Fatigue Life Evaluation of Ball Grid Array Packages with Sn-Ag-Cu and Rare-Earth Addition Solder under Cyclic Bending Test

The reliability of BGA assembly packages were evaluated by rapid fatigue life test. Three-point bend fatigue life test method has been developed for Sn-Ag-Cu 305 and rare-earth addition Sn-Ag-Cu-Ce solder joints. In this study, BGA assembly with Ni/Au surface finish was tested under cyclic bending load at room temperature. The bending fatigue life of Sn-Ag-Cu 305 solder joint was compared with rare-earth addition Sn-Ag-Cu-Ce solder joint. Experimental results showed that the failure mode of cyclic bending test was similar to thermal cycling test, and the rare-earth addition solder joint has lower bending fatigue life than Sn-Ag-Cu 305. Failure mode analysis showed that the crack failure was due to solder joint fatigue and was only propagating through the joint, but not through intermetallic compound (IMC). This study also established a real-time monitoring reliability test method. It can easily find the location of failure solder joint and precisely predict solder joint bending fatigue life.