JPH06220367A - Electrical insulating coating composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition, comprising a specific thermosetting resin, a filler, a specified thixotropic agent and an additive, capable of remarkably improving the moisture resistance and denseness while maintaining excellent dipping operating efficiency, etc., and responsive to a wax impregnation-less method. CONSTITUTION:This coating composition comprises (A) a thermosetting resin consisting essentially of a dimethylene ether type phenolic resin or this resin and an epoxy resin, (B) a filler, (C) a thixotropic agent containing an organic bentonite as a principal component and (D) an additive as essential components. The dimethylene ether type phenolic resin which is the component (A) is preferably obtained by subjecting phenols and formaldehyde at 1:(1.2-2.5) molar ratio to condensing reaction in the presence of a bivalent metallic salt catalyst such as zinc acetate under refluxing conditions for 4-8hr and then dehydrating the resultant product at 120 deg.C under reduced pressure. Furthermore, a bisphenol A type, etc., are preferred as the epoxy resin which is the component (A). A silane coupling agent, etc., are preferably used as the component (D) in order to further improve the adhesion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulating coating material for electronic parts, particularly an exterior coating material for forming a protective coating for electrical insulation on various capacitors, varistors, hybrid ICs and the like.

[0002]

2. Description of the Related Art Electronic parts are coated with an insulating coating for the purpose of protection from moisture and mechanical protection. The characteristics of this insulating paint directly affect the moisture resistance and mechanical characteristics of electronic components. On the other hand, as a coating method for electronic parts, there are a solvent-based dip coating method, a casting method, a powder coating method, a molding method and the like. Among them, the solvent-based dip coating method is a method of dipping and coating an electronic component with a paint prepared by blending a solvent with a composition comprising a thermosetting resin, a filler, a thixotropic agent, an additive, etc., and partially drying the solvent by air drying. This is a method of coating the electronic component by evaporating it and then heat-curing it. When high humidity resistance is required, a method of impregnating these electronic parts with wax or silicone is adopted.

Since the material used in the solvent-based dip coating method contains a large amount of filler, the cured coating film is generally porous and has a small coefficient of thermal expansion and excellent thermal shock resistance. Particularly in the field of hybrid IC, as a chip coating material for partially covering a semiconductor chip or the like as a resin sealing material, and as an exterior material for covering a circuit board on which a molded component or the like is mounted,
Since the solvent-based coating material has excellent thermal shock resistance characteristics as described above, its use is increasing.

In recent years, the required performance of electronic parts has become strict,
It is desired to develop a dense material having a higher moisture resistance level even in the wax impregnation-less system in which the wax impregnation treatment in which the working process is complicated is performed while maintaining the thermal shock resistance of the solvent-based coating material. Further, when attempting to achieve this densification, there are problems such as sagging of the paint during dipping work, sagging during heat curing, and blistering unless air drying is performed sufficiently. In particular, controlling the fluidity of the paint during heating has been a difficult problem.

[0005]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention As a result of research to improve the moisture resistance level of solvent-based dip coating materials, which are generally insufficient in moisture resistance, the present inventor has revealed that the moisture resistance is dense and greatly improved, and The inventors have found a structure that can solve various problems such as sagging property and filler sedimentation property, and have completed the present invention. The object of the present invention is a high solid type that can improve the compactness and moisture resistance significantly while maintaining the original functions such as dipping workability and thermal shock resistance of the solvent-based coating material, and can also support the wax impregnation-less method. The present invention provides a coating composition.

[0006]

According to the present invention, the essential components are
A coating composition for electrical insulation comprising a thermosetting resin, a filler, a thixotropic agent and an additive, wherein the thermosetting resin component is a dimethylene ether type phenol resin as a main component, or an epoxy resin. The composition for electrical insulation coating is characterized in that the main component of the thixotropic agent is organic bentonite.

The dimethylene ether type phenol resin used in the present invention has a molar ratio of phenols to formaldehydes of 1: 1.0 to 3.0 in the presence of a divalent metal salt.
It is preferably a viscous or solid resin obtained by condensation reaction under reflux at 1: 1.2 to 2.5 for 4 to 8 hours and then dehydration under reduced pressure at 120 ° C. The resin thus obtained is 11
It is a resin that hardly hardens at temperatures below 0 ° C.
It has a structure having a methylol group, a methylene group, and a dimethylene ether group. The dimethylene ether type phenol resin used in the present invention is preferably the dimethylene ether bond, the methylene bond, and the moles of the dimethylene ether bond in the sum of the number of moles of the methylol group from the result of the NMR analysis after acetylation. Number ratio is 15 ~
40%, the number average molecular weight is 300 to 600, and the unreacted phenol content is 3.5% or less.

