CZ279560B6 - Compound for electronic components encapsulating - Google Patents

Abstract

The casting compound for electronic components is manufactured as a reaction product of anhydrous castor oil and a polyisocyanate resin in weight ratios of from 100: 5 to 100: 35, curable in a temperature range of 0 to 110 ° C and 20 minutes to 6 hours, obtainable from almost liquid to solid consistency

Description

Casting compound for electronic components

Technical field

The present invention relates to an embedding compound for electronic components which allows a tight and flexible embedding of a component with perfect insulation from adverse environmental influences, with good heat dissipation and practical self-extinguishing properties.

BACKGROUND OF THE INVENTION

Epoxy resins, asphalts, polyurethane resins and the like are used as encapsulating materials for electronic components. These substances are used with various fillers, accelerators and desiccants that affect their electrical and chemical properties as well as flame retardancy. The difficulty is the complexity of preparation, high cost and harmonization of all required properties. In most cases, these compositions are characterized by contradictory properties - for example good insulating properties, but considerable internal stresses during the curing process, for example of epoxides, often associated with an exothermic reaction. Another example is SU 430 124, which uses toluene as a solvent for a mixture of castor oil and an aliphatic and aromatic diisocyanate, but this greatly increases the curing time and, moreover, toluene is very harmful. According to EP 364 738, a catalyst such as a quaternary amine and a tin compound is required in the reaction of castor oil and diisocyanate, which is detrimental to the electroinsulating and dielectric properties of the encapsulant and thus practically unusable for electronic components. In addition, castor oil is used with the addition of condensation products of cyclohexanone and formaldehyde, possibly neopentyl glycol and adipic acid, which is also hazardous for electronic components. Last but not least, there are also problems related to ecology and safety at work with the present encapsulating materials.

SUMMARY OF THE INVENTION

The disadvantages of the embedding compositions used hitherto are solved by the embedding composition according to the invention. The principle of the embedding compound for electronic components is that it is a reaction product of anhydrous castor oil and a polyisocyanate resin, the main component of which is triphenylmethane-4,4 ', 4' '- triisocyanate, in a ratio of 100 parts by weight of castor oil to 5 parts. up to 25 parts by weight of a polyisocyanate resin. The encapsulant is cured at temperatures ranging from 0 to 75 ° C for 20 minutes to 6 hours as required.

The advantage of the encapsulant over the known compositions is that it does not contain harmful organic solvents such as toluene, shortens the curing time at lower temperatures without requiring further hardening, and exhibits very good final properties such as dielectric and electroinsulating properties, thermal conductivity and resistance, mechanical flexibility, vapor and gas tightness, and very good adhesion to commonly used materials.

The casting compound according to the invention can be achieved by varying the mixing ratio of the castor oil with the polyisocyanate resin, the main component of which is triisocyanate, optimizing the resulting properties for a given application, without the use of fillers, drying agents, accelerators and after stiff.

DETAILED DESCRIPTION OF THE INVENTION

A roll of capacitor, wound from polypropylene foil, metallized with aluminum, is mixed in a jail case with a mass prepared by mixing vacuum-dried castor oil with a low polymerized polyisocyanate resin, the main component of which is triphenylmethane 4,4 ', 4' 'triisocyanate, in 100 parts by weight castor oil, to 25 parts by weight of a polyisocyanate resin. The mass is allowed to solidify at 75 ° C for 2 hours. Further, the production of the capacitor is completed in a conventional manner.

For comparison, a capacitor without the use of encapsulating material (the so-called dry version) and a capacitor with a coil embedded in epoxy resin are used.

After carrying out the capacitor lifetime test (400 hours, 85 ° C, 340 V, 6 μιη polypropylene foil, aluminum metallized), the following average capacitance drops occur with the capacitors tested:

(a) capacitor without encapsulating material: C (%) = 2.25

(b) Epoxy resin encapsulated capacitor: C (%) = 0.65

c) a mass encapsulated capacitor according to the invention: C (%) = 0.35

The test result shows a considerably smaller capacity drop in the capacitor encapsulated by the encapsulating compound of the invention. Said encapsulating material slows the electrochemical oxidation process of aluminum or other capacitor coating under AC voltage due to perfect sealing of the coil and preventing external moisture and air oxygen from entering.

Industrial applicability

The encapsulant according to the invention makes it possible to improve the parameters of the encapsulated parts, to increase their resistance to air oxidation, wetting, thermal stress and resistance to shocks and combustion. It allows to extend the range of use of components and significantly extend their service life.

PATENT CLAIMS

Claims (1)

Encapsulant for electronic components, consisting of a polyisocyanate resin, the reaction product of anhydrous castor oil and triphenylmethane-4,4 ', 4' '- triisocyanate in a weight ratio of 100: 5 to 100: 25, cured for 20 minutes to 6 hours at a temperature · 0 to 75 ° C.