JPH04146980A - Coating composition for electronic part - Google Patents

Abstract

PURPOSE:To improve the solder resistance, insulation resistance, moisture resistance, heat resistance and durability of a cured coating film and storage stability as a one-pack type by compounding an epoxy resin, a specified dihydrazide compd. and an inorg. extender pigment. CONSTITUTION:The title compsn. is obtd. by compounding 100 pts.wt. epoxy resin which is pref. a bisphenol A type epoxy resin and/or a cresol novolak type epoxy resin, 10-60 pts.wt. dihydrazide compd. contg. 70wt.% or more aliph. dihydrazide compd. of the formula (wherein n is 8-10) which is a curing agent for the epoxy resin, 60-150 pts.wt. inorg. extender pigment consisting of an inorg. filler and, if necessary, a coloring pigment, an anti-sag agent, a (non)- reactive diluent, a flame-retardant, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a coating composition suitable for the insulation and moisture-proof protection of electronic components.

[Conventional technology]

Epoxy resin has excellent electrical insulation, moisture resistance, mechanical and thermal properties, and is used for insulation and moisture-proof protection of various electronic components such as fixed resistors that have a carbon film or metal film on the surface as a resistor. It is widely used as

When using an epoxy resin for this type of application, a method is used in which the epoxy resin and an appropriate curing agent are combined and cured. Examples of curing agents used here include polyamines, acid anhydrides, phenols, Imidazole, dicyandiamide, amine complex of fluorine trifluoride, dihydrazide, etc. are known.

However, when polyamines, acid anhydrides, and phenols are mixed with epoxy resins, curing reactions proceed even at room temperature, which limits their pot life. For this reason, in reality, it is necessary to store the epoxy resin and the curing agent in separate containers, and to handle them as a two-component type, by mixing only the required amounts of both immediately before use, which is cumbersome and difficult to handle. The remainder of the mixture becomes gelled and becomes unusable, which is economically disadvantageous.

On the other hand, imidazole, dicyandiamide, amine complexes of fluorine trifluoride, and dihydrazide do not have the above-mentioned drawbacks and can be adequately handled as a -liquid coating material.

However, among these curing agents, imidazole and dicyandiamide have the disadvantage that the cured coating film has poor moisture resistance, and the amine complex of boron trifluoride generates amine gas during heat curing, causing discoloration of the coating film.

For this reason, dihydrazide is currently being used as the most suitable curing agent that can be handled as a liquid paint and does not have the above-mentioned problems such as moisture resistance and discoloration. As such dihydrazide, Japanese Patent Application Laid-Open No. 60-127702
The publication discloses aromatic dicarboxylic acid dihydrazide, 2,4-dihydrazine-6-alkylaminotriazine having a heterocycle, and the like.

[Problem to be solved by the invention]

However, although the above-mentioned known dihydrazides have the above-mentioned advantages, the cured coating film is inferior in solder resistance, and cracks occur in the cured coating film after being immersed in a solder bath, causing electronic components to be damaged by the fixed resistor. In this case, there was a problem in that the resistance value greatly increased due to the occurrence of the above-mentioned cracks.

The present invention provides a coating composition for electronic components that overcomes the problems of the prior art and also satisfies various other properties that have been strictly required in recent years, especially for home appliances and electronic devices. It is intended to.

That is, the object of the present invention is to develop an epoxy resin that has excellent solder resistance in a cured coating film, and also satisfies the properties inherent in the coating film, such as insulation resistance, moisture resistance, heat resistance, and durability (cold/thermal cycling resistance). An object of the present invention is to provide a coating composition for electronic parts which is a resin composition, which has good storage stability as a one-component type, and which can be rapidly cured at a predetermined heating temperature when curing. .

[Means to solve the problem]

As a result of extensive research to achieve the above object, the present inventors have found that when a specific aliphatic dihydrazide compound is used as a curing agent for epoxy resin, an electronic It was discovered that a coating composition for parts can be obtained, and the present invention was completed.

That is, the present invention provides the following three components 1M1 to (e);
al epoxy resin) 70% by weight of an aliphatic dihydrazide compound represented by general formula (I); (wherein n is a real number from 8 to 10)
The dihydrazide compound (C) containing the above inorganic extender pigment as an essential component, and the epoxy resin 1 of the above +a) component
00 parts by weight, the dihydrazide compound as the component (b) is 10 to 60 parts by weight, and the inorganic extender pigment as the component (C) is 60 to 60 parts by weight.
The present invention relates to a coating composition for electronic components, characterized in that the amount is 15,011 parts.

[Structure and operation of the invention]

The epoxy resin of component (a) used in the present invention includes bisphenol A epoxy resin, Talesol novolak epoxy resin, bisphenol F epoxy resin, alicyclic epoxy resin, phenol novolak epoxy resin, organic dibasic acid diglycidyl esters, epoxy resins having a hydantoin ring, and the like.

