CS253645B1 - A method of making a coating for protecting electronic components - Google Patents

Abstract

The solution is to create a coating for the protection of electronic components, e.g. electrical resistors, which is electrically and thermally insulating, resistant to mechanical damage, moisture, chemical influences and atmospheric influences. The coating consists of a basic sealant layer containing a binder component and inorganic fillers and pigments in a weight ratio of 1:1 to 2.5, and a sealing layer.

Description

FIELD OF THE INVENTION The present invention relates to a method of making a coating for the protection of electronic components, electrically and thermally insulating, resistant to mechanical damage, moisture, chemical and atmospheric influences.

Commonly used protective coatings are made of materials based on organic or inorganic binder bases. · The disadvantage of coatings containing organic binders is their limited heat resistance - they can usually be used at temperatures around 150 ° C - and often poor adhesion to metal components, especially at temperature · Not yet used for trains with an inorganic binder base do not fully meet the requirements resulting from the functions of electronic components · Their disadvantage is especially frequent chemical enteration with the base material, which for example, it changes the electrical characteristics of the resistors with an active metal oxide coating deposited on a ceramic substrate. • Inorganic coatings may need to be cured at temperatures above 300 ° C, limiting their applicability to lower shear components. demands on heat resistance or significantly changes electrical functional characteristics · Te applies to coatings containing masses of hydraulically setting binders, binder phosphate or silicate - toasted or fused and a substrate which, under thermal loading, lead to coating integrity problems. Neither diffusion or plasma coating complies with the requirements for protective coatings placed on electronic components, since they are extremely heavy on the coating and cause considerable fluctuations in the electrical properties.

These drawbacks are largely eliminated by the method of coating the electronic components of the present invention,

253 645, characterized in that on the surface of an electronic component, a manoso putty layer comprising 5 to 45% tactile · ethyl silicate hydrolyzed 60-90% of the etechiometric amount of water required for its complete hydrolysis, 5 to 45% by weight . a solution containing 35 to 45% by weight of silicone and / or methyl 11 horse resin having a molar ratio of siloxy and methoxy groups of 1 to 50 to 70% by weight of inert inorganic fillers and pigments with a grain size of more than 100 µm, e.g. The iron layer is cured by gradually increasing the temperature to a maximum of 350 ° C over a period of 10 to 60 min. the amount of water required for complete hydrolysis of the ethoxy groups and the resulting sealing layer is cured at 10 to 60 ° C for 1 to 10 hours and polymerized othyl silicate alternatively:

(A) methyl silicone resin solutions characterized by a 1: 1 molar ratio of methoxy groups to siloxy groups and a resin content of 28 to 33% by weight in the pitch, or

B) from a solution of silicone resin prepared by esterification of organo-silicon compounds with ethyl alcohol and subsequent hydrolysis of the resulting esters with a boiling point of more than 72 ° C, contained in the residue after rectification of methylchlorosilane and containing 35 to 45%

Polio resin types can be combined as binder components ·

The filler component of the sealant layer consists of mixtures in the given system of chemically inert oxides, silicas, aluminosilicates with grain size up to 100 µm.

The coating formed by the method according to the invention is an insulator with a sufficiently high cross-sectional stress, stable even under thermal, physical and chemical loads, corresponding to the limit states which may arise

253 645 in use · During the coating process, there is no physical or chemical interaction between the coating and the electrically active layer of the element, which would adversely affect its electrical functional characteristics. The coating is integral and adheres to all material constituents of the element, even under the thermal load corresponding to the conditions of use of the element. The coating is also resistant to mechanical damage during handling and elements, to moisture and to the environment. Its construction is feasible on a continuously operating device with the least energy demand. Finally, it also meets aesthetic demands.

The invention is illustrated in more detail by the accompanying examples; mm ceramic resistive bodies with a resistive layer of tin oxide m with a nominal value R * of 90 to 100 Ohms were applied.

Example 1

The composition of the mass for the formation of the base layer of the sealant was:

partially hydrolysed ethyl silicate 53 g silicone resin solution (A) 106 g colloidal SiO ₂ (eg siloxide) 1 g TiO ₂ - rutile 5 g ground quartz 230 g ground mica 20 g

This mixture was applied by pouring and curing by gradually raising the temperature up to am 160 ° C for 40 minutes at this temperature. After spontaneous cooling, the caulking agent - about 50% solution of partially hydrolyzed methyltriethexyailane in ethyl alcohol - was applied by pouring. It cured at 20 ° C for about 2 hours.

Example 2

The composition of the material for making the sealant layer was:

partially hydrolysed ethyl silicate 48 g resin solution (B) 112 g colloidal SiO ₂ (eg siloxide) 1 g

CrgO ^ 2 g ground quartz 280 g

The further procedure was similar to Example 1 except that

· .. '(·..' 1.> I.> · “0 *

253 645

Example 3

The weight reduction for the sealant layer was:

partly hydrolyzed oily silicate resin solution (A) resin solution (S) colloidal SiO ₂ (siloxide) ® * ®2θ3 ground quartz ground mica g 61 g 40 gg 5 g

250 g 10 g

The method of making the coating and sealing it was as in Example 1, wherein the final curing temperature of the sealant layer was 210 ° C and the sealing layer was cured for 1 hour · at 50 ° C,

The following tests were carried out with the resistors coated according to Examples 1 to 3:

- load test with rated direct current at ambient temperature of 70 ° C and duration of 1000 h · Change of resistance values so did not differ more than - 5

- long-term moisture test at a relative humidity of «95% and a temperature of 40 ° C for 56 days, under a DC voltage of 0.1 max · permissible. After 2 hours acclimatization under laboratory conditions, the samples were loaded with rated voltage for 24 h followed by pen readings. The resulting changes did not exceed - 5% of baseline,

- Mechanical strength test · Mechanical properties were shifted by standard test of adhesion under load of samples kg · Coatings of this test complied,

- Cooking test · Samples were immersed for 10 minutes in boiling, denin-pressed water · No visual effects were detected after removal,

- ultrasonic test · Washing of samples in an ultrasonic washer with water or ethanol did not cause any changes ·

The invention is particularly useful in the electrical industry.

Claims (1)

A method of making a coating for the protection of electronic components, characterized in that a cementitious layer comprising 5 to 45% by weight is applied to the surface of the electronic component. 60 to 90% of the sto-ionic amount of water required for its complete hydrolysis, 5 to 45% by weight of a solution containing 35 to 45% by weight of a silicone and / or methyl silicone resin with nolinamine submerged in 1: 1 siloxy and non-alkoxy groups and 50 to 70% of the weight. inert inorganic fillers and pigments having a grain size of less than 100 microns, for example iron oxide, chromium trioxide, silica, mica, the resulting layer ee cures by gradually increasing the temperature to a maximum of 350 ° C over a period of 10 to 60 min. for sealing, apply a solution containing 30 to 80% of nettriethoxysilane hydrolyzed with 50 to 90% of the sto-ionic amount of water required for complete hydrolysis of the ethoxy groups, and the resulting sealing layer is cured at 10 to 60 ° C for 1 to 10 hours.