formed at that time is chemically neutral and not reactive.

[Examples] Next, synthesis examples, examples, and comparative examples of the organopolysiloxane as the first component constituting the heat-resistant silicone gel composition of the present invention will be described. Parts in the examples are parts by weight. The viscosity is the value measured at 25 ° C.

Synthesis Example _{1 [(CH 3) 3 SiO} -Si (CH 3) 2] 2 O 22g, [(CH 3) 2 SiO] 4 1,600
g, the _{[CH 2 = CH (CH 3} ) 2 Si] siloxane mixture consisting of _{2 O5.4g,} 5% KOH- dimethylpolysiloxane siloxanolate 2.5g
Was added and a polymerization reaction was carried out at 150 ° C. for 8 hours, and then a mixed solution of 0.4 g of (CH ₃ ) ₃ SiCl and ₄ g of [(CH ₃ ) ₃ Si] ₂ NH was added to this reaction solution, and the mixture was heated at 50 ° C. for 2 hours. The mixture was stirred for a period of time to carry out neutralization treatment, then heated at 150-160 ° C. under reduced pressure of 2 mmHg for 8 hours to distill off low-boiling-point components, and the formed salt was filtered off to obtain a viscosity of 800 cp.
To obtain a transparent organopolysiloxane (hereinafter abbreviated as AI). The silanol group content of this product was measured and found to be 50 ppm.

Further, 5 g of ethylene chlorohydrin as a neutralizing agent was added to the reaction solution obtained above, and the mixture was stirred at 110 to 120 ° C. for 4 hours, then the low fraction was distilled off in the same manner as above, and the produced salt was filtered off. Obtained organopolysiloxane (hereinafter abbreviated as A-II)
Is a transparent material with a viscosity of 830 cp and the silanol group content is 2
It was 00 ppm.

Synthesis Example _{2 (CH 3) 3 SiO [} Si (CH 3) 2 O] 10 Si (CH 3) 3 198g, CH 2 = CH (CH 3) 2
_{SiO [Si (CH 3) 2} O] 10 Si (CH 3) 2 CH = CH 2 46g, To a mixture of 1,700 g of [(CH ₃ ) ₂ SiO] ₄ and 240 g of xylene, 5.5 g of 5% KOH-dimethylpolysiloxanolate was added, and a polymerization reaction was carried out at 150 ° C. for 8 hours. A mixture of 2.7 g of CH ₃ ) ₃ SiCl and 24 g of [(CH ₃ ) ₃ Si] ₂ NH was added, and the mixture was stirred at 120 ° C. for 2 hours for neutralization treatment, and then 150-160 under reduced pressure of 2 mmHg. When heated to 8 ° C for 8 hours to distill off low-boiling-point components and the formed salt was filtered off, the viscosity was
An organopolysiloxane (hereinafter abbreviated as BI) having a silanol group content of 100 ppm at 1,500 cp was obtained.

Further, 12 g of ethylene chlorohydrin was added as a neutralizing agent to the reaction solution obtained above, and the mixture was stirred at 110 to 120 ° C. for 4 hours, then the low fraction was removed in the same manner as above, and the produced salt was filtered off. As a result, an organopolysiloxane (hereinafter abbreviated as B-II) having a viscosity of 1,800 cp and being transparent and having a silanol group content of 300 ppm was obtained.

Example 1, Comparative Example 1 Organopolysiloxane A-I100 obtained in Synthesis Example 1
Separate component, CH ₃ HSiO units 37 mole%, (CH _{3) 2} SiO units 62 mole% and (CH _{3) 3} methylhydrodiene polysiloxane 0.7 parts made of SiO _0.5 units 1 mol% of tetramethyltetravinylcyclotetrasiloxane After 0.01 part was added and mixed uniformly, a vinylsiloxane complex of chloroplatinic acid was added thereto in an amount such that the amount of platinum was 5 ppm with respect to the total amount of this mixture, and the mixture was uniformly mixed to obtain a silicone gel composition I. Had made.

