Sn-Ag-xCu-Bi-Ni/Cu焊点界面IMC演变

为了研究低银无铅焊点界面金属间化合物(IMC)的形成与演变,以低银无铅焊点Sn-Ag-xCu-Bi-Ni/Cu为研究对象,研究了钎料中Cu质量分数对界面IMC厚度、形貌和成分的影响.实验结果表明,随着钎料中Cu质量分数的增加,回流焊后焊点IMC层厚度变薄,IMC晶粒尺寸增大,IMC晶粒形貌由颗粒状转变为棱柱状以及鹅卵石状,同时界面IMC成分发生由(Cu,Ni)6Sn5向Cu6Sn5的转变.高温时效后,界面IMC层厚度增长.当钎料中Cu质量分数超过1%时,时效后生成较厚的Cu3Sn化合物层,对焊点可靠性不利.钎料中Cu质量分数应控制在1%以下.

Evolution of the Interfacial IMC in Sn-Ag-xCu-Bi-Ni/Cu Solder Joints

In order to study the formation and evolution of the intermetallic compounds（IMC） in low-Ag lead-free solder joints,the effect of Cu content on the thickness,morphology,and constituent of the interfacial IMC in Sn-Ag-xCu-Bi-Ni/Cu solder joints was investigated.Experimental results indicated that the thickness of IMC layer decreased but the grain size of which increased as the concentration of Cu increased in the solder alloys.Meanwhile,the appearance of IMC grains transformed from tiny grains to prisms and cobbles,and the constituent of IMC transformed from（Cu,Ni）6Sn5to Cu6Sn5.The thickness of IMC layer increased during high temperature storage（HTS） aging.Thick Cu3Sn layer formed during aging when the Cu content was higher than 1% in the solder.Due to reliability concern,the content of Cu in the solder should be controlled less than 1%.