JPH07300560A - Silicon composition - Google Patents

Abstract

PURPOSE:To obtain a silicon composition which has satisfactory infiltrating properties and is safe by adding a low-mol. methylsiloxane as a solvent to a mixture of a specific diorganopolysiloxane, a specific organohydrogenpolysiloxane, and a platinum catalyst. CONSTITUTION:This composition comprises (A) a diorganopolysiloxane having two or more Si-bonded vinyl groups, (B) an organohydrogenpolysiloxane having two or more directly Si-bonded hydrogen atoms, (C) a platinum catalyst, and (D) a low-mol. methylsiloxane represented by formula I or II (wherein L is 0-2 and m is 4-5) as a solvent, the amount of (D) being 200-4,000 pts.wt. per 100 pts.wt. the sum of (A), (B), and (C). The component (A) preferably comprises a polysiloxane backbone and methyl and phenyl groups as side chains. The number of the directly Si-bonded hydrogen atoms of the component (B) is especially preferably 0.5-4 per vinyl group of the component (A) when the composition is for infiltration use. The content of Na and Cl ions in the components (A) and (C) is desirably 2ppm or lower from the standpoint of deterioration of electronic parts. This composition is infiltrated into pores of an electronic part and then cured.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a silicone composition, and more particularly to a curable silicone composition useful as an impregnating agent and a coating agent for electronic parts.

[0002]

2. Description of the Related Art Conventionally, electronic parts such as transistors, diodes, resistors, capacitors, and capacitors obtained by compacting ceramic powder are resin-sealed with an epoxy resin composition. In this case, the sealing resin and the electronic parts are Usually, very small gaps and voids are likely to occur between them. If there are such gaps or voids, water, Cl
^- enters the components such as Na ^+, there is a problem that deteriorates the characteristics of the electronic components.

Therefore, in an electronic component after resin encapsulation, an addition reaction curable silicone composition comprising an organohydrogenpolysiloxane, a vinyl group-containing organopolysiloxane and a catalyst for the purpose of filling the above-mentioned gaps and voids (example JP-A-4-370151), electronic parts are treated to impregnate the composition or form a coating film on the surface of the electronic parts. Usually, in order to improve the impregnation property and coatability of such a silicone composition, the composition is diluted with a freon solvent, an aliphatic hydrocarbon solvent or an aromatic hydrocarbon solvent and then treated. However, the use of CFC-based solvents is strongly required to be restricted as a causative substance that destroys the ozone layer. The aliphatic hydrocarbon solvent or aromatic hydrocarbon solvent is generally highly toxic and has a problem of deteriorating the working environment.

[0004]

Therefore, the present invention does not use a conventionally used CFC solvent or organic solvent,
It is an object of the present invention to provide a silicone composition which is highly safe and does not pollute or destroy the environment and has good impregnation properties and coating properties.

[0005]

The present inventors have found that the above problem can be solved by using a low molecular weight methyl siloxane having a small surface tension and a low toxicity as a solvent.

That is, according to the present invention, (A) a vinyl group-containing diorganopolysiloxane having at least two CH ₂ ═CH—Si bonds in one molecule, (B) at least two in one molecule In the silicone composition containing an organohydrogenpolysiloxane having a hydrogen atom directly bonded to a silicon atom, (C) a platinum catalyst, and (D) a solvent, the solvent is represented by the formula (1):

[0007]

[Chemical 3] A low molecular weight linear methyl siloxane represented by the formula (2):

[0008]

[Chemical 4] There is provided a silicone composition characterized by being a low molecular weight methyl siloxane represented by or a mixture thereof.

The present invention will be described in more detail below. (A) Vinyl Group-Containing Organopolysiloxane The vinyl group-containing polysiloxane of the component (A) is usually linear, but may be slightly branched and may be used without any problem.

More specifically, the general formula (3):

[0011]

[Chemical 5] (In the formula, R ¹ is a substituted or unsubstituted monovalent hydrocarbon group containing no aliphatic unsaturated bond, p and q are 0 or a positive integer, preferably 0 <p + q ≦ 10000, more preferably Is 0 <p + q ≦ 2000, 0 <q / (p + q)
It is a preferable example. The substituent R ¹ in the formula (3) is a substituted or unsubstituted 1 to 10 carbon atom which does not contain an aliphatic unsaturated bond,
Particularly, it is preferably a monovalent hydrocarbon group having 1 to 6 carbon atoms, for example, a lower alkyl group such as methyl group, ethyl group, propyl group and butyl group; phenyl group, tolyl group, xylyl group, benzyl group and the like. Aryl group; cycloalkyl group such as cyclohexyl group, or chloromethyl group, cyanoethyl group, 3,3,3-trifluoropropyl group in which a part or all of hydrogen atoms of these groups are substituted with halogen atom, cyano group, etc. Is mentioned.

