焊点热疲劳失效原因分析

Cause Analysis of Thermal Fatigue Failure of Welding Spot

某PCBA样品在使用约半年后出现功能失效,该PCBA在封装后进行整体灌胶,将失效样品剥离,发现部分器件直接脱落,通过表面观察、切片分析、EBSD分析、应力分析、热膨胀系数测试等手段对样品进行分析,结果表明:各封装材料存在热失配,且焊点缺陷较多且存在应力集中区,加速焊点的疲劳失效进程,导致PCBA功能失效。

A PCBA sample has a functional failure after using about six months. After package, the PCBA is overall glued. Some devices directly fall off after peeling failed samples. Samples are analyzed by means of surface morphologic observation, micro cross section inspection, EBSD analysis, stress analysis, thermal expansion coefficient test and so on. The results show that the presence of thermal mismatch of materials, and a large amount of solder joint defects and the stress concentration accelerate solder joint fatigue failure process, which cause functional failure of PCBA.