Abstract
In electronic package technology, solder joint is not only used for the electrical connection and mechanical connection, but also offering the channel of heat dissipation. As chip package had developed from pin through-hole to pin surface mount, until the current no-pin ball array surface mount. Electronic package is developing in the direction of smaller ball grid array pitch, smaller chip size and more number of solder balls. The fact makes the reliability problem of solder joint become more and more outstanding. Studies have shown that 70 percent of electronic devices’ failure was caused by the failure of package assembly, and the failure of solder joint is the main reason in electronic package. The main failure mechanism of solder joint is low cycle thermal fatigue, and failure reason is the coefficient of thermal expansion (CTE)’s mismatch between components and circuit boards, then the thermal stress and strain don’t match in solder joint. The uncoordinated thermal strain will produce stress concentration, leading to the crack initiation and propagation, finally the solder joints’ failure.