Despite the preferred example of the formula (3), the position of the vinyl group is not particularly limited and may be at the end of the polysiloxane main chain or at the middle thereof. Among them, a polysiloxane whose main chain is composed of polysiloxane and whose side chain has both a methyl group and a phenyl group as other groups is preferably used. Specific examples of such polysiloxanes include a homopolymer consisting only of methylphenylsiloxane units, a copolymer of dimethylsiloxane units and methylphenylsiloxane units, a copolymer of dimethylsiloxane units and diphenylsiloxane units, and the like. It

Further, vinyl group-containing polysiloxane (A)
Has a viscosity of 10 to 25 ° C. when used for impregnation.
It is preferably 400 cSt, especially 20 to 150 cSt. If the viscosity is less than 10 cSt, the resulting composition may easily volatilize after curing, and if it exceeds 400 cSt, the impregnating property of the composition may deteriorate. When it is used for forming a film, it is more than 400 cSt and 100,000 c
It is preferably St or less. If the viscosity is too low, the strength of the coating film obtained will decrease, and if it exceeds 100,000 cSt, workability such as mixing with other components will decrease.

Furthermore, the Na and Cl ion contents of the vinyl group-containing polysiloxane (A) are both preferably 10 ppm or less, more preferably 2 ppm or less. When the Na or Cl ion content is more than 10 ppm, the characteristics of electronic parts treated with this silicone composition may deteriorate. (B) Organohydrogenpolysiloxane As this organohydrogenpolysiloxane,
For example, the average composition formula _{(4): H a (R} 2) b SiO (4-ab) / 2 (4) ( wherein, R ² is a substituted or unsubstituted same or different free of aliphatic unsaturation Is a monovalent hydrocarbon group, a and b are represented by 0 <a <2, 1 ≦ b ≦ 2 and 2 ≦ a + b ≦ 3), and hydrogen bonded to silicon in one molecule. One having at least two atoms can be mentioned.

Here, R ² in the above formula (4) is a substituted or unsubstituted C 1 -C 1 containing no aliphatic unsaturated bond.
It is preferably 0, particularly a monovalent hydrocarbon group having 1 to 7 carbon atoms. Examples thereof include lower alkyl groups such as methyl group, aryl groups such as phenyl group, and the like as those described for R ^1. To be Also, a and b are 0 <a <2,
It is a number satisfying 1 ≦ b ≦ 2 and 2 ≦ a + b ≦ 3, preferably 0.3 ≦ a ≦ 1 and 2 ≦ a + b ≦ 2.7.

The position of the hydrogen atom bonded to silicon is not particularly limited, and it may be at the end of the molecule or in the middle thereof. Specifically, for example, methylhydrogenpolysiloxane having both ends trimethylsilyl group blocked, dimethylsiloxane / methylhydrogenpolysiloxane copolymer having both ends trimethylsilyl group blocked, methylhydrogenpolysiloxane having both ends dimethylhydrogensilyl group blocked. , A dimethylsiloxane-methylhydrogensiloxane copolymer having both ends dimethylhydrogensilyl group blocked,
Examples thereof include tetramethyltetrahydrogencyclotetrasiloxane, pentamethyltrihydrogencyclotetrasiloxane, tri (dimethylhydrogensiloxy) methylsilane and the like. In addition, this component may be linear, branched, cyclic, or network in terms of molecular structure.

The organohydrogenpolysiloxane preferably has a viscosity at 25 ° C. of 1 to 500 cSt, particularly 1 to 200 cSt. Viscosity is 1 cS
If less than t is used, the resulting composition is likely to volatilize after curing, and if more than 500 cSt, impregnation of the composition may deteriorate.

Such organohydrogenpolysiloxanes are usually R ² SiHCl ₂ , (R ² ) ₃ SiC.
_{^{l, (R 2) 2 SiCl}} 2, (R 2) 2 SiHCl ( wherein, R ² is as defined above) or hydrolyzing chlorosilanes such as, or obtained in this way by hydrolysis It can be obtained by equilibrating siloxane, and specific examples thereof include compounds represented by the following formula.

