Reliability of lead-free solders for die attach in automotive power modules

Four Sn- based solder joint materials SAC305, SnSb5, SnSb10 and PFDS400® were compared conducting active power cycling tests. In addition, the microstructure before and after the power cycling test was analyzed. Intermetallic compounds were detected at all tested solders after the soldering process. The composition and the amount of intermetallic compound (IMC) phases differed between the solders. The PFDS400® solder joint which consisted mostly of Cu
6
Sn
5
intermetallic compound and an intermediate copper layer showed the highest lifetime followed by SnSb5, SnSb10 and SAC305 solder. While SAC305, SnSb5 and SnSb10 failed due to material fatigue, the PFDS400® solder joint did not show any cracks, damage, or delamination.