SMTA International Conference Proceedings


INVESTIGATION OF THE PERFORMANCE OF SAC AND SACBi LEAD-FREE SOLDER ALLOYS WITH OSP AND IMMERSION SILVER PCB FINISHES

Author: Manivannan Sampathkumar et al.
Company: Rochester Institute of Tech.
Date Published: 9/25/2005   Conference: SMTA International


Abstract: The primary objective of this research is to compare the performance of two lead-free solder alloys (Sn-Ag-Cu (SAC) and Sn-Ag-Cu-Bi (SACBi)) when assembled with OSP and Immersion silver (ImAg) PCB finishes. The performance of the solder joints obtained with these combinations of alloy and PCB finish is evaluated using shear testing, under as-soldered, thermal aging and thermal shock test conditions.

The shear energy required to shear the solder joints is used as the primary response variable to investigate the performance of the joints. Sn-Pb components assembled on a PCB with HASL finish using Sn-Pb solder is used as the control for comparing the performance of Sn-Pb and lead-free solder joints. Cross-sectional analysis is used to investigate the intermetallic growth due to thermal aging and crack propagation due to thermal shock.

Preliminary results reveal that under all three test conditions lead-free solder joints require higher shear energy than Sn-Pb solder joints. The two surface finishes used in this research were not found to be significantly affecting the solder joint strength. The SAC alloy was found to perform better under as-soldered and thermal aging conditions when compared to SACBi and Sn-Pb alloys. However, during thermal shock SACBi solder alloy exhibited superior performance.

Keywords: Lead-free, SAC, SACBi, thermal aging, thermal shock



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