One or more of these epoxy resins can be used, but bisphenol A is particularly preferred.
It is preferable to use a type epoxy resin (epoxy equivalent: 300 or less) and/or a Talesol novolac type epoxy resin.

In the present invention, the dihydrazide compound used as a curing agent for the above-mentioned epoxy resin has the following general formula (I): Hz NHNH, .
An aliphatic dihydrazide compound represented by (7) (wherein n is a real number of 8 to 10), that is, a dihydrazide compound of risebacic acid and/or dodecanedicarboxylic acid, is used.

Here, in dihydrazide compounds of aliphatic dicarboxylic acids such as oxalic acid, succinic acid, malonic acid, and adipic acid, in which n in the general formula is 7 or less, the moisture resistance of the coating film becomes poor. Dihydrazide compounds of aliphatic dicarboxylic acids in which n in the general formula is 11 or more have poor heat resistance and are difficult to obtain as commercial products, making them impractical.

As mentioned above, the present invention is characterized by using a specific aliphatic dihydrazide compound in which n in the general formula is 8 to 10. 70% by weight or more, preferably 7% by weight of
If the amount is 5% by weight or more, the above object of the present invention can be achieved. In this case, the remaining 30% by weight or less of the dihydrazide compound may be the above-mentioned aliphatic dihydrazide compound in which n in the general formula is 7 or below or 11 or above, or the above-mentioned conventionally known aromatic dicarboxylic acid. Dihydrazide and the like may also be used.

The inorganic extender pigment (cl component) used in the present invention eliminates dripping when applying the paint composition to electronic parts, and also improves the durability (cold/thermal cycle resistance), moisture resistance, and other mechanical properties of the paint film. Known inorganic fillers that are essential for maintaining physical strength and are used in electronic component sealing materials, such as silica (particle size 5 to 50 μm), alumina, hydrated alumina, hydrated magnesium, and talc. , mica, calcium carbonate, barium sulfate, barium carbonate, zirconia, silicon nitride, boron nitride, aluminum nitride,
Clay etc. are used.

In the present invention, the mixing ratio of the above-mentioned elongation) to rc+ three components is 10 to 60 parts by weight, preferably 25 to 50 parts by weight of the BL component to 100 parts by weight of the 81 components,
tc+ component is 60-150 parts by weight, preferably 70-1
The amount is 20M parts.

If component (b) is less than 10 parts by weight, the effects of the present invention may not be obtained, and properties such as curability, moisture resistance, and solder resistance of the coating film may be impaired, and if it exceeds 60 parts by weight, However, no further improvement in performance can be expected, and it is disadvantageous in terms of cost. Furthermore, if the C1 component is less than 60 parts by weight, it will not be possible to prevent paint from dripping, improve the durability of the paint film (cold/thermal cycling properties), and moisture resistance, and if it exceeds 150 parts by weight, This results in a decrease in the moisture resistance and mechanical strength of the coating film.

The coating composition of the present invention uses the above three components fat to (C) as essential components, and if necessary, coloring pigments used in general coatings (such as titanium dioxide, carbon black, Bengara, Inorganic coloring pigments such as yellow iron oxide and various organic coloring pigments), various anti-moulding agents for rheology control (for example, fine powder silica with a particle size of 1.0 μm or less, organic bentonite, etc.), leveling agents, antifoaming agents,
A coupling agent or the like may also be used.

In addition, various non-reactive diluents (dioctyl phthalate,
plasticizers such as dibutyl phthalate-1), reactive diluents (
epoxy group-containing compounds having a lower molecular weight and lower viscosity than the epoxy resin of component ta), such as phenyl glycidyl ether and butylgrundyle ether), organic solvents, and known flame retardants for imparting flame retardance (bromine, etc.); epoxy resins, phosphate esters, antimony trioxide, etc.)
is also available.

Furthermore, in order to lower the curing temperature and shorten the curing time, imidazole, tertiary amines, carboxylic acids, chlorophenyl-1,1-N-dimethylurea, salts of organometallic compounds, etc. may be used as curing catalysts. Among these, imidazole and salts of organometallic compounds are particularly preferably used.

The coating composition for electronic parts of the present invention is generally treated as a liquid coating composition in which the above-mentioned components are uniformly mixed by an appropriate means. During storage for a long period of time, such as one month, problems such as rapid increase in viscosity or gelation do not occur.

The coating composition for electronic components of the present invention is prepared by uniformly mixing the above-mentioned components, applying it to the surface of an electronic component such as a fixed resistor by a conventional method, and drying it.
By heating and curing in a short time of 2 minutes, problems such as dripping do not occur during application (the thickness is usually 2 minutes).
A cured coating film with a diameter of 0 to 2.000 μm and a good appearance without pinholes or cracks can be formed.

