Browse Prior Art Database

Modified Flexible Circuitry for TCE Matching

IP.com Disclosure Number: IPCOM000109142D
Original Publication Date: 1992-Jul-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 1 page(s) / 41K

Publishing Venue

IBM

Related People

Davis, CR: AUTHOR [+4]

Abstract

One of the major problems in large size VLSI packaging is the electrical and mechanical connections between different level packages. Usually, these different levels have different coefficients of thermal expansion (TCE). Thus, temperature variations cause strains in the interconnections. Such strains are carried primarily by the thin exposed metal leads at the ends of the flex. In those cases where large TCE or temperature differences exist, breakage and failure of the interconnections is common. One approach to solve the problem would be through the modification of standard flex circuitry. In this approach, flex layers with different TCEs would be laminated together such that at each end, the TCE of the last flex layer would match that of the package at that end. For example, flex for connecting Si (TCE=2.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 100% of the total text.

Modified Flexible Circuitry for TCE Matching

      One of the major problems in large size VLSI packaging is the
electrical and mechanical connections between different level
packages.  Usually, these different levels have different
coefficients of thermal expansion (TCE).  Thus, temperature
variations cause strains in the interconnections.  Such strains are
carried primarily by the thin exposed metal leads at the ends of the
flex.  In those cases where large TCE or temperature differences
exist, breakage and failure of the interconnections is common.  One
approach to solve the problem would be through the modification of
standard flex circuitry.  In this approach, flex layers with
different TCEs would be laminated together such that at each end, the
TCE of the last flex layer would match that of the package at that
end.  For example, flex for connecting Si (TCE=2.4 ppm) and FR4
(TCE=80 ppm) would start with an insulating substrate of a suitable
polymeric material which is TCE matched with Si.  This flex would be
processed by standard techniques to produce desired circuitry and
etched holes in flex.  To produce a match to FR4, polymers with a
larger TCE would be laminated at the appropriate location.  Such
lamination may be single or double sided and consist of one or more
layers.  In this manner, the strain would be distributed across
supported conductor lines, enhancing fatigue life.

      Disclosed anonymously.