Joint reliability of various Pb-free solders under harsh vibration conditions for automotive electronics

Abstract

These days, realization of technology for automotive electronics is important for convenience and safety in automobile industries. Although technology development is continuously progressing, various problems associated with the reliability of automotive electronics have arisen. In this study, combined vibration tests were performed to determine the reliability of various solders under harsh environments: Sn-3.0Ag-0.5Cu (SAC305), Sn0.7Cu and Sn-0.5Cu-0.01Al-0.005Si-0.008Ge (SnCuAl(Si)) solder (in wt%). The Pb-free solder balls were used on electroplating nickel finished Cu pads of a fine ball grid array (FBGA) package. The BGA packages mounted with solder balls were set up on electroless nickel-immersion gold (ENIG) finished Cu pads of a daisy-chained printed circuit board (PCB). The combined random vibration test was performed under 2.5 Grms in the range of 400 to 2000 Hz in the temperature range of −45 to 125 °C and was continued until 500 cycles. The reliability of the solder joint was determined by measuring the electrical resistance using a multi-meter. The resistance gradually increased and finally approached infinity. In addition, the IMC thicknesses increased during the combined random vibration test, which affected the fracture behavior. To determine the reliability of the solders, the number of failures of solders and the crack morphology and propagation in each solder were evaluated. Among the three solders, the SnCuAl(Si) solder demonstrated the best reliability.