Separately, for comparison, 100 parts of the organopolysiloxane A-II obtained in Synthesis Example 1 was mixed with the same methylhydrogenene polysiloxane, tetramethyltetravinylcyclotetrasiloxane, and vinylsiloxane complex salt of chloroplatinic acid as described above. Silicone gel composition II was prepared by adding the same amount.

Example 2, Comparative Example 2 Organopolysiloxane B-I100 obtained in Synthesis Example 2
In part, (CH _{3) 2} SiO units 90 mole%, methylhydrodiene polysiloxane 3.5 consisting of H (CH _{3) 2} SiO _0.5 units 10 mole%
Parts and ethynylcyclohexanol 0.04 parts were added and mixed uniformly, and then a vinylsiloxane complex of chloroplatinic acid was added thereto in an amount such that the amount of platinum was 5 ppm with respect to the total amount of this mixture, and the mixture was uniformly mixed to obtain silicone. Gel composition-III
made.

Separately, for comparison, 100 parts of the organopolysiloxane B-II obtained in Synthesis Example 2 was added with the same amount of the same methylhydrogenene polysiloxane, ethynylcyclohexanol, and vinylsiloxane complex of chloroplatinic acid as above. A silicone gel composition IV was prepared.

(Heat resistance test) Next, the silicone gel compositions I to IV obtained above were treated at 150 ° C.
After heating for 30 minutes at 30 ° C, all of them became transparent gel-like substances, so the penetration of this gel-like substance at room temperature (measured by the method according to JIS K-2220) and those of 200 ° C The penetration degree (same as above) when placed in an air circulating oven was measured, and the results shown in Table 1 below were obtained. The silicone gel compositions I prepared in Examples 1 and 2 were obtained. , III were confirmed to have better heat resistance than the silicone gel compositions II, IV prepared in Comparative Examples 1 and 2.

[Effect of the Invention] As described above, the heat-resistant silicone gel composition of the present invention comprises an organopolysiloxane containing 0.1 to 2 lower aliphatic unsaturated groups in a molecule, a predetermined amount of organohydrogenpolysiloxane and platinum. The present invention relates to a silicone gel composition composed of a compound and having a silanol group content of 150 ppm or less, which has a silanol group content of 150 ppm.
Since it is as small as the following, the elastic modulus is small, and therefore it has good heat resistance, and thus has an industrial advantage that it is particularly useful as a protective agent for IC, hybrid IC and the like.

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-63-280766 (JP, A) JP-A-63-35655 (JP, A) JP-A-62-39658 (JP, A) JP-A-60- 49033 (JP, A)

Claims (1)

[Claims] 1. A general formula prepared by equilibration with an alkali metal hydroxide or its silanolate. (Here, R ¹ is an aliphatic unsaturated group having 2 to 8 carbon atoms such as vinyl group, allyl group, propenyl group, and butenyl group, R ²
Is an unsubstituted or substituted monovalent carbon atom selected from an alkyl group such as a methyl group, an ethyl group, a propyl group and a butyl group, an aryl group such as a phenyl group and a tolyl group, or a 3,3,3-trifluoropropyl group. Hydrogen group, a and b are 0.00
01 <a <0.05, 1.8 <b <2.2 and 1.8 <a + b <2.205), the viscosity at 25 ° C is 100 to 5,000 cS, and an aliphatic unsaturated group having 2 to 8 carbon atoms is contained in one molecule. 0.1 ~ on average
2) Organopolysiloxane containing 2) 1) A general formula of an amount of 0.8 to 1.1 mol of a group having a hydrogen atom bonded to a silicon atom based on 1 mol of an aliphatic unsaturated group in the first component. (Here, R ² is the same as above, c is 1.8 <c <2.2, and d is 0.
002 ≦ d ≦ 1.0 and c + d is 1.8 <c + d ≦ 3.0), an organohydrogenpolysiloxane containing an average of two or more groups having a hydrogen atom bonded to a silicon atom in one molecule, 3). It is composed of a 0-valent platinum compound in an amount of 0.1 to 100 ppm as a platinum element with respect to the total amount of the first component and the second component, and is directly bonded to a silicon atom in the total amount of the first to third components. A heat-resistant silicone gel composition characterized by containing 150 ppm or less of the hydroxyl group.