(1. 重慶大學 機械傳動國家重點實驗室，重慶 400030； 2. 重慶科技學院 冶金與材料工程學院，重慶 401331； 3. 重慶科技學院 機械與動力工程學院，重慶 401331)
摘 要: 采用光學顯微鏡、電子顯微鏡和動態(tài)力學分析等方法研究Bi含量對直徑為400 μm、高度為200 μm的無鉛Cu/Sn-0.3Ag-0.7Cu(SAC0307)/Cu微尺度焊點的顯微組織及蠕變性能的影響。結果表明：當焊點中Bi含量較低(1%(質量分數))時，其基體組織細小，Cu6Sn5為粗大塊狀，Ag3Sn分布不均勻；當焊點中Bi含量較多(3%(質量分數))時，基體組織與Cu6Sn5進一步細化，Ag3Sn在細化的同時分布更均勻，界面扇貝狀IMC層更平直。另外，溫度為80~125 ℃、應力為8~15 MPa條件下，拉伸蠕變試驗得到SAC0307微焊點的蠕變激活能(Q)和蠕變應力指數(n)分別為82.9 kJ/mol和4.35；當釬料中Bi含量由1.0%增加到3.0%時，焊點的Q值從89.2 kJ/mol增加到94.6 kJ/mol，n值由4.48增加到4.73，釬焊接頭的抗蠕變能力明顯提高，所有焊點的蠕變變形機制主要受位錯攀移控制。
關鍵字: 電子封裝；低銀無鉛釬料；微焊點；蠕變；力學性能
（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
