研究了SnAgCu焊料与铜基的接头在150℃等温时效后,接头界面金属间化合物的形成与转变。用扫描电镜观察在时效过程中焊接接头的显微组织演变。用X射线能谱仪测定了化合物的成分。结果表明,回流焊接时,在焊料和铜基板之间形成了Cu6Sn5化合物层,随着时效时间的增加,Cu6Sn5的晶粒大小逐渐增加,并且形态逐渐从扇贝状依次转变为针状和杆状,最后转变为颗粒状。与此同时,在焊料及Cu6Sn5金属间化合物层之间形成了杆状的Ag3Sn。焊接接头的抗拉强度的测量表明,抗拉强度随着时效时间的增加开始略有增加而后逐渐下降。断口观察发现,随着时效时间的增加,断裂源从焊料内部向Cu6Sn5界面移动。在化合物层界面发生的断裂是由于化合物晶粒粗化和Cu6Sn5化合物层厚度的增加造成的。

The formation and evolution of the intermetallic compound (IMCs) between SnAgCu lead-free solder and Cu substrate,after isothermal aging at 150℃,were studied. Scanning electron microscope (SEM) was used to observe the microstructure evolution of solder joint during aging. The IMC phases were identified by energy dispersive X-ray (EDX). The results showed that IMCs layer of Cu6Sn5 was formed at the interface of solder and Cu during reflowing. With the increase of aging time,the grain size of the interfacial Cu6Sn5 increased and the morphology of the interfacial Cu6Sn5 column was