在高速推力和高速拉力测试时，SnAgCu和SnPb焊料球的脆性破坏机制

Conclusions

This study investigated the brittle failure mechanism of high-speed ball shear/pull testing. Two kinds of solder alloys (SAC405 and SnPb) with ENIG package substrate pad finish were studied. The brittle fracture surfaces were inspected by SEM/EDX after ball shear/pull testing. The major findings follow:

1) High-speed solder ball shear and pull tests produced high brittle fracture failure rates, regardless of solder composition.

2) Solder ball pull testing generated a higher percentage of brittle failures than solder ball shear testing, at all test speeds, and for both SAC405 and eutectic SnPb samples.

3) In drop testing, SAC405 showed a greater susceptibility to brittle fracture than Sn-Pb solder alloy, coincident with the results of the high-speed solder ball shear and pull tests.

4) SEM imaging and EDX mapping of the fracture interfaces indicates that the brittle failures for the drop, shear and pull testing all occurred at the Ni/IMC interface and resulted in nearly identical fracture surfaces.

5) High-speed pull tests revealed the brittle interface with a greater sensitivity than in the ball shear test, especially for SnPb solders, due to the absence of secondary solder ball interactions with the solder mask and the already fractured surface.

6) SEM/EDX analysis of the fracture surfaces indicated that solder residue on the package pad is more prevalent for SnPb solder compared to SnAgCu solder, and for highspeed shear testing compared to pull testing.