The Mechanisms that Provide Corrosion Protection for Silicone Gel Encapsulated Chips

Plastic molded packages have difficulty achieving high reliability with pin counts over 100 pins. Plastic pin-grid-array packages with pin-embedded printed circuit boards have been previously reported with silicone gel encapsulation that have both high reliability and low cost, and their development has been previously reported. The full detail of the relationship between reliability and process variations has only recently become better understood. Under some situations, voids can form in the gel coatings during the severe changes of temperature and pressure in autoclave "pressure cooker" accelerated testing. The procedures for avoidance of these voids and the effects of outside contamination of the package are discussed.