Wire Bond Integrity Test Chip

Abstract

A special test chip and bonding diagram has been designed to nondestructively evaluate wire bond integrity of plastic encapsulated IC packages. Differential Kelvin resistance measurements as a function of bake time provide a quantitative measure of bond degradation. It was found that a 20 m¿ resistance increase corresponds to unacceptable performance in bond pull and ball shear. A hypothesis is advanced to explain the development of bimodal distributions of bond resistance change and bond pull strengths, which develop after long bake periods. This method was used for optimization of gold wire bonding to pure aluminum and silicon-doped aluminum, and for encapsulant selection.