Drop Impact: Fundamentals and Impact Characterisation of Solder Joints

This paper presents a summary of the fundamental theories behind board level drop impact covering the dynamics of drop impact assembly, dynamics of PCB, as well as interconnection stress. This is followed by a comprehensive study of the fracture characteristics of solder interconnections under high-speed impact using a newly developed Micro Impactor which provides both the fracture strength as well as fracture energy of impact. The test matrix consists of 5 solder alloys, 4 pad finishing, 3 thermal histories, and 2 solder mask designs forming a total of 120 combinations. The test has highlighted weakness in NSMD design and caution on SnAgCu solder when used in drop impact application