Reliability of lead-free fine pitch BGA under thermal and mechanical impact

Abstract

In this paper, performance difference of fine pitch and normal pitch BGA under thermal and mechanical impact conditions has been evaluated by means of thermal shock test as well as board-level drop test. Influence of solder ball material and PCB pad finish was also investigated. The results reveal that decrease of solder ball pitch could lead to increase of vulnerability. Fine pitch BGA fails more rapidly subjected to thermal or mechanical stress. The combination of Sn1.0Ag0.5Cu solder ball and Cu-OSP PCB pad outperformed other testing groups in the research and is recommended for manufacturers. Failure analysis shows that dominant failure mechanism is brittle cracking within or near intermetallics formed between bulk solder and pad metal during soldering reflow process.