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Enhanced Chip Encapsulant

IP.com Disclosure Number: IPCOM000037989D
Original Publication Date: 1989-Sep-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Ameen, JG: AUTHOR [+4]

Abstract

At present, there are two encapsulants for use on chips (the so called "glob-top" application). One is a silicone for reduced stress, the other is an epoxy for solvent resistance. This disclosure describes one encapsulant that has both properties.

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Enhanced Chip Encapsulant

At present, there are two encapsulants for use on chips (the so called "glob- top" application). One is a silicone for reduced stress, the other is an epoxy for solvent resistance. This disclosure describes one encapsulant that has both properties.

Thin film device carriers rely on an encapsulant to be placed over the chip to protect the IC from the environment. At present, silicones are used because they are elastic and hence greatly reduce the stresses impressed upon the chip. They also have the ability to dissipate stresses that are generated from mismatches in the coefficients of expansion during thermal cycling through this elasticity. This class of material has one serious drawback. They swell significantly in Freon TMS* - a common PC assembly solvent used for cleaning. To get around this problem, epoxies are a good alternative. However, these materials tend to generate too much stress during thermal cycling and cause them to be excluded from use on larger chips. To produce a material having the solvent resistance and elasticity of an epoxy, the following is proposed: 1) Mix 25-50% of a flexible, yet non-solvent-resistant epoxy, such as Scotchcast XR3259** to a non-flexible solvent- resistant epoxy, such as Hysol 4322***.

The resultant mix produces a flexible, solvent-resistant encapsulant that can be used on all size chips. * Trademark of Dupont, Wilminton, DE ** Trademark of 3M, St. Paul, MN *** Trademark of Dexter-Hysol, Olean,...