Investigation of Acceleration factors for SnAgCu-Bi Solder Joints under various temperature cycling test conditions

Ball grid array (BGA) packages are widely used for computing and consumer electronics applications, and the Sn-Ag-Cu (SAC) lead-free solders have been used to meet the environmental regulations. Adding bismuth (Bi) to the SAC solder alloys has become popular approach to reinforce solder joint reliability for harsh environment such as automotive applications in recent years. The common acceleration models are normally used to predict the field life of the solder joints. However, the acceleration parameters in the acceleration models can be changed due to the solder materials, the acceleration factor (AF) modeling for SAC-Bi solder shall be studied. In this study, Board Level Temperature Cycling (BLTC) tests were conducted to investigate the effect of solder alloy and test Printed Circuit Board (PCB) configuration. The empirical AF of SAC+2% Bi solder was verified and compared with the AF of SAC solder, and the AF of the SAC+2% Bi solder was determined according to the PCB thickness. Also, an Accelerated Temperature Cycling (ATC) profile was suggested to reduce the test duration, and the AF of the ATC profile was compared with the AF of the automotive grade 1 (G1) profile.