Pre-Grafted, Rubber-Modified Epoxy Novalak Resin for Semiconductor-Grade Transfer Molding Compounds
Original Publication Date: 1988-May-01
Included in the Prior Art Database: 2005-Feb-15
This invention provides low stress epoxy-novalak resins by covalently incorporating a rubbery phase in the epoxy-novalak system. The new encapsulant material being disclosed can reduce the mechanical stress generated by the encapsulant on a silicon die. Therefore, ball bond sheer, aluminum line shifting and die cracking by stress can be reduced where plastic-leaded chip carrier packages are utilized. Rubber-modified bisphenol-A epoxy resins show improved impact strength and fracture toughness over unmodified resins. In these systems, a terminally reactive elastomer, e.g., carboxyl-terminated butadiene nitrile, is mechanically blended into the epoxy resins.