Computational modeling and optimization for wire bonding process on Cu/low-K wafers

A methodology is developed to use the explicit dynamic analysis results to reflect the real impact responses of wire bonding under different CV (constant velocity) settings. The optimal ranges of the process parameter settings for wire bonding on Cu/low-K wafers are determined by this way. The KNS Maxum bonder is selected as the vehicle for mapping the process settings into the simulation. The approximate mathematical model of the capillary motion during the real bonding impact is established. The loading forces linearly ascending with time on the capillary is proposed into the explicit dynamic analysis, and the analytical equation under this loading condition is deduced. Two assumptions are put forward for linking the real bonding responses and the simulation results, and specifying the impact time for the explicit dynamic analysis. A series of impact simulations under various force loading profiles are performed for the current wire bonding case on Cu/low-K wafers. The impact time is fixed on and the simulation results perfectly match the deduced analytical expression unless the time is larger than the impact time. By investigating the regression relations both in the impact simulation and the real bonding process, the simulated bond ball shape responses are mapped to the CV settings. Through defining the reasonable range of deformation contribution from impact, the CV and bond force ranges as the optimal process settings are deduced out to achieve the target bond ball shape after ultrasonic. Finally, a comparison is made to evaluate the process settings obtained both from numerical analysis and DOE (design of experiment).