Effect of Ag content on microstructure and fatigue crack of SAC lead free solder balls under rapid thermal fatigue
Effect of different Ag content on microstructure, internal and external fatigue cracks of SAC lead free solder balls (Sn0.7Cu, SAC0307, SAC105) under the rapid thermal fatigue was studied. The result shown that the surface cracks of balls with three kinds of silver content were found after similar rapid thermal fatigue cycles. With the increase of thermal fatigue cycles, surface cracks became wider and deeper under the thermal stress. The number of crack was largest on the surface of SAC105 solder ball and cracks grew up fastest. The recrystallization and grain directional growth preferentially occurred at the bottom of solder ball under the heat flow, and the inhomogeneity of microstructure and coarsening of grains were most significant inside the SAC105 solder ball. Internal cracks were appeared near the heat source of solder ball preferentially, cracks mainly originated from brittle phase and cavity, and the fracture pattern was intergranular fracture and transgranular fracture. The number of internal crack was largest inside SAC105 solder ball, The internal cracks were honeycomb shaped and grew toward the heat source. Therefore, the research had a guiding significance for the performance evaluation of lead free solder for high power devices.
2020 21st International Conference on Electronic Packaging Technology (ICEPT)