[0019]

[Chemical 6] Furthermore, N of organohydrogenpolysiloxane (B)
The a and Cl ion contents are both preferably 10 ppm or less, and particularly preferably 2 ppm or less. Content is 10p
If it is more than pm, the characteristics of the electronic component impregnated with this silicone composition are likely to deteriorate.

Organohydrogenpolysiloxane
The blending amount of (B) is generally 0.5 to 4 hydrogen atoms bonded to silicon in the component (B) with respect to one vinyl group in the vinyl group-containing polysiloxane of the component (A). The following range is preferable. Particularly, when the composition is used for impregnation, 0.5 to
The ratio is preferably 1.5, particularly 0.7 to 1.3. When used for forming a film, a range of 0.5 to 4, more preferably 1 to 4 is preferable. (C) Platinum-based catalyst This is for carrying out an addition reaction between the silicon-bonded vinyl group in the vinyl group-containing organopolysiloxane (A) and the silicon-bonded hydrogen atom in the organohydrogenpolysiloxane (B). A catalyst, which is usually used in this type of silicone rubber composition, can be used.

Examples of the platinum catalyst include platinum and a platinum compound. Specific examples include platinum alone, H ₂ PtCl ₆ .nH ₂ O, NaHPtCl ₆ .nH ₂
O, KHPtCl ₆ · nH ₂ O, Na ₂ PtCl ₆ · n
H ₂ O, K ₂ PtCl ₆ · nH ₂ O, PtCl ₄ · nH
Examples thereof include platinum compounds such as ₂ O, PtCl ₂ , Na ₂ PtCl ₄ .nH ₂ O and H ₂ PtCl ₄ .nH ₂ O, and complexes of these platinum compounds with hydrocarbon, alcohol or vinyl group-containing cyclic siloxane.

The amount of platinum catalyst (C) is the same as that of component (A) above.
Usually, 0.01% of platinum is added to the total amount of the component (B)
Is about 500 ppm, preferably 0.1 to 100 ppm. (D) Low-molecular-weight methyl siloxane This low-molecular-weight methyl siloxane has the general formula
The ones represented by (1) and (2) are used. These can be used alone or in combination of two or more.

Na and C in the low molecular weight methyl siloxane
l-ion content is 10 ppm or less, especially 2 pp
It is preferably m or less. When the Na and Cl ion contents are higher than 10 ppm, the characteristics of electronic parts treated with this silicone composition may deteriorate.

Since the low molecular weight methyl siloxane is used as a diluting solvent, the compounding amount varies depending on the purpose, but it is usually the same as or more than the total amount of the components (A), (B) and (C). It is preferable. Further, about 200 to 4000 parts by weight is preferable per 100 parts by weight of the total of the components (A) to (C).

The low molecular weight methyl siloxane has a low surface tension.
Therefore, the composition is provided with good impregnating property and coatability.
In addition, this low molecular weight methyl siloxane was produced in large quantities.
In terms of price, it should be similar to an industrial organic solvent.
There is also an advantage that you can. Other ingredients The composition may optionally contain other optional ingredients.
You can

The composition of the present invention can be prepared as a one-pack type or a two-pack type, but in the case of the one-pack type, it is usually preferable to add a curing reaction inhibitor. As the curing reaction inhibitor, for example, a polysiloxane containing a CH ₂ ═CHRSiO unit (wherein R represents a monovalent hydrocarbon group containing no aliphatic unsaturated double bond) (Japanese Patent Publication No. 48-10).
947), acetylene alcohol (for example,
An acetylene compound such as 3-methyl-1-butyn-3-ol) (see US Pat. No. 3,445,420) and the like are preferably used. The amount of the curing reaction inhibitor blended is 50 to 10,000 times (weight ratio) the platinum content of the platinum catalyst (C).
Is preferred. If it is too small, the composition may have poor storage stability and may be cured during long-term storage. If it is too large, the curing rate may be extremely slow.

As other optional components, for example, S added to reinforce the strength of the cured product.
iO ₂ unit, CH ₂ ═CH (R ′ ₂ ) SiO _0.5 unit,
R _'3 SiO _0.5 units (wherein, R' represents a monovalent hydrocarbon group containing no aliphatic unsaturated double bond) organopolysiloxane resin structure consisting of (Kokoku 38-2677
No. 1, 45-9476), heavy metal ionic compounds (see US Pat. No. 3,532,649), and the like. In addition, these additives can be added in an amount within a range that does not hinder the curing of the present invention.