In addition to the above-mentioned good appearance, this cured coating film has insulation resistance and
It has excellent moisture resistance, heat resistance, durability (cold/thermal cycling), etc., and also has good solder resistance, and there are no problems such as cracks occurring in the cured coating after immersion in a solder bath.
It exhibits very good performance as insulation and moisture-proof protection for electronic components such as fixed resistors.

〔Effect of the invention〕

As described above, according to the coating composition for electronic components of the present invention, which includes the three components (al to It can be cured quickly, and the cured coating film can satisfy all of the requirements such as solder resistance, insulation resistance, moisture resistance, heat resistance, and durability (cold/heat cycle resistance).

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples. However, the examples are not intended to limit the invention.

Examples 1 to 6 and Comparative Examples 1 to 6 Based on the formulations in Table 1, the epoxy resin, dihydrazide compound, inorganic extender pigment, and other components were mixed in advance, and the mixture was heated to 60°C using a three-roller. The mixture was dispersed and kneaded to a particle size of 4 μm to prepare 12 types of coating compositions for electronic components including Examples and Comparative Examples.

The following seven types of tests were conducted using each of the above-mentioned electronic component coating compositions as sample coatings. The results were as shown in Table 2 below.

(1) Storage stability: 70fl in a glass bottle with a depth of 80n and a cross-sectional diameter of 60mm.
A sample paint was poured into the container to a depth of 1,000 degrees Celsius, the container was sealed, and left to stand for 30 days in a constant temperature chamber at 40° C., and the initial and post-test viscosities were measured using a Rion Visco tester (20° C.; unit: poise). When the viscosity after the test was 1.5 times or less of the initial viscosity, it was considered to be passed.

(2) Painting workability and appearance A sample paint adjusted to 25°C was applied to a 1/4W type IMΩ carbon film fixed resistor and cured by heating at 170°C for 10 minutes. The test was passed if there was no sagging during application, the thickness of the cured film was at least 200 μm or more, and there were no pinholes or cracks in appearance.

(3) Moisture resistance test The resistor coated in (2) was energized at 250 VDC for 1.5 hours in an atmosphere of 85°C and 85% relative temperature.
A test was conducted for 250 cycles, with 0.5 hours of no current being applied as one cycle. Measure the resistance value at the initial stage and after the test,
The change rate of the resistance value after the test with respect to the initial resistance value is ±5%
If it was within the range, it was considered a pass.

(4) Heat Resistance Test The resistor coated in (2) was left standing in an oven adjusted to 155°C for 1,000 hours. After the test, if there were no cracks in the appearance and the rate of change in the resistance value after the test with respect to the initial resistance value was within ±1%, it was judged as passing.

(5) Durability (cold/thermal cycling) The resistor coated in test (2) was heated at 125°C for 30 minutes for 2
Five cycles of the test were conducted, with temperature changes of 5° C. x 10 minutes and -55° C. x 30 minutes as one cycle.

After the test, if there were no cracks in the appearance and the rate of change in the resistance value after the test with respect to the initial resistance value was within ±1%, it was judged as passing.

(6) Insulation resistance test Place the resistor painted in (2) inside the right-angled metal flock so that both ends do not protrude, and apply 500V DC voltage between the block and the lead wire. was applied for 2 minutes and the resistance value was measured. A value of 10,000MΩ or more was considered to be a pass.

(7) Solder resistance test The resistor coated in (2) was boiled in boiling water for 5 minutes and then immersed in a 280°C solder bath for 10 seconds. After the test, if there were no cracks in the appearance and the rate of change in the resistance value after the test with respect to the initial resistance value was within ±5%, it was judged as passing.

As is clear from the results in Table 2 above, the coating compositions of Examples 1 to 6 according to the present invention showed good results in all test items, and in particular had good moisture resistance and solder resistance. , fully meets the required characteristics for paints for electronic parts.

On the other hand, the coating compositions of Comparative Examples 1 to 6 failed in any of the items, and were particularly poor in moisture resistance and solder resistance, and did not meet the required characteristics for coatings for electronic components. In addition, since the coating composition of Comparative Example 4 was insufficiently cured, subsequent coating film performance tests were not conducted.

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Claims (1)

[Claims] (1) The following three components (a) to (c); (a) Epoxy resin (b) General formula (I); ▲There are numerical formulas, chemical formulas, tables, etc.▼...(I) (In the formula, n is 8 A dihydrazide compound containing 70% by weight or more of an aliphatic dihydrazide compound represented by: (c) Epoxy resin 1 containing an inorganic extender pigment as an essential component and the above component (a)
00 parts by weight, the dihydrazide compound as the component (b) is 10 to 60 parts by weight, and the inorganic extender pigment as the component (c) is 60 to 60 parts by weight.
A coating composition for electronic parts, characterized in that the content is 150 parts by weight.