IGBT模块焊层的被动热循环可靠性分析

Reliability analysis of solder layer of IGBT module under passive thermal cycling

有众多基于加速试验与数学模型研究焊层可靠性的方法被报道,但是这些方法对模块各焊层间的差异及失效机理认知不足.基于某款绝缘栅双极型晶体管(insulated gate bipolar transistor,IGBT)模块为研究对象,通过设计被动热循环(TC)加速试验,结合精细超声扫描(scanning acoustic microscope,SAM)的方法高效评价了不同焊层的TC耐热疲劳可靠性.结果表明,该封装体系下母排焊层的可靠性最差,衬板的可靠性最高.在热应力及化学势作用下,镀层中磷的相对含量及界面金属间化合物的厚度逐渐增加引起界面结构不匹配性增强,导致界面裂纹的萌生和生长,其中镀层结构的变化起主导作用.创新点:基于SnPbAg焊层与衬板及基板界面结构的动力学过程分析,明确了系统焊层退化及空洞产生的机理.

Many studies have been reported on the reliability of solder layers based on accelerated tests and mathematical models,but few of them provided insights into the differences and failure mechanisms among solder layers.This paper efficiently evaluated the thermal fatigue reliability of different solder layers of insulated gate bipolar transistor(IGBT)module by designed thermal cycling(TC)accelerated tests with the assistance of scanning acoustic microscope(SAM).The results showed that the reliability of the busbar solder layer was the lowest and that of the substrate was the highest under the IGBT packaging system.Under the action of thermal stress and chemical potential,the relative content of phosphorus in the layer increased,and the intermetallic compounds at the interface grew thicker,which has enhanced the incompatibility of the interface structure and resulted in the initiation and growth of cracks.During this process,the change in interface structure has played a key role.Highlights:Based on the dynamic process analysis of the interface structure between SnPbAg welding layer,substrate and base plate,the mechanism of the degradation of the system solder layer and the formation of voids is clarified.