Cratering response method to study the effect of ultrasonic energy on Cu-wire bonding quality

The paper presents a method for 50 μm Cu-wire bonding to study sub-percentage assembly yield loss due to cratering, so called “in-process” cratering. Test vehicle is an audio amplifier device assembled in a surface mount power package (HSOP). The method is based on high temperature aging followed by wire pull testing and has successfully been applied to determine the upper limit of the bond energy process window. After implementation in production, the shift to lower bond energy was controlled via regular ball shear production monitor and “in-process” cratering was no longer observed.