Method for reducing coefficient of thermal expansion in chip attach packages

Abstract

A simple, inexpensive, drillable, reduced CTE laminate and circuitized structure comprising the reduced CTE laminate, is provided. The reduced CTE laminate comprises: from about 40% to 75%, preferably from about 55% to 65%, by weight resin; from about 0.05% to 0.3%, preferably from about 0.08% to 0.10%, by weight curing agent; from about 25% to 60%, preferably from about 30% to 40%, by weight, woven cloth; from about 1% to 15%, preferably from about 5% to 10%, by volume, non-woven quartz mat. The present invention also generally relates to a method for reducing the CTE of circuitized structures, and to methods for making reduced CTE laminate and circuitized structures comprising reduced CTE laminate. The method for making reduced CTE laminate and laminate structures comprises the following steps: providing non-woven quartz mat; providing a prepreg, preferably B-stage cured to not more than about 40%, preferably not more than 30% of full cure; sandwiching the non-woven quartz mat between two layers of prepreg, and reflowing the resin of the prepreg into the quartz mat. The method further comprises providing a resin volume percent, woven glass cloth volume percent and metal volume percent of the circuitized structure to be fabricated; selecting a desired CTE for the circuitized structure to be fabricated; and determining the amount of non-woven quartz or non-woven glass mat to be incorporated according to a formula. Optionally, the reduced CTE laminate is sandwiched between two layers of metal, preferably copper.