热–机械应力和湿气引起QFN器件层间开裂分析

Analysis on Thermal-mechanical Stress and Moisture Driven Delamination in the QFN Package Devices

采用通用有限元软件分析和计算器件在潮湿环境下的潮湿扩散,并计算由于吸潮使器件在无铅回流的高温下产生蒸汽压力,并对层间开裂现象进行分析。结果表明,气压是层间开裂的主要原因,在气压和热机械应力的作用下,层合面上的微孔洞扩张并结合起来,导致器件最后失效。

The finite element analysis on moisture diffusion in microelectronic plastic packages during moisture precondition by using a commercial FEA software was studied and modeled. Then, the vapor stress which induced under lead-free reflow temperature was calculated. And delamination phenomenon appear in package was also analyzed. The results indicate that the vapor pressure is a major driven force for interface delamination. Under vapor and thermo-mechanical stress, the micro holes in the interface start to expand and combine. Finally, it induced delamination.