A Study of Interfacial Moisture Diffusion at Metal/Epoxy Interface by FTIR Technique

The delamination at the copper lead frame and the epoxy interface adversely affects the reliability of IC packages and this is a common failure mode during the qualification process. One of the factors governing the interfacial delamination is the moisture content at the interface. This study developed the experimental measurement of interfacial moisture diffusion by Fourier transform infrared spectroscopy - multiple internal reflection (MIR-FTIR). In this study, MIR-FTIR measurement was conducted on isothermal gloptop epoxy system at different positions of sample with constant humidity level 85% relative humidity at 85 degree Celsius. By comparing the FTIR results on the epoxy samples with different pre-conditioning time, the interfacial moisture content at different position in epoxy sample was obtained and diffusion coefficient was calculated to compare with the bulk diffusion results. Mechanism of interfacial moisture diffusion was then characterized. This study has demonstrated the seepage mechanism along the copper/epoxy is the major driver for interfacial delamination under moisture pre-condition. It is likely that is the prevailing mechanism as compared to the established bulk diffusion mechanism in the epoxy molding compound.