The phenols used in the present invention are
Bifunctional phenols include orthocresol, paracresol, paraethylphenol, parapropylphenol,
Paratertiary butylphenol, paraoctylphenol, paranonylphenol, paraphenylphenol and the like, and trifunctional or higher functional phenols include phenol, metacresol, 3,5-xylenol, resorcinol, catechol, bisphenol A and bisphenol F. , Or one or more selected from these. Formaldehyde is formaldehyde, paraformaldehyde, trioxane, or the like, and they can be used in combination.

The organic acid metal salt used as the reaction catalyst is one or more selected from divalent metal salts of organic acid, and the organic acid is carboxylic acid, naphthenic acid, sulfonic acid, and sulfinic acid. Among them, carboxylic acid and naphthenic acid are particularly preferable, and as divalent metal types, there are lead, calcium, manganese, tin, zinc, copper, magnesium, barium and the like, but lead, manganese, zinc and barium are particularly preferable. preferable. In addition, a small amount of an acid catalyst such as hydrochloric acid, oxalic acid, or paratoluenesulfonic acid, or a basic catalyst such as calcium hydroxide, ammonia, or triethylamine can be used together. The amount of the catalyst used when the phenols and the formaldehydes are reacted under weak acidity with the organic acid metal salt as a catalyst is usually 0.0 with respect to 1 mol of the phenols.
Phenols and formaldehydes are reacted so that the pH of the reaction system is 005 to 0.01 mol, preferably 4.5 to 6.0.

The epoxy resin used in the present invention is
Those having at least two epoxy groups in one molecule, and bisphenol A type epoxy resin, bisphenol F type epoxy resin, aliphatic glycidyl ether type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, alicyclic Formula epoxy resins, brominated epoxy resins, various modified epoxy resins, and the like, and some of them can be used in combination. Bisphenol A type or bisphenol F type epoxy resin is preferable, and it is possible to improve the thermal shock resistance and moisture resistance in a well-balanced manner. By blending an epoxy resin as the thermosetting resin component of the present invention, it is possible to further improve the adhesion to the element or the substrate and the impact resistance.

When the thermosetting resin component is a dimethylene ether type phenol resin, 30 to 50% of a novolac type phenol resin is blended in addition to being used alone to improve the strength and reduce the volatile content during curing. The densification can be improved. When the thermosetting resin component is a combination of a dimethylene ether type phenolic resin and an epoxy resin, the compounding is 20 to 60 dimethylene ether type phenolic resin.
%, The epoxy resin 80 to 40% is preferable, and when the dimethylene ether type phenol resin is 20% or less, the curability becomes slow, and it is necessary to supplement the addition of a curing accelerator for the epoxy resin. Further, the blending amount of the thermosetting resin component with respect to the entire solid content is preferably 15 to 35%.

The filler used in the present invention is a crushed or spherical inorganic filler such as calcium carbonate, alumina, talc, crystalline silica, fused silica, and sintered aluminum silicate, but is not limited thereto. Alternatively, one or more of these fillers can be used in combination. Also, a filler treated with a coupling agent may be used. The thixotropic agent used in the present invention uses an organic bentonite type (amine-bonded bentonite complex) thixotropic agent as a main component, and can improve sag and sedimentation properties and soft cake formation of sediments. Solvents used in the present invention include hydrocarbon solvents such as toluene and xylene, alcohol solvents such as ethyl alcohol, ketone solvents such as acetone and methyl ethyl ketone, and others, ester-based, ether-based, ether alcohol-based, ether ester-based solvents. 1 type, or 2 or more types of solvents are used. As for additives, silane coupling agents and titanate coupling agents are added to the filler to improve the adhesion.
It is preferable to contain 1 to 2.0% by weight. Other additives include imidazole and its cyanoethylated adducts and aromatic amines, organic phosphines such as triphenylphosphine, hydrazines, curing accelerators, leveling agents, defoaming agents, pigments, dyes, An appropriate amount of a flame retardant aid such as antimony trioxide can be blended.

[0013]

The composition for electrical insulation coating of the present invention can greatly improve the compactness and the moisture resistance as compared with the conventional resole-type phenol resin and the composition comprising the resole-type phenol resin and the epoxy resin. it can. Therefore, conventionally, the field in which high reliability is required has been dealt with by impregnation with wax, but the composition of the present invention can provide a sufficiently reliable outer packaged product even without the wax impregnation method.
This is when curing the dimethylene ether type phenolic resin,
It is considered that the fact that the amount of volatile components such as condensed water generated at the time of reaction curing with the epoxy resin effectively reduces the denseness. In addition to this, it is excellent in the dip workability such as the storage stability of the paste, the stability of sedimentation, the sagging property, and particularly the sagging property when heated. Further, in the conventional dip coat resin, defects such as blister of the coating film are generated unless the coating step is air-dried for 3 to 6 hours, whereas the composition of the present invention contains the dimethylene ether type phenol resin at 110%. Almost no reaction occurs at temperatures below ℃.
Since the solvent evaporation operation can be performed at 0 to 100 ° C., the air drying operation can be omitted and the drying and curing step can be shortened.

