热循环过程中焊点残余应变的研究

采用激光云纹干涉法,测量了不同热循环规范下焊点内的残余应变分布及最后失效的的焊点内最大的累积残余应变(即累积塑性变形),结果表明:材料热膨胀系数的不匹配导致焊点中存在很大的剪切变形,而且焊点内的残余应变的分布是很不均匀的;对应于同一种焊料,不同的热循环规范下焊点失效时的累积塑性变形基本上相同,可以认为对于焊点来说,失效时的累积塑性变形是一个常数,这可以作为热循环过程中焊点失效的判据。

Accumulated Residual Plastic Strain of Solder Joints under Thermal Cycling

The high sensitivity moir?interometry method was used to measure the residual thermal strain distribution and the maximum accumulated residual strain (accumulated plastic strain) of solder joints in different thermal cycling parameters. The experimental results show that the mismatch of CTE between the two parts jointed by the solder joints results in large shear strains in the solder joints, and the strain distribution is not uniformity; to one solder, the accumulated plastic strain to the failure in different thermal cycling rules is almost the same, to the solder the accumulated plastic strain to the failure is a constant.