Reliability Assessment on the Re-Balling of PBGA from SnPb to Pb-Free Solder Spheres

Due to environmental consciousness and legislative regulations, lead-free solders will soon replace most of conventional lead-containing solders in microelectronic industry. However, it is an evident loss or waste to abandon these Pb-containing devices directly. This paper describes a new re-balling method to replace SnPb by lead free solder ball on BGA packages. After re-balling process, no Pb was detected in the solder balls by using EDX. Compared to as-reflow SnAgCu solder balls without the re-balling, no significant degradation of ball attachment strength was found on re-balled specimens. This paper discusses the effect of thermal aging at 150degC on the ball attachment strength with and without re-balling. The strength of solder balls is investigated by ball shear and cold bump pull (CBP) tests. The test configuration and the experimental data are reported in detail. The test results indicate that the ball attachment strength of re-balled balls after thermal aging is similar as the results without re-balling