An analysis case on the failure of BGA solder joints

Abstract

In this paper, a failure analysis on ball grid array (BGA) solder joints is revealed with the aid of scanning acoustic microscope (SAM), optical microscope (OM), scanning electron microscope (SEM) and strain tester. By employing both the nondestructive analysis and destructive analysis, it was found that crack of several BGA solder joints caused the failure of the printed circuit board assembly (PCBA). All the BGA solder joints were examined. The result demonstrated that all the cracked BGA solder joints located near the edge of the printed circuit board (PCB). The distribution of cracked BGA solder joints indicates that the crack might be related to the external mechanical stress, which was introduced from the V-cut board splitting process. To validate the assumption, strain test was performed to examine the stain introduced from all processes, including V-cut board splitting; manual soldering and other assemble processes. The result of strain test demonstrated that the maximum strain was introduced from the V-cut board splitting process. Moreover, the strain caused from another type of board splitting (stamp-hole board splitting) was tested as well. The strain was much smaller than that which was caused from the V-cut board splitting. After replacing the V-cut board splitting with stamp-hole board splitting, the failure of the PCBAs did not happen again, which was another strong proof of that the crack of BGA solder joints was related to large strain introduced from the V-cut board splitting.