Shock resistant and thermally reliable low Ag SAC solder doped with Mn

98.5Sn0.5Ag1Cu0.05Mn (SAC0510M) exhibits a melting behavior similar to SAC105. It is two times better than SAC105 in the dynamic bending test; more than 8 times better in the modified JEDEC drop test; and more than 40-60% better in the -55°C/125°C thermal cycling test. The reduced hardness and much thinner and stable IMC layer on Ni are responsible for the superior non-fragility, while the stabilized IMC and microstructure are responsible for the thermal cycling performance. A thinner IMC layer on Ni is more important than reduced hardness in improving non-fragility. The thermal cycling performance of SAC0510M may override SAC305. A high Tg brittle board causes poor drop test results due to pad cratering.