Evaluation on bonding reliability of SAC305/Sn-57.5Bi-0.4Ag BGA solder joints with drop impact test

Due to the recent use of thin PCB or flexible PCB, the warpage problem of substrate is a critical issue. As one of the methods to reduce warpage, a method of lowering the reflow process temperature using a low-temperature solder paste is being studied. In this study, the reliability of SAC305/Sn-57.6Bi-0.4Ag solder joint was evaluated. After forming the BGA solder joint with the solder bump of Sn-3.0Ag-0.5Cu and the solder paste of Sn-57.6Bi-0.4Ag, the cross-sectional micrographs of the solder joint according to thermal aging (Temperature: Bottom 85℃ / Top 85℃ / Room 85℃, Time: 100, 500, 1000 h) was analyzed, and a drop impact test was performed. Failure number of drop impact increased with increasing aging time due to the coarsening of Bi and Sn phases.