The examination of the drop impact test method

The purpose of this study is to establish an experimental method of drop impact reliability for solder joints and an assessment method. The drop impact problem is composed by various factors. Such as, a drop impact induced flexural vibration of PCB (Printed Circuit Board), collision attitude, and dynamic fracture of solder joints. There are many methods examine impact reliability of BGA solder joints. One of the methods is a repetitive drop test with a simple equipment proposed by the authors. In a previous report, it was shown that the dynamic deformation of the PCB shows very stable results by attaching a hemisphere on the jig bottom. And as a result, the relation between drop height and cycle to failure of CSP package was obtained. It can achieve very good certainty of the fatigue test. However, several stable fatigue modes occurred according to the drop height. In this study, to obtain the impact reliability of BGA solder joints, the jig has been improved. In this paper, the authors carried out transient response analysis, and examined how the stresses of each device parts are affected by the jig´s dimensions. And then, they conducted the repetitive drop test to study how the analytical results will agree with the experimental results. Finally, based upon the analytical and experimental results, they proposed a drop impact reliability assessment approach.