Experimental parameter identification and validation of a process model for ultrasonic heavy wire bonding

Abstract

Ultrasonic heavy wire bonding is a standard process in packaging technologies of power semiconductor modules. Due to increasing demands on reliability of the electrical contacts under high temperature loads, copper wires with significantly better electrical and thermal properties compared to aluminum are used more often nowadays. This results in new challenges in process development due to higher process forces and ultrasonic power; for this purpose, a simulation model has been developed to improve process development. The process model is based on a co-simulation with sub-models for the different physical phenomena. The sub-models are based on parameters, which need to be identified from measurements. This contribution focusses on the identification of the material model. Therefore, a method is presented, which allows for an iterative identification of the stress-strain characteristics from compression tests based on a modified tensile-compression machine. In compression tests under ultrasonic load, the bond wire material behavior under ultrasonic load is investigated to characterize the so-called ultrasonic-softening-effect. The simulation model with identified model parameters is then used to predict main-effects-diagrams for aluminum and copper wire bond processes on DCB. The simulation results are validated by comparison to results from parameter studies of ultrasonic heavy wire bonding experiments.