JP2740005B2 - Resin composition for impregnation - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an impregnating agent for improving the moisture resistance of a resin material coated on an electronic / electric part.

[Conventional technology]

Various waxes such as paraffin have been conventionally used as such an impregnating agent.

This wax is usually a low melting solid, but
It is melted by heating at about 80 ° C to make it a low-viscosity liquid and is subjected to impregnation.

Of these waxes, microcrystalline ones have good electric properties, a relatively high melting point of 80 to 90 ° C., excellent moisture resistance, and good impregnation workability.

However, since wax is inherently thermoplastic, if the product after the impregnation treatment is heated to a temperature higher than the melting point of the wax, the wax is eluted and the moisture-proof effect intended for the impregnation use is lost.

In recent years, the need for increasing the reliability of electronic components has increased, and the specification of the maximum operating temperature of products has also increased from 60 to 80 ° C to 100 to 120 ° C.

In order to cope with this, a wax material having a high melting point of 120 ° C. or more may be applied, but the melt viscosity at the time of heating and impregnation becomes extremely high, and the impregnation workability is greatly reduced.

In addition, wax is generally flammable, and it is difficult to apply it to electric and electronic parts that require high flame retardancy.

The production of flame-retardant wax is described in JP-B-53-5440.
However, such a wax is unsatisfactory in that it ignites even when ignited, causing a drop and promoting the spread of combustion.

Further, if the solvent is washed with freon or the like, since the solvent resistance of the wax is not good, the impregnated surface is whitened, and troubles such as inability to print the product are likely to occur.

On the other hand, non-solvent type liquid resins such as epoxy resin and urethane resin have many high viscosity ones, impregnation work efficiency is low, and the curing stress of the resin at the time of curing is strong,
Practical use is difficult because the characteristics of parts may be impaired.

The present inventors have studied the application of various resins in order to solve the items that had been problematic in terms of moisture resistance at high temperatures, solvent resistance, and flame retardancy in the conventional wax-based impregnating agent, As shown in JP-A-63-168457, certain silicone resins have low viscosity and good impregnating properties, and have an appropriate curing property and preservability by combining an appropriate curing agent, and also have a moisture resistance required as an impregnating agent. It has been found that the material has good resistance, solvent resistance and flame retardancy.

However, although this type of silicone resin cures quickly, it has high reactivity under moisture absorption, reacts with moisture in the air, polymerizes on the liquid surface, and is liable to cause a film sticking phenomenon.

[Problems to be solved by the invention]

As a result of intensive research on combinations of various silicone resins and curing agents in order to develop excellent properties as an impregnating agent, quick curing, and excellent pot life, the specific silicone resin represented by the following structural formula It has been found that a combination of one or more organometallic salt compounds can achieve both curability and storability (pot life), thereby completing the present invention.

[Means for solving the problem]

The present invention provides an organic acid metal salt compound in the silicone resin of the structural formula (I), based on 100 parts by weight of the silicone resin.
0.01-1.0 parts by weight, viscosity 0.05-0.5 poise / 25
The present invention relates to a resin composition for impregnation at a temperature of ° C.

_{(R 1, R 2, R} 3, R 4, R 5, R 6: CH 3, C 2 H 5, R 7: H, CH 3, C 2 H
₅ , R ₈ : CH ₃ , C ₂ H _{5 wherein} n R ₇ and R ₈ may be the same or different, and two or more R ₇ are H.
The silicone resin used in the present invention is of a condensation reaction type which cures at a temperature of 100 ° C. or higher in a relatively short time when a curing agent is blended with a low viscosity.

A silicone resin having a phenyl group introduced into the side chain of a silicone resin has a high viscosity and cannot be impregnated into the inside of the coating film in a short time.

On the other hand, the type having extremely low molecular weight and low viscosity has high volatility and is easily volatilized at the time of heating in the impregnation process, and the cured coating film is fragile, which is not suitable.

The silicone resin in the present invention has a hydrogen group on the side chain of the polymerization repeating unit, and has an appropriate degree of polymerization (n) of 10 to 100, and therefore has low viscosity and good curability.

On the other hand, those having a hydroxyl group at the terminal have high reactivity under moisture absorption and have poor storage stability.

Therefore, in terms of impregnation workability, curability, strength, etc., the silicone resin represented by the structural formula [I] has a viscosity of 5 to 50 cp.
Those having a molecular weight of / 25 ° C. level are preferred.

