Method of encapsulating electronic devices

Claim 1

A method for making plastic encapsulated electronic devices capable of exceeding a 50% survival rate when subjected to a moisture-ladened environment at a temperature of about 130° C. for a period of at least 100 hours under highly accelerated stressed test conditions, which comprises encapsulating the electronic devices at a temperature of 120° to 230° C. at a pressure of 400 to 1500 psi, with a heat curable composition comprising by weight, (A) 100 parts of an epoxy resin having less than 100 ppm of hydrolyzable chloride, (B) 10 to 100 parts of fused silica filler, (C) an amount of a compatible monomeric or polymeric onium salt catalyst as the diaryliodonium hexafluoroantimonate salt, which is sufficient to provide from about 0.01 to 100 mg. of antimony, per gram of epoxy and (D) up to 100 mg. of copper as a compound cocatalyst for (C), per gram of antimony.

Claim 2

A method for making plastic encapsulated electronic devices capable of exceeding a 50% survival rate when subjected to a moisture-ladened environment at a temperature of about 130° C. for a period of at least 100 hours under highly accelerated stressed test conditions, which comprises encapsulating the electronic devices at a temperature of 120° to 230° C. at a pressure of 400 to 1500 psi, with a heat curable composition comprising by weight, (A) 100 parts of an epoxy resin having less than 100 ppm of hydrolyzable chloride, (B) 10 to 100 parts of fused silica filler, (C) an amount of a compatible monomeric or polymeric onium salt catalyst as the diaryliodonium hexafluoroantimonate salt, which is sufficient to provide from about 0.01 to 100 mg. of antimony, per gram of epoxy and (D) up to 100 mg. of copper as a compound cocatalyst for (C), per gram of antimony.