When the composition of the present invention is used for impregnation, it is preferably prepared so that the content of solid impurities having a particle size of 5 μm or more is 1 mg / or less. When the content of solid impurities is large, it may be difficult for the composition to enter the fine gaps of the electronic component when used for impregnation. The solid impurities are mixed from the components (A) to (C) which are usually used as raw materials, but if such solid impurities are mixed, it is desirable to remove them by various methods. For example, the composition can be effectively removed by passing it through a Millipore filter having a gap of 8 to 0.1 μm.

When the composition is used for forming a thin film coating, the heat shrinkage at the time of curing is decreased, the thermal expansion coefficient of the cured product obtained by curing is decreased, the thermal stability, the weather resistance, the chemical resistance, A filler may be added for the purpose of improving flame retardancy or mechanical strength or reducing gas permeability, and examples thereof include fumed silica, quartz powder, titanium oxide and carbon black.

In addition, known alkoxysiloxanes, epoxy group-containing organopolysiloxanes, acryl group-containing organopolysiloxanes, etc. may be added to the base material for the purpose of improving the adhesion to the substrate. Uses The silicone composition of the present invention is an electronic component molded or sealed with a plastic package (epoxy resin, phenol resin, PPS resin, etc.) such as a transistor, a diode, an IC, a hybrid IC, a resistor, a capacitor, a chip capacitor, or a chip. Inductors, ceramics such as LC composite chip parts, electronic parts formed by sintering with an electrically insulating magnetic material (such as ferrite) are impregnated into the pores of the surface part of the electronic part, or by forming a coating on the surface. The electrical characteristics of the part are significantly improved.

When this silicone composition is used in electronic parts, it can be impregnated by an appropriate method. Examples of the impregnation method include a pressure impregnation method, a vacuum impregnation method, an atmospheric pressure impregnation method, and a surface coating method. Examples of the coating method include spray coating, dispenser coating and other commonly used methods.

The silicone composition of the present invention is cured after it is impregnated or applied to an electronic component, and the curing condition is usually such that it is cured at 80 to 150 ° C. for 0.5 to 3 hours. Can be adopted.

[0033]

EXAMPLES The present invention will be described with reference to examples. In the following description, parts indicate parts by weight, and the viscosity is a value measured at 25 ° C. Example 1 100 parts of dimethylpolysiloxane (100 cSt) containing 2 methylvinylsiloxane units in one molecule, S
Methylhydrogenpolysiloxane containing 0.5 mol / 100 g of iH bond 8.9 parts, octyl alcohol modified solution of chloroplatinic acid (platinum content 2% by weight) 0.02
Parts, acetylene alcohol (3-methyl-1-butyn-3-ol) 0.1 for the purpose of controlling the curing rate of the composition.
And 254.4 parts of hexamethyldisiloxane were mixed and stirred well, and then filtered through a Millipore filter having a 0.8 μm filter to obtain a silicone composition A. Comparative Example 1 Instead of 254.4 parts of hexamethyldisiloxane, dimethylpolysiloxane (viscosity: 10 cSt) was added at 254.
A silicone composition B was obtained in the same manner as in Example 1 except that 4 parts were compounded. Comparative Example 2 A silicone composition C was obtained in the same manner as in Example 1 except that 254.4 parts of an industrial reagent, primary toluene, was added instead of 254.4 parts of hexamethyldisiloxane. Comparative Example 3 A silicone composition D was obtained in the same manner as in Example 1 except that 254.4 parts of hexamethyldisiloxane was not added.

The diluents used in the silicone compositions of the above Examples and Comparative Examples 1 and 2 have the properties shown in the following table.

[0035]

[Table 1] Next, the moisture resistance of the above composition was evaluated by the following method.

Aluminum wiring (film thickness 1 μm, line width 5 μ
m) is mounted on a 14-pin Dip frame and then sealed with a thermosetting epoxy resin composition, the electronic component is sealed with a silicone composition by a normal pressure impregnation method and a reduced pressure vacuum impregnation method, respectively. Impregnated 15
It was cured at 0 ° C. for 1 hour and left in PCT (pressure cooker test, 121 ° C., 2 atm) for a predetermined time, and the open defect rate of aluminum wiring was measured.

