(1. 重庆大学 机械传动国家重点实验室，重庆 400030； 2. 重庆科技学院 冶金与材料工程学院，重庆 401331； 3. 重庆科技学院 机械与动力工程学院，重庆 401331)
摘 要: 采用光学显微镜、电子显微镜和动态力学分析等方法研究Bi含量对直径为400 μm、高度为200 μm的无铅Cu/Sn-0.3Ag-0.7Cu(SAC0307)/Cu微尺度焊点的显微组织及蠕变性能的影响。结果表明：当焊点中Bi含量较低(1%(质量分数))时，其基体组织细小，Cu6Sn5为粗大块状，Ag3Sn分布不均匀；当焊点中Bi含量较多(3%(质量分数))时，基体组织与Cu6Sn5进一步细化，Ag3Sn在细化的同时分布更均匀，界面扇贝状IMC层更平直。另外，温度为80~125 ℃、应力为8~15 MPa条件下，拉伸蠕变试验得到SAC0307微焊点的蠕变激活能(Q)和蠕变应力指数(n)分别为82.9 kJ/mol和4.35；当钎料中Bi含量由1.0%增加到3.0%时，焊点的Q值从89.2 kJ/mol增加到94.6 kJ/mol，n值由4.48增加到4.73，钎焊接头的抗蠕变能力明显提高，所有焊点的蠕变变形机制主要受位错攀移控制。
关键字: 电子封装；低银无铅钎料；微焊点；蠕变；力学性能
（1. State Key Laboratory of Mechanical Transmission, Chongqing University, Chongqing 400030, China; 2. School of Metallurgy and Materials Engineering, Chongqing University of Science and Technology, Chongqing 401331, China; 3. College of Mechanical and Power Engineering, Chongqing University of Science and Technology, Chongqing 401331, China）
Abstract:The microstructure and creep properties of Bi-doped Cu/Sn-0.3Ag-0.7Cu (SAC0307)/Cu micro-scale solder joints with diameter of 400 μm and height of 200 μm were investigated by optical microscope, scanning electron microscope and dynamic mechanical analysis method. The results show that adding 1% (mass fraction) Bi element into SAC0307 solder leads to the microstructural refinement, larger block of Cu6Sn5, non-uniform distribution of Ag3Sn and small primary β-Sn grains. While the SAC0307-3Bi solder joints contain relatively smaller sizes of primary β-Sn grains, also the IMCs appear much smaller than the examined joints with low Bi content. The IMC layer at the solder/Cu interface changes from a large up-and-down scallop shape to the straight one. In addition, the creep property of micro-scale solder joints was studied under 80-125 ℃ and 8-15 MPa. The activation energy (Q) of solder joints increase from 82.9 kJ/mol to 94.6 kJ/mol, the stress exponent (n) increases from 4.48 to 4.73 when Bi content increases from 1.0% to 3.0% (mass fraction), which indicates the increasing trends of the creep resistance and dominant deformation mechanism of dislocation climb.
Key words: electronic packaging; low-Ag lead-free solder; micro-scale solder joint; creep; mechanical property
