Fatigue Performance of Ball Grid Array Components at Elevated Temperature

The reliability of an electronic product highly attributes to the fatigue failure of an interconnected solder joint. The normal operating temperature for many electronic assemblies is at elevated temperature, such as automotive under-the-hood applications. Therefore, it is essential to study the fatigue performance of the electronic components at elevated temperature. This study includes customized sandwich Ball Grid Array test vehicles with 3×3 solder joints connected between two substrates. The tested solder alloys were SAC305 (Sn-3Ag-0.5Cu), SnPb (63Sn37Pb), and SAC-Bi (Sn-3.41Ag-0.52Cu-3.3Bi). Instron Micromechanical Tester is used to perform strain-controlled fatigue tests at elevated temperature of 75 °C. The surface finishes of the electronic assemblies were OSP and ENIG. The hysteresis loops for each sample were systematically recorded to measure inelastic work per cycle and plastic strain range. It is found that the elevated temperature would have a negative effect on the fatigue life of all the tested materials. OSP surface finish performs better than the ENIG surface finish at elevated temperature. It is also found that increasing the temperature has less effect on the fatigue life of SAC-Bi, compared with SAC305 and SnPb.