Toughened polycyanurate thermosets for electronic applications

Abstract

Polycyanurate thermosets are an emerging class of materials with applications in both the electronic and aerospace industries. For electronic applications these materials are currently being evaluated as high temperature adhesives, encapsulants, thin film dielectrics, and as matrix resins for multichip module laminates and printed-wiring circuit boards. Cyanate based thermosets possess an excellent combination of properties such as strong adhesion to metals, chemical resistance, thermal stability and outstanding electrical properties. However, the actual use of these materials has been limited due to their brittle nature and susceptibility to cracking. Efforts have been made to rubber toughen these materials but the enhanced toughness is achieved at the cost of high temperature performance. In this investigation, thermoplastic modification was evaluated as a method to increase the fracture toughness of cyanate ester based thermosets without sacrificing thermal stability. The approach utilized was to design a highly compatible engineering thermoplastic which upon curing would form a microphase-separated, multiphase network. Multiphase thermosets of this type typically possess enhanced fracture toughness; indeed, the thermoplastic toughened polycyanurates evaluated in this study showed a 5 to 10 fold enhancement in fracture toughness.