Investigation of the Lead-free Solder Joint Shear Performance

Reflow profile has significant impact on solder joint performance because it influences wetting and microstructure of the solder joint. The purpose of this study is to investigate the effects of reflow profile and thermal shock on the shear performance of eutectic SnPb (SnPb) and Sn3.0Ag0.5Cu (SAC305) solder joints. Test boards were assembled with four different sized surface mount chip resistors (1206, 0805, 0603 and 0402). Nine reflow profiles for SAC 305 and nine reflow profiles for SnPb were developed with three levels of peak temperature (12°C, 22°C, and 32°C above solder liquidus temperature, or 230°C, 240°C, and 250°C for SAC 305; and 195°C, 205°C, and 215°C for SnPb) and three levels of time above solder liquidus temperature (30 sec., 60 sec., and 90 sec.). Half of the test vehicles were then subjected to air-to-air thermal shock conditioning from −40 to 125°C. The shear force data were analyzed using the Analysis of Variance (ANOVA). The fracture surfaces were studied using a Scanning Electron Mi...