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CONTROLLED EXPANSION ORGANIC SUBSTRATE CHIP CARRIER

IP.com Disclosure Number: IPCOM000005949D
Original Publication Date: 1990-Oct-01
Included in the Prior Art Database: 2001-Nov-19
Document File: 1 page(s) / 73K

Publishing Venue

Motorola

Related People

Frank Juskey: AUTHOR [+3]

Abstract

Current technology for fabrication of leadless chip carriers employs substrate materials that are made from w-fired alumina and tungsten. Additionally the covers used to mechanically protect the wire bonds and die attached to the substrate are also made from alumina. This package while very rugged and versatile is extremely expensive and requires up to 26 weeks to tool up for production quantities. Organic substrates such as conventional printed circuit board composite structures while being less expensive and requiring much less tooling time do not exhibit the required low coefficient of expansion (TCE) that is available from inorganic materials such as alumina. Also, use of conventional organic com- posite substrates just transfer the mechanical stress from the solder joints to the silicon chip.

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MO7VROLA Technical Developments Volume 11 October 1990

CONTROLLED EXPANSION ORGANIC SUBSTRATE CHIP CARRIER

by Frank Juskey, Barry Miles and Bruce Freyman

   Current technology for fabrication of leadless chip carriers employs substrate materials that are made from w-fired alumina and tungsten. Additionally the covers used to mechanically protect the wire bonds and die attached to the substrate are also made from alumina. This package while very rugged and versatile is extremely expensive and requires up to 26 weeks to tool up for production quantities. Organic substrates such as conventional printed circuit board composite structures while being less expensive and requiring much less tooling time do not exhibit the required low coefficient of expansion (TCE) that is available from inorganic materials such as alumina. Also, use of conventional organic com- posite substrates just transfer the mechanical stress from the solder joints to the silicon chip.

   A new reinforcement material called aramid paper is becoming available which will deliver a low cost quickly tooled alternative to conventional composites with the added advantage of having an expansion coefficient that can be tailored to the specific job. The new aramid paper just becoming commercially available has a CTE that is negative and when coupled with an epoxy resin it can produce a composite structure with a CTE as low as 7 ppm. By varying the aramid to resin ratio the TCE can be modified between the ranges of of 7-15 parts per million. The aramid would be used as the reinforcement media in place of the industry standard "E" glass. For years aramid in a woven form has been available for the reinforcement of printed circuit boards. The major problem with woven aramid, or more commonly called Kevlar (DuPont Trademark), is the inability t...