It is necessary to mix one or more curing agents of the organic acid metal salt compound with this compound [I] and mix it in an appropriate amount. The total amount of the catalyst is 0.01 to 1 PHR.

 Next, the organic acid metal salt will be described.

As the metal, various metals such as lead, tin, zinc, cobalt, manganese, chromium, zirconium, and titanium are effective. In particular, tin and zinc have excellent action effects. However, the combination is more preferable. There are various organic acids such as acetic acid, maleic acid, succinic acid, oleic acid, stearic acid, lauric acid and the like, and although there are slight differences in the effects, they are not particularly limited.

It is preferable to use two or more different curing agents in combination. In the case of two kinds such as zinc and tin, the combination ratio is appropriately 1/4 to 4/1 in equivalent ratio.

Furthermore, as in the case of mixing other metal salts with zinc and lead,
Even when three or more kinds are used in combination, it is preferable that each component is blended in an equivalent ratio of 20% or more.

Although the reason for the compatibility between preservability and curability by this combination is not clear, there is a point that the catalytic effect of each metal is slightly different. It is presumed that, when a plurality of the compounds are blended, the respective metal salts complement each other, so that the curability is improved while maintaining the storage stability. Each metal salt is effective in combination depending on the combination, but as described above, the combination of zinc salt and tin salt is most effective.

Note that the storage stability (pot life) greatly depends on the total addition amount of the catalyst, and therefore, is ensured by keeping the addition amount at 1 PHR or less. The effect of addition is small at 0.01 PHR or less.

An electronic / electric component covered with a dip coating is impregnated with the impregnating agent according to the present invention and cured by heat. The component has appropriate flexibility and adhesion, and exhibits excellent moisture-proof curing.

Since the coating film is rich in flexibility, there is no concern that the properties of the element may be changed due to a large curing stress observed when another thermosetting resin such as an epoxy resin or a urethane resin is applied to the impregnating agent.

〔Example〕

A silicone resin represented by the following structural formula conforming to the present invention was prepared.

The silicone resin was blended with a predetermined amount of various curing agents shown in Table 1 to prepare an impregnating agent.

In addition, a ceramic substrate with lead terminals (size
Dip paint PR-53365 to 40mm, width 20mm, thickness 0.65mm)
(Manufactured by Sumitomo Bakelite) twice, air-dried at 150 ℃, 6
After baking for 0 minutes, a cured coating film having a thickness of about 0.7 mm was obtained.

The impregnating property of the inside of the coating film when this cured product was immersed in various impregnating agents (heated to 80 ° C.) shown in Table 1 was evaluated. The impregnating property was evaluated by pulling a sample after impregnation, cutting the sample, and determining whether the coating was impregnated.

Next, using the sample after the impregnation treatment, the curability, the solvent resistance after curing, and the flame retardancy were further evaluated.

The storage stability was measured by keeping the impregnating liquid at 80 ° C. and measuring the change in viscosity with a B-type rotational viscometer.

 The measuring method of curability and the like is as follows.

Curability: The surface tackiness of the sample after impregnation at the time of heat treatment at 150 ° C is examined to determine the tack-free time.

Solvent resistance: After immersion in a Freon liquid at 40 ° C. for 10 minutes, the surface condition of the coating film is observed.

Flame retardancy: Observe the presence or absence of ignition when in contact with a 10mm burner flame for 10 seconds.

[Effect of the Invention] The impregnating resin composition of the present invention is thermosetting and has excellent moisture resistance, heat resistance, solvent resistance and moderate flame retardancy. The above-mentioned characteristic items, which have been regarded as disadvantages of the above, are all improved at once, and are suitable as impregnating agents applied to electronic / electric parts requiring high reliability.

Further, since the curing after the impregnation is fast, the firing time in the actual process can be shortened, which is also useful in improving the productivity.

Claims (1)

(57) [Claims] Claims: 1. An organic acid metal salt compound is added to a silicone resin of the structural formula [I] based on 100 parts by weight of the silicone resin.
0.01-1.0 parts by weight, viscosity 0.05-0.5 poise / 25
A resin composition for impregnation at a temperature of ° C. _{(R 1, R 2, R} 3, R 4, R 5, R 6: CH 3, C 2 H 5, R 7: H, CH 3, C 2 H
₅ , R ₈ : CH ₃ , C ₂ H _{5 wherein} n R ₇ and R ₈ may be the same or different, and two or more R ₇ are H.
n = 10-100)