电-热-力耦合载荷下非均匀组织Cu/Sn-58Bi/Cu微焊点拉伸力学性能研究  

Tensile Performance of Inhomogeneous Microscale Cu/Sn-58Bi/Cu Solder Joints under Electro-thermo-mechanical Coupled Loads

作　　者：李望云 李兴民 汪健 梁泾洋 秦红波[1,2] LI Wangyun;LI Xingmin;WANG Jian;LIANG Jingyang;QIN Hongbo(School of Mechanical and Electrical Engineering,Guilin University of Electronic Technology,Guilin 541004;Guangxi Key Laboratory of Manufacturing System and Advanced Manufacturing Technology,Guilin University of Electronic Technology,Guilin 541004)

机构地区：[1]桂林电子科技大学机电工程学院,桂林541004 [2]桂林电子科技大学广西制造系统与先进制造技术重点实验室,桂林541004

出　　处：《机械工程学报》2022年第2期307-320,共14页Journal of Mechanical Engineering

基　　金：国家自然科学基金(51805103,52065015);广西自然科学基金(2018GXNSFBA281065,2018GXNSFAA281222);广西科技基地和人才专项(AD18281021,AD18281022);广西制造系统与先进制造技术重点实验室主任基金(19-050-44-003Z);2021年广西研究生教育创新计划(YCSW2021184)资助项目。

摘　　要：电子封装微焊点往往在电、热、力等多种载荷共同作用下服役,且具有鲜明的组织不均匀特征。研究电-热-力耦合载荷下电流密度和温度对电子封装组织不均匀线型Cu/Sn-58Bi/Cu微焊点拉伸力学性能及其尺寸效应的影响。结果表明,较低温度和较低电流密度情况下,随焊点高度降低,Cu基底对钎料的力学约束增强,焊点拉伸强度提高,断裂发生在钎料体内,呈韧性断裂,与室温无电流情况下的力学行为和断裂模式一致。钎料内Sn相与Bi相电流密度非均匀分布所致的局部电流拥挤现象使两相间的温度梯度明显增加,因此由热膨胀系数差异所致的相界面应变失配和界面应力增大,致使焊点强度低于室温无电流加载时的值。随着温度和电流密度升高,Sn相与Bi相界面及钎料与IMC层界面的应变失配和界面应力加剧,导致焊点拉伸强度进一步下降;同时,断裂位置从钎料基体内逐渐转移至钎料/IMC层界面处,断裂模式由韧性断裂转为韧-脆混合断裂。The microscale solder joint in electronic packaging usually serves under the coupled loading of electric current,heat and mechanical stress,which has a distinct inhomogeneous microstructure.Tensile performance of inhomogeneous microscale line-type Cu/Sn-58Bi/Cu solder joints with different current densities and temperatures as well as their size effects are investigated under electro-thermo-mechanical coupled loads.The results show that at low current densities and temperatures,as the height of solder joints decreases,the mechanical constraint of Cu substrate on solder increases,which enhances tensile performance of solder joints;the fracture occurs in solder matrix,showing a ductile fracture mode.These are consistent with the mechanical performance and fracture behaviour of solder joints under tensile load without electric current stressing at room temperature.The local current crowding caused by the non-uniform distribution of current densities in Sn and Bi phases increases the temperature gradient between them.The mismatch strain and stress at the Sn/Bi interface increase due to the difference in coefficient of thermal expansion between Sn and Bi.Therefore,the tensile strength of solder joints under electro-thermo-mechanical coupled loads is lower than that at room temperature without electric current stressing.As the current density and temperature increase,the mismatch strain and stress at the Sn/Bi interface and the solder/IMC layer interface increase,resulting in further decrease in tensile strength of solder joints.Moreover,the fracture location gradually changes from the solder matrix to the solder/IMC layer interface,while the fracture mode shifts from ductile fracture to ductile-brittle mixed fracture.

关 键 词：组织不均匀微焊点 电-热-力耦合载荷 拉伸力学性能 

分 类 号：TG115[金属学及工艺—物理冶金]