Pan Pacific Symposium Conference Proceedings


Author: Stanton Dent
Company: Dow Corning Corporation
Date Published: 1/25/2000   Conference: Pan Pacific Symposium

Seika Machinery, Inc.

Abstract: Silicone encapsulants, conformal coatings, adhesives and potting compounds have long been used in electronic applications due to their low ionic content, high alpha purity, moisture insensitivity, high and low temperature performance, and excellent electrical properties. It is well known that the silicone material set has many advantages over organic compounds. It is equally well known that low molecular weight uncured silicones may outgas, or creep and can contaminate nearby surfaces. Silicone surface contamination may be detrimental to achieving good adhesion to the surface in further process steps.

Recent advances in electronic packaging have led to the development of chip scale packages (CSP’s), where the size of the package is the same as the size of the IC die or up to 20% larger than the die. The material requirements for this package have driven the demand for low outgassing silicone materials and have resulted in the development of a family of microelectronic grade silicone materials suitable for use in CSP’s.

The polymerization of silicone polymers and the root cause of silicone outgassing and creep will be discussed in detail. Use of non-microelectronic grade silicones in the initial development of CSP packages showed evidence of silicone contamination on the leads during lead bonding. This was confirmed using XPS. This data and the resulting development of special microelectronic grade silicone encapsulant and die attach materials are discussed. These microelectronic grade materials, produced using proprietary processes have eliminated the silicone contamination problem in the CSP manufacturing process. Currently there are several manufacturers of chip scale packages in full production who are successfully using these microelectronic grade silicone materials.

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