HIGH-PERFORMANCE SCREEN PRINTABLE SILICONE AS SELECTIVE HYBRID IC ENCAPSULANT

Silicone-based materials are some of the best encapsulants for protecting IC devices from exposure to alpha particle radiation, moisture, electrical, and temperature cycling for all AT&T's bipolar, MOS, and hybrid IC (HIC) devices. However, the two major drawbacks of the silicones are their poor solvent resistance and poor adhesion to gold-plated substrates. We have developed an excellent solvent, flux, and detergent resistant screen printable silicone (SPS) with a modest curing temperature and excellent adhesion to gold-plated substrates IC. In this paper, we describe the material formulation and need for an encapsulant with the above properties. Microdielectrometry was used to define the precise SPS cure schedule; temperature humidity bias was used to qualify the material's electrical performance; Auger spectroscopy and laser ionization mass spectrometry were used to further elucidate the crosslinking density and the interfacial interaction of the SPS and encapsulated substrate. © 1990 IEEE