JPH02206667A - Powdery coating composition for sealing electrical and electronic part - Google Patents

Abstract

PURPOSE:To obtain the subject composition, consisting of a polyglycidyl ether of a polyfunctional phenol, linear phenolic resin, boron-based curing accelerator and inorganic filler, suitable as sealing materials for electrical parts and excellent in electrical characteristics, etc., under heated and moist conditions. CONSTITUTION:The objective composition consisting essentially of (A) a polyglycidyl ether of a polyfunctional phenol, (B) a linear phenolic resin having hydroxyl groups at both terminals with 2.0-4.0mequiv./g average phenolic hydroxyl group equiv., (C) a curing accelerator consisting of tetraphenylphosphonium tetraphenylborate and/or tetrabutylphosphonium tetraphenylborate and (D) an inorganic filler.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a powder coating composition for sealing electrical and electronic components, which is made of a powder composition mainly containing an epoxy resin. When used as a sealing material for capacitors, varistors, hybrid summer c, etc., it has excellent moisture resistance, heat resistance, and thermal shock resistance, and has particularly excellent electrical properties and storage stability in hot and humid conditions. The present invention provides a composition that can form an insulating coating layer having high physical properties.

[Prior Art] 7 Nipoxy resin powder compositions have been widely used as sealing materials for electrical and electronic components.

Epoxy resin powder compositions are relatively inexpensive, have excellent workability, and are highly reliable under various environments, which are the reasons why they are widely used.

On the other hand, in recent years, higher reliability has been required for electrical and electronic component sealing materials and other flexible materials as electronic components become more precise and the environments in which they are used expand. However, the reality is that conventionally used epoxy resin compositions cannot fully satisfy these requirements, particularly in terms of moisture resistance and thermal shock resistance.

Furthermore, when used in electrical and electronic components, it not only has excellent moisture resistance and heat resistance, but also has a good appearance of the insulating coating layer, and can be used to provide an insulating layer with a uniform thickness even for components with complex shapes. In particular, it is required to provide excellent coverage of the edge portions.

However, in order to satisfy both the good appearance of the insulation coating layer and the uniform coverage of the edges, the epoxy powder composition must have appropriate fluidity during coating, and the conventionally used epoxy When powder compositions are used for long-term coating, they may lose their proper fluidity, impair their appearance, make it impossible to obtain a uniform coating layer on the edges, and impair storage stability. At present, these requirements cannot be fully met.

[Problem to be solved by the invention]

In the insulating coating layer formed by curing the epoxy resin composition, the moisture resistance and thermal shock resistance are contradictory properties,
Improving moisture resistance by increasing the crosslinking density increases the stress at the interface between the cured product itself and the coated object, which reduces the thermal shock resistance of insulating parts and makes it difficult to obtain highly reliable properties. become unable. On the other hand, if the crosslinking density is lowered or a flexible component is added, the thermal shock resistance and edge coverage are excellent, but the heat resistance tends to be insufficient.9Also, even if these requirements are met, the When used for period painting,
It becomes impossible to satisfy any of the required characteristics, and storage stability deteriorates.

The inventors of the present invention have conducted extensive studies in order to obtain an insulating coating layer that can solve the above problems at once and has an excellent balance of properties such as moisture resistance, thermal shock resistance, edge coverage, and storage stability. As a result, when an insulating coating layer made of an epoxy resin powder coating composition made of a specific composition is applied to insulating parts, especially capacitors, blisters, hybrid ICs, etc., highly reliable characteristics can be obtained. The inventors have discovered that the required characteristics can be fully satisfied, and have completed the present invention.

[Means to solve the problem]

That is, the present invention provides (1) a polyglycidyl ether of a polyfunctional phenol, and (2) an average phenolic hydroxyl equivalent of 2.0 to 4.0 m.
eq/g, a linear phenolic resin having phenolic hydroxyl groups at both ends, (3) a curing accelerator consisting of at least one of tetraphenylphosphonium tetraphenylporate and tetrabutylphosphonium tetraphenylborate, and (4) an inorganic The present invention provides a composition containing the following fillers as a powder composition for sealing electrical and electronic components. This composition has excellent moisture resistance and thermal shock resistance, and can be used not only as a sealant but also as a general insulating material, an adhesive, etc. by taking advantage of its properties.

[Function and structure of the invention]

The polyglycidyl ether of polyfunctional phenol used in the present invention refers to a phenol glycidyl ether type epoxy resin containing on average 2.5 or more epoxy groups in one molecule, and in the present invention, the final product is a powder. Therefore, it is necessary to be solid at 30°C. Specific examples of polyglycidyl ethers of polyfunctional phenols include phenol novolac type epoxy resins, alkylphenol novolac type epoxy resins, and bisphenol A.
・Including novolac type epoxy resin, the following formula (I[)
Examples include epoxy resins represented by (IV).

