加载速率和钎料厚度对SnAgCu/Cu焊点剪切行为影响

采用四种加载速率(1,0.1,0.01,0.001 mm/s),对四种钎料厚度(0.1,0.2,0.3,0.6 mm)的SnAgCu/Cu搭接焊点进行了剪切破坏试验,分析了不同加载速率以及钎料尺寸对焊点抗剪切性能的影响,并通过扫描电镜(SEM)和能谱仪(EDS)分析了剪切试样断口形貌、裂纹的萌生位置及扩展路径,阐释了SnAgCu/Cu焊点断裂失效机理. 结果表明,加载速率在0.001~1 mm/s范围内,焊点抗剪切强度随加载速率的增加而增大,不同加载速率条件下焊点的断裂模式都为韧性断裂. 不同钎料厚度的SnAgCu/Cu焊点随着焊点厚度的减小,其抗剪切性能提高,表现出明显的体积效应,其裂纹萌生位置逐渐由焊点内部向IMC层转移. 焊点断口形貌为拉伸撕裂型伸长韧窝和剪切平面,断裂机理为微孔聚集型-纯剪切复合断裂.

Effect of loading rates and solder thickness on shear behavior of SnAgCu/Cu lead-free solder joint

Single shear lap SnAgCu/Cu solder joints with different thicknesses (0.1, 0.2, 0.3, 0.6 mm) were tested at various loading rates (0.001, 0.01, 0.1, 1 mm/s) with an Instron5948 Micro Tester. The results show that the shear strength of solder joints increased with the increase of loading rates, and increased with the decrease of solder thickness, showing an apparent size effect. Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometer (EDS) were used to analyze the morphology of shear fracture and the crack initiation on the surface of solder joints, the crack initiation location gradually shifted to IMC layer from the solder with the decrease of solder thickness. The fracture morphology of solder joints had elongated dimples and shear planes, and the failure mechanism was micro-void aggregation/pure shear hybrid fracture.