The Effect of the SnAg Solder Joint Morphology on the Thermal Cycle Reliability of 40 µm Fine-Pitch Cu-Pillar/SnAg Micro Bump Interconnection

In order to investigate the effect of the SnAg solder joint morphology on the thermal cycle reliability of Cu-pillar/SnAg micro bump interconnection, conventional single layer non-conductive films (NCFs) and double layer NCFs(D-NCFs) were compared. D-NCFs consisted of two NCF layers can successfully prevent SnAg wetting on the Cu bump sidewall. Due to the coefficient of thermal expansion (CTE) mismatch of several materials at the solder joint, the assembled solder joints can be significantly affected by the solder joint morphologies during the thermal cycle test. In this study, two kinds of solder joints were prepared using two conventional single layer NCFs and one D-NCFs with different thermo-mechanical properties such as CTE and modulus. As a result, assembled interconnections using D-NCFs showed much better thermal cycle reliability than that of conventional single NCFs, because the remaining Sn at the solder joint reduced the CTE mismatch damages and significantly enhanced the solder joint reliability.