Diffusion and absorption of corrosive gases in electronic encapsulants

Plastic encapsulated microcircuits with aluminum triple track structures were exposed to mixed flowing gas conditions to simulate and accelerate possible environments during long-term storage. No increase in resistance was measured and no corrosion products were observed after 800 h of accelerated exposure. Further experimentation indicated that chloride gas reacts with surface moisture in microscale and macroscale voids within the encapsulant, creating chloride ions. These ions become strongly bound to ion getters present in the epoxy molding compound, trapping the chloride ions within the bulk encapsulant and effectively retarding the diffusion process, which could lead to corrosion at the surface of the die. 2002 Elsevier Science Ltd. All rights reserved.