The influence of silver content on the reliability of lead-free solder joints under drop condition

In order to explore the effect of the silver content of lead-free solder joints on the reliability in the drop condition, the drop tests were carried out with three different kinds of materials (Sn-3.0Ag-0.5Cu, Sn-1.0Ag-0.5Cu and Sn-0.3Ag-0.7Cu). The half sine input acceleration pulse was measured at the corner of the drop block, G levels and pulse duration are 1500 Gs and 0.5 millisecond. Using electrical test, optical microscope, scanning electron microscope and other means, the failure position of solder joint had be identified. Failed BGA solder joints were cross-sectioned and metallurgical analysis to investigate failure mechanisms of BGA lead-free solder joints under impact loading. The results showed that most of the failures locate in the PCB side for the three kinds of different joining materials, The most periphery solder joints are most likely to failure, and the thickness of IMCS gradually decrease and the life of solder joint gradually enhance with the content of Ag reducing.