Intuitive and inexpensive method to evaluate flip chip bonding parameters of micro bump with wafer-level underfill material using glass substrate

Abstract

Flip chip bonding of chips coated with wafer-level underfill over optically transparent glass substrate allows ease of inspection of flip chip bonding quality immediately, without the use of equipment such as SEM, CSAM or the need for highly-trained staff to interpret results. This method is inexpensive to implement, while intuitive to the engineer identifying responses to parametric changes in the flip chip bonding process. Our work complements the existing tomography techniques used to evaluate flip chip quality and reduces the amount of laborious cross-sectioning needed, adding new perspectives to evaluating flip chip bonding quality. We identified indicators of good bonding responses to our process parameters in bonding wafer-level underfill chips over glass substrate. This allows relationships to be quickly established and phenomena to be assigned. This evaluative method was inexpensive to implement, and with results that are intuitive to interpret.