Sintered nanosilver paste for high-temperature power semiconductor device attachment

Abstract

Sintered nanosilver is a lead-free die-attach material that could substitute for solder alloys and conductive epoxies for packaging power semiconductor devices, especially for high-temperature applications. While the maximum use temperature of a solder is limited by its melting point, the sintered silver joint can be used above the processing temperature, thus enabling high-performance power devices based on SiC technology to operate at high temperature. It can be fired at temperatures below 300°C without requiring applied pressure to form a dense interconnection with thermal and electrical conductivities superior to those of common high-temperature solder alloys. Die-shear strengths between 25 and 35 MPa can be obtained which compares favourably to the shear strength of solder. Unlike solder, which tends to form large voids during reflow, the sintered silver has a low elastic modulus and a microstructure containing only randomly distributed micrometer-scale pores that eliminates hot spots in the joint.