Sn-Zn-Ga-Pr钎料表面锡须的自发生长

Spontaneous growth of Sn whiskers on surface of Sn-Zn-Ga-Pr solders

结合扫描电镜与电子能谱分析了稀土元素对无铅钎料显微组织的影响.结果表明,当无铅钎料中的稀土添加过量,会诱发锡须在无铅合金表面的自发生长.在向Sn-9Zn-0.5Ga基体合金中添加0.7%(质量分数)的稀土元素镨(Pr)后,仅需室温时效12 h,合金组织中的稀土相表面即发生了锡须的自发生长.随着时效时间的延长,锡须会继续长大,其最终长度可达100μm.最后对过量稀土元素添加导致锡须生长的力学原因作了初步探讨,分析认为稀土相氧化所产生的微观压应力可能为锡须的生长提供了驱动力.

In spite of many beneficial effects obtained from the doping of rare earth（RE） to lead-free solders,it is newly found that an exceeded addition of RE would cause a risk of Sn whisker growth in the alloys.The results indicate that with the addition of 0.7% Pr to Sn-9Zn-0.5Ga solder,many Sn whiskers spontaneously grow from the surface of Sn-Pr phases in the bulk solder exposed for 12 hours only.And the whiskers show a continuous growth with the exposure time being increased.The final longest length of the whisker can reach 100 μm,which can lead to a serious reliability problem for electronic assemblies.Finally,the mechanical reason for whisker growth is discussed.