The methods of normal pressure impregnation and reduced pressure vacuum impregnation are as follows.

Normal pressure impregnation: An electronic component is put in a container, and then an impregnating agent is added so that the component is completely immersed. After leaving for 30 minutes, the electronic component is taken out of the impregnating solution and excess drops are cut off. Remove and cure at 150 ° C / 1 hr.

Vacuum Impregnation: Electronic components are placed in a container, then an impregnating agent is added so that the components are completely immersed, the container is sealed in a desiccator, and suctioned by a vacuum pump through a methanol dry ice strap. Stop the vacuum pump after 30 minutes,
After returning to normal pressure to take out the electronic component and cut off the excess droplets, the impregnating agent adhering to the surface is removed and cured at 150 ° C./1 hr.

The results are shown in Tables 1 and 2.

[0041]

[Table 2]

[0042]

[Table 3] From the above results, it can be seen that the composition of Example 1 is excellent in impregnation property and is effective in shortening the process and improving the moisture resistance. Example 2 100 parts of dimethylpolysiloxane (1000 cSt) containing two methylvinylsiloxane units in one molecule,
1.4 parts of methylhydrogenpolysiloxane containing 1.0 mol / 100 g of ≡SiH bond, octyl alcohol modified solution of chloroplatinic acid (platinum content 2% by weight).
A composition was prepared by thoroughly stirring 05 parts and 3280 parts of hexamethyldisiloxane. 0.02 g of this was coated on a silicon wafer having a diameter of 4 inches at room temperature, air-dried for 10 minutes, and then heated at 150 ° C. for 1 hr to be cured. The shape, spread, and film thickness of the obtained coating were measured and evaluated. As for the shape, the coating vertical cross-sectional shape was measured by a surface roughness meter. Example 3 A composition was prepared, a coating was formed, and its evaluation was performed in the same manner as in Example 2 except that the amount of hexamethyldisiloxane used was changed to 1348 parts. Example 4 A composition was prepared, a coating was formed, and its evaluation was performed in the same manner as in Example 2 except that the amount of hexamethyldisiloxane used was changed to 405.8 parts. Example 5 A composition was prepared, a coating was formed, and its evaluation was performed in the same manner as in Example 2 except that 1348 parts of octamethylcyclotetrasiloxane was used instead of 3280 parts of hexamethyldisiloxane. Comparative Example 4 A composition was prepared, a coating was formed, and its evaluation was performed in the same manner as in Example 2 except that 1348 parts of the industrial reagent first-order normal heptane was used instead of 3280 parts of hexamethyldisiloxane. Comparative Example 5 A composition was prepared, a coating was formed and its evaluation was performed in the same manner as in Example 2 except that 1348 parts of the industrial reagent primary toluene was used instead of 3280 parts of hexamethyldisiloxane.

The results are shown in Table 4 and FIGS. 1 and 2.

[0044]

[Table 4] From the above results, the composition of the present invention as a thin film coating composition is superior in surface uniformity as compared with the conventional ones and is excellent in safety of volatile components generated during curing.

[0045]

EFFECTS OF THE INVENTION The silicone composition of the present invention does not use a conventionally used CFC-based solvent or organic solvent, is highly safe and does not pollute or destroy the environment, and has good impregnability. It has a thin film coating formability. As an impregnating agent or coating agent for electronic parts, the impregnating property and coating property are excellent, so that the impregnating method can be simplified and the impregnating time can be shortened, and the productivity is improved.

[Brief description of drawings]

FIG. 1 shows the vertical drawing shapes of the coating films obtained in Examples 2-5.

FIG. 2 shows the vertical drawing shapes of the coating films obtained in Comparative Examples 4 and 5.

Claims (2)

[Claims] 1. (A) At least two CH _{2 s in} one molecule.
A vinyl group-containing diorganopolysiloxane having a ═CH—Si bond, (B) an organohydrogenpolysiloxane having a hydrogen atom directly bonded to at least two silicon atoms in one molecule, (C) a platinum catalyst, and (D) ) In the silicone composition containing a solvent, the solvent has the formula (1)
: [Chemical 1] A low-molecular-weight linear methyl siloxane represented by the formula (2): A silicone composition characterized by being a low molecular weight methyl siloxane represented by or a mixture thereof. 2. The composition according to claim 1, wherein the amount of the solvent is 200 to 4000 parts by weight per 100 parts by weight of the total of the components (A), (B) and (C).