Cu-Coated Zn/Al Clad Solder for High Temperature Die Attachment

Abstract

Zn/Al/Zn and Zn/Al/Cu clad materials were developed for high-temperature die attachment. The clad structure is used in an attempt to improve the wettability of Zn-Al solder by preventing oxidation of the Zn and Al. The materials were produced by clad-rolling Zn, Al and Cu strips, which act as solder following eutectic melting at temperatures above 382°C. The wettability, bondability and reliability of the clad materials were evaluated. The Zn/Al/Cu clad materials could be used in an atmospheric oxygen concentration of 100 ppm. The thermal cycle life of chip-to-substrate joints formed using the Zn/Al/Cu clad materials was four times longer than that formed using Pb-Sn-Ag solder.