Electrical performance and reaction kinetics of silicone gels
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Silicone gels are becoming more accepted as protective coatings for Very Large Scale Integrated circuits (VLSI) against severe environments due to their excellent electrical, thermal, and mechanical properties. Recent studies indicate that high performance silicone gels in low-cost, non-hermetic plastic packaging may replace conventional hermetic ceramic packaging. This paper describes the use of the soft silicone gels as coatings on Integrated Circuit (IC) devices, and the correlation between the material's cure temperature and cure time versus their adhesion and electrical reliability during 85 CC, 85% RH and bias accelerating testing. In addition, the reaction kinetics of the silicone gel based on the Differential Scanning Calorimetry (DSC) study of the uncured sample will be reported.
I. INTRODUCTION
Recent advances in integrated circuit (IC) technology have had a profound technological and economic impact on the electronics industry. The exponential growth of the number of components per chip, the exponential decrease of feature dimensions,1 and the steady increase in IC chip size have imposed stringent requirements not only on IC physical design and fabrication, but also on the IC encapsulants. The effectiveness of these high performance encapsulants, such as silicones (elastomers and gels), polyimides, epoxies, silicone-polyimides, and polyxylylene (Parylene) in protecting these large IC devices has been reviewed.2 4 High performance silicone gels possess excellent electrical, chemical, and physical properties for this type of IC protection. With their high purity, intrinsic low modulus, and soft gel-like nature, silicone gels have become very effective encapsulants for the delicate larger chip size and wire-bonded VLSI chips. Recent studies indicate that adequate IC chip surface encapsulation with these high performance silicone gels in plastic packaging might even replace conventional ceramic hermetic packages.5'6 This paper reviews some potential encapsulants, with special focus on the high performance silicone gels, their cure chemistry, and Temperature Humidity Bias (THB) accelerated electrical testing as a VLSI device encapsulant. The purpose of encapsulation is to protect electronic IC devices and prolong their reliability. Moisture, mobile ions (e.g., sodium, potassium, chloride, bromides, fluorides), UV-VIS and alpha particle radiation, and hostile environmental conditions are some of the possible sources of interaction which negatively affect the device performance and lifetime. Commonly used passivation layers, such as silicon dioxide, silicon nitride, and silicon-oxy-nitride, have excellent moisture and mobile ion barrier properties J. Mater. Res., Vol. 5, No. 4, Apr 1990
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and are used on the first layer in the encapsulation of a sodium ion barrier. In general, silicon dioxide is inferior to silicon nitride as a mobile ion barrier; however, the use of phosphorus-doped (a few weight percent) silicon dioxide has greatly improved its mobile i
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