(However, R" is H or CH:l.) Among these epoxy resins, cresol novolak type epoxy resins are particularly desirable from the viewpoint of the balance of moisture resistance, thermal shock resistance, and productivity.

In the present invention, these polyglycidyl ethers of polyfunctional phenols may be halogenated with a halogen such as bromine for the purpose of imparting flame retardance. At this time, the degree of halogenation is usually about 5% to 50% by weight.

In the present invention, epoxy resins other than the above-mentioned polyglycidyl ethers may be used, and other epoxy resins such as bisphenol A epoxy resins may be appropriately blended depending on the purpose. In this case, 5 of the total epoxy resin
It is desirable that the amount is 0% by weight or less, preferably 30% by weight or less.

Next, in the present invention, the linear phenolic resin having phenolic hydroxyl groups at both ends used as a curing agent for the epoxy resin has, on average, -1.8 or more phenolic hydroxyl groups in the molecule; A typical structure is a phenolic resin having phenolic hydroxyl groups at both ends, such as a compound such as formula (1), which is a reaction product of bisphenols and shrimp halohydrin (
(hereinafter referred to as the phenolic resin of the present invention).

...... (1) (However, R is H or CH, 3, n≧0) In the phenolic resin of the present invention, it is necessary to limit the hydroxyl equivalent, and the phenolic hydroxyl equivalent is 2.0 to 4. .0meq/
It is necessary that g. This is because this range is required as the length of the molecular chain between crosslinks, and it is 2.0 m.
When it is smaller than eq/g, the glass transition point decreases, resulting in a decrease in moisture resistance. On the other hand, 4. Omeq/g
If it exceeds this, thermal shock resistance will decrease. Furthermore (1)
In the compound, n=0, that is, bisphenol A or bisphenol F, must be contained in an amount of 30% by weight or less of the total. Even if the phenolic hydroxyl equivalent is within the above range, if bisphenol A or F is contained in an amount exceeding 30% by weight, foaming may occur during heat curing, resulting in a decrease in moisture resistance.

In addition, bisphenol A or bisphenol F in this case
It is difficult to directly measure the content of , and the weight % in this case is usually calculated from the peak area of GPC or liquid chromatography.

In the present invention, the blend ratio of the epoxy resin and the phenolic resin of the present invention is such that the phenolic hydroxyl group equivalent of the phenolic resin of the present invention is 0.2 to 1.0, preferably 0.5 to 1 equivalent of epoxy in the epoxy resin. ~1.0 equivalent. If the blending ratio of the phenolic resin of the present invention exceeds 1.0 equivalent, there is a disadvantage that moisture resistance and heat resistance decrease, and conversely, if it is less than 0.2 equivalent, the coating film becomes brittle and has poor impact resistance. The problem remains.

In the present invention, the softening point of the mixture obtained by blending the epoxy resin and the phenol resin of the present invention varies depending on each resin and blend ratio, but is usually 40 to 12
0°C, and it was found that in that case, there would be no adverse effects such as a decrease in impact resistance due to the improvement in heat resistance.

The curing accelerator used in the present invention is tetraphenylhomphonium tetraphenylborate or (and) tetrabutylphosphonium tetraphenylporate, and must be used. Compared to other tertiary amines, imidazoles, or special amines that are commonly used as curing accelerators, it has excellent moisture resistance especially at high temperatures, so it is significantly more reliable when used as an insulating coating for electrical and electronic components. improve. The curing accelerator of the present invention has excellent moisture resistance reliability, so it is superior to triphenylphosphine (hereinafter referred to as TPP), which is often used as a curing accelerator for electrical and electronic component sealing materials. This accelerator has better moisture resistance reliability.

In other words, the electrical insulation properties after moisture absorption are superior between the two, but
Even in PCBT (Pressure Cutler Bias Test), which is conducted by applying current even during moisture absorption, when the curing accelerator of the present invention is used, compared to TPP, the decrease in electrical insulation properties is extremely small, making it suitable for soil-based electrical and electronic components. Suitable as a material, especially for capacitors, varistors, hybrid I
When applied to C, etc., it exhibits highly reliable characteristics.

In addition, in terms of storage stability, compared to TPP, when the above-mentioned curing accelerator of the present invention is used, there is little deterioration in properties in terms of coating appearance and uniform coating properties at edges after long-term storage, and it is extremely stable. Because of this, we can expect a significant improvement in coating workability, which can greatly contribute to improving quality stability and reliability.

The amount used varies depending on the purpose and use, but it is usually preferably 0.01 to 5 parts by weight per 100 parts by weight of the epoxy resin.

The inorganic filler used in the present invention has a lower coefficient of linear expansion,
It works to improve heat dissipation, mechanical strength, and edge coverage, such as silica, alumina, calcium carbonate, titanium oxide, zirconia, talc, barium sulfate, calcium silicate, and Inorganic powder such as magnesium is used. Further, for applications requiring flame retardancy, it is preferable to use a flame retardant filler such as antimony trioxide. The amount of these added is epoxy resin 10
The amount is 2 to 500 parts by weight relative to 0 parts by weight.

