Flip chip electromigration: impact of test conditions in product life predictions

In this study, fundamentals of flip chip electromigration is reviewed for thin film UBM (Al/NiV/Cu) with SnPb eutectic, SnPbCu, and SnAgCu solder joint structures. Impact of key test conditions (i.e., temperature and current density) on the product life prediction is illustrated through the construction of governing equation, using empirical data collected at different test regimes. Significance of secondary failure mechanisms is also demonstrated in terms of test conditions and substrate pad selection. Obviously, tests conducted at elevated temperatures (150°C and above) with high current densities would provide results in short time. Since it involves mix mode failures (UBM consumption and electromigration), it would also yield most conservative predictions for operating conditions. Tests conducted at comparatively lower temperatures (105°C - 125°C) validate this claim and provide accurate predictions for most field conditions.