Effect of Ni Addition on Bending Properties of Sn-Ag-Cu Lead-Free Solder Joints

Effect of Ni addition on the bending properties of Sn-Ag-Cu lead-free solder joints was investigated. Three point bending tests were conducted with a 324pin flip chip specimen at 10 Hz frequency and with 3mm substrate displacement. The test temperatures were 298 K and 398 K. At each temperature, Sn-l.2Ag-0.5Cu with a small amount of Ni addition, LF35 showed higher performance. The reason LF35 showed higher bending performance was discussed based on a mechanical fatigue test using a micro bulk specimen. Ni addition caused a fine subgrain of j3 -Sn, hence the crack propagation mechanism is changed, resulting in the improved fatigue performance of LF35.