Formulation and Characterization of Electrically Conductive Adhesives for Electronic Packaging

Abstract

A series of high-temperature stable electrically conductive adhesives (ECAs) was developed. Their matrix resin contained a functional epoxy, a reactive diluent, a silane coupling agent, and a curing agent. These ECAs included uni-modal ECAs with micro silver flakes only, bi-modal ECAs with micro silver flakes and micro silver spheres, tri-modal ECAs with micro silver flakes, micro silver spheres, and nano silver spheres. They all were made up of 15 wt% of matrix resin and 85 wt% of total silver fillers. All had reasonable viscosity, low bulk resistivity, and high thermal conductivity. Their bulk resistivity in the in-plane direction was as low as 5 × 10−5 Ω · cm, and different silver fillers had different effects on this. Their thermal conductivity in the vertical direction, from 5 to 7 W · (mK)−1, was usually lower than that in the in-plane direction from 15 to 30 W · (mK)−1. These ECAs could be cured at 130°C or any higher temperature than this with different curing time, and they all had high temperature stability. Their pyrolysis temperature was above 350°C.