[0014]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited to the examples.
"Parts" and "%" described in the examples and comparative examples
Indicates "parts by weight" and "% by weight". << Production Example 1 >> 150 parts of phenol, 850 parts of para-cresol in a reactor equipped with a stirrer, a reflux condenser and a thermometer,
Charge 583 parts of 80% paraformaldehyde, charge 5 parts of manganese acetate, and gradually raise the temperature to 110 ° C.
After reaching, the reaction was carried out under reflux for 5 hours. Then 40 Torr
The dehydration reaction was performed under reduced pressure, and when the internal temperature reached 122 ° C., the dehydration reaction was terminated to obtain a resin. Then, methyl ethyl ketone was added and mixed to obtain a dimethylene ether type phenol resin (A) having a nonvolatile content of 65%.

<Production Example 2> Phenol 9 was added to the reactor.
40 parts, 490 parts of 80% paraformaldehyde and 4 parts of zinc acetate were charged and the reflux reaction and the dehydration reaction were carried out in the same manner as in Example 1 to obtain a solid dimethylene ether type phenol resin (B) having a melting point of 65 ° C. It was <Production Example 3> 940 parts of phenol, 37% formalin 5
Introduce 00 parts and 10 parts of oxalic acid, carry out the reaction at a temperature of 100 ° C. for 2 hours, perform a vacuum dehydration reaction, and a melting point of 72 ° C.
Novolak type phenolic resin was obtained. <Production Example 4> 940 parts of phenol, 37% formalin 1
460 parts, 20 parts of 28% ammonia were charged, and the temperature was 10
After reacting at 0 ° C. for 40 minutes and performing vacuum dehydration reaction, methyl ethyl ketone was added and mixed at an internal temperature of 95 ° C. to obtain a resole-type phenol resin having a nonvolatile content of 65%.

<< Examples 1 to 3, Comparative Examples 1 to 3 >> A paste was prepared by dissolving and mixing for 4 hours in a mixing machine at a blending ratio shown in Table 1 and further diluted with methyl ethyl ketone at 25 ° C.
The viscosity was adjusted to 20 poise and an evaluation test was conducted. The evaluation results are shown in Table 1.

The evaluation method was as follows. 1. Sedimentability 100 ml of paste was placed in a 100 ml graduated cylinder and allowed to stand to measure the separation start time of the supernatant (unit: hour), whereby the sedimentation stability of the paste was evaluated. 2. After adjusting the hardness of the sediment, a glass rod was inserted into the paste left at room temperature for one month, and the hardness of the sediment was observed. 3. Coating characteristics Dip coating is performed by immersing the alumina ceramic substrate in the lengthwise direction only about half, and then air-drying at room temperature for 1 hour.
Treat at 0 ° C for 30 minutes, 110 ° C for 30 minutes, then 15
The coating film obtained was baked and cured at 0 ° C. for 2 hours, and the appearance of the coating film was observed to evaluate the hot sagging property and the smoothness and denseness of the coating film as described below. (1) Sagging property when heated The degree of sagging of the coating film was visually observed, and those without sagging were indicated as ◯, and those with sagging were indicated as x. (2) Smoothness and denseness of coating film The smoothness (whether there are blisters and pinholes) and the degree of denseness were observed by a red check.

4. Moisture resistance (1) Fabrication of evaluation element Circuit width 0.3c with Ag / Pd paste on alumina substrate
m, comb resistance of 0.3 cm between circuits is baked, and a test pattern with lead frame attached is dip-coated with the above paste, air-dried at room temperature for 1 hour, and then treated at 90 ° C for 30 minutes and 110 ° C for 30 minutes. It was baked and cured at 150 ° C. for 2 hours to prepare an evaluation element having a film thickness of 0.3 mm. (2) Evaluation method The evaluation element was treated with a pressure cooker (121 ° C., 2 atm) for 200 hours, left at room temperature for 1 hour, and then the insulation resistance between circuits was measured. The number of circuit defects / total number of patterns is displayed as a defect of 10 ⁷ Ω or less (initial value of 10 ¹⁴ Ω or more).

[0019]

[Table 1]

[0020]

EFFECT OF THE INVENTION The composition for electrical insulation coating of the present invention greatly improves the compactness and moisture resistance as compared with the composition using the conventional resol type phenol resin. Therefore, the wax impregnation-less method can be adopted even in a field requiring high reliability. In addition to this, it is excellent in the dip workability such as the storage stability of the paste, the stability of sedimentation, the sagging property, and particularly the sagging property when heated. Further, the conventional dip coat resin required an air drying operation in the coating process, but in the composition of the present invention,
Air drying can be omitted, and the drying and curing process can be shortened.

Claims (1)

[Claims] 1. An electrically insulating coating composition comprising a thermosetting resin, a filler, a thixotropic agent and an additive as an essential component, the thermosetting resin component having a dimethylene ether type phenol as a main component. A resin or an epoxy resin and a thixotropic agent main component is organic bentonite, which is a composition for electrical insulation coating.