In addition to these essential ingredients, various additives can be added depending on the purpose as long as they do not reduce moisture resistance and thermal shock resistance, such as silane coupling agents, titanium coupling agents, surface conditioning agents, etc. Examples include pigments.

Epoxy powder compositions made of such components are usually prepared by dry mixing the components, thoroughly melting and mixing them using a two-roll, -shaft, or twin-shaft kneader, and then pulverizing and classifying them. It can be obtained by doing .

The obtained powder composition can be coated on electrical and electronic parts such as capacitors, varistors, and hybrid ICs by, for example, fluid dipping, spraying, electrostatic spraying, sprinkling, etc.
The desired article can be obtained by forming an insulating coating layer by a known method such as an injection molding method or an electrostatic dynamic dipping method, and heating and curing the layer.

〔Effect of the invention〕

As described above, since the coating composition of the present invention is an epoxy resin powder composition having a specific composition, it can be applied to electrical and electronic components, particularly capacitors, varistors, hybrid ICs, etc. It has excellent moisture resistance and reliability compared to other products, and also has well-balanced properties such as heat resistance, thermal shock resistance, surface smoothness, improved uniformity of coating thickness at edges, and storage stability. Then,
The electrical and electronic components have high reliability in the properties obtained without causing defects in the properties that they should originally exhibit.

〔Example〕

Examples of the present invention will be shown below and will be explained more specifically.

Examples 1 to 5 Each component shown in Table 1 was heated and melted, mixed, cooled, and then ground.
The mixture was classified to obtain an epoxy resin powder coating composition, and the resulting composition was subjected to fluid dip coating at a preheating temperature of 150°C to obtain insulating parts. Varistor voltage 220 as the object to be coated
■ A ceramic varistor was used. The resulting insulating coating layer had an average thickness of about 500 μm.

Comparative Examples 1 to 4 Each component shown in Table 1 was coated on an object in the same manner as in the example to obtain an insulating part.

The characteristics of the insulating parts (varistors) obtained in each of the above Examples and Comparative Examples were evaluated, and the results are shown in Table 1.

It should be noted that the component blending ratios in Table 1 each indicate parts by weight. In addition, the measurement methods for moisture resistance 1, moisture resistance 2, insulating layer uniformity, thermal shock resistance, and storage stability in the same table are as follows.

(1) “Konrei Nami”.

It was left for 100 hours in saturated water vapor at 12 biC and 12 atmospheres, and the voltage before and after the time when the leakage current reached 10μ was measured, and the rate of voltage change was calculated using the following formula. (n=3
0). However, when n=30, the number of identical test samples is 3.
Indicates that there are 0 pieces. same as below.

■o - initial voltage■,. . h, = Voltage after being left for 100 hours (2) 1
A DC voltage of 30V was applied between the element electrodes of the object to be coated in an atmosphere of 130'C185%RH and left for 100 hours.
The voltage when the leakage current reached 10μ before and after being left was measured, and the rate of voltage change was calculated based on the humidity resistance 1 and the voltage difference. (
n, = 30) (3) Insulating layer uniformity After cutting the object to be coated with a fine cutter, it was cut under a microscope (100
Observation was made at (n=5) (4) Thermal shock resistance - One cycle consists of cooling at 40°C for 5 minutes and then heating at 125°C for 5 minutes (liquid layer type) heating conditions: 2
After 50 cycles, the number of cracks generated after that was examined. (n=30) (5) Storage stability After leaving the obtained powder composition in an atmosphere of 35°C and 50RH% for 1000 hours, it was coated on the object to be coated under the above conditions to improve its appearance and insulation. The layer uniformity was investigated. (n=5)

Claims (1)

[Claims] 1. (1) polyglycidyl ether of polyfunctional phenol; (2) average phenolic hydroxyl equivalent of 2.0 to 4.0 m
eq/g, a linear phenolic resin having phenolic hydroxyl groups at both ends, (3) a curing accelerator consisting of at least one of tetraphenylphosphonium tetraphenylborate and tetrabutylphosphonium tetraphenylborate, and (4) an inorganic A powder coating composition for sealing electrical and electronic components, which contains a filler and the like as essential components. 2. The above-mentioned linear phenol resin having phenolic hydroxyl groups at both ends is a linear phenol resin represented by the following formula (I) obtained from bisphenol A or (and) bisphenol F and an epihalohydrin, and is represented by the formula ( 2. The powder coating composition for sealing electrical and electronic components according to claim 1, wherein the weight percent of n=0 (i.e., bisphenol A or/and bisphenol F) in I) is 30% or less. ▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・・・・(I) (However, R indicates the same or different H or CH_3, and n≧0)