The effects of Bi doping on the electrochemical corrosion characteristics and dendrite growth behavior of lead-free Sn-3.0Ag-0.5Cu solder in 3.5% NaCl solution (mass fraction) were investigated by potentiodynamic polarization and AC impedance measurement. The surface morphologies and elemental compositions of various elements in the solder were determined by analyzing the corrosion product formed on the specimen using SEM and XRD techniques. The results show that the corrosion current density increases with increasing Bi content. However, the corrosion potential does not change regularly. All of impedances of Sn-Ag-Cu solder with and without Bi doping have the same characteristics, the equivalent circuit with two time constants can preferably fit the electrochemical impedance spectroscopy of Sn-Ag-Cu-χBi with error less than 5%, which shows that all electrochemical corrosion characteristics have similar regularities. The impedance arc radius decreases when the Bi content increases, which shows that anti-corrosion capacity decreases with increasing Bi content. The SEM results show that the dendrite growth due to electrochemical migration can be suppressed. XRD results show that the main contents on dendrite are Sn, Cu6Sn5, also tiny Bi and Ag3Sn.%采用动电位扫描和交流阻抗等方法研究Bi掺杂对Sn-3.0Ag-0.5Cu钎料在3.5％ NaCl(质量分数)溶液中电化学腐蚀性能及枝晶生长的影响；采用SEM和XRD技术分析其腐蚀形貌及成分.结果显示:随着Bi含量增加,腐蚀电流密度增大,但自腐蚀电位不呈规律性变化.阻抗谱显示:掺杂前后阻抗谱特征相同,均可用两个时间常数的等效电路模型表示,其拟合误差＜5％.随着Bi含量的增加,容抗弧半径减小,电荷传递电阻和腐蚀产物膜电阻均减小,耐蚀性能降低.SEM像显示,Bi掺杂对钎料在介质中电化学迁移速度有减缓作用,因而对迁移所致的枝晶生长具有抑制作用.XRD谱显示,枝晶主要成分为Sn和Cu6Sn5,同时伴有少量的Bi和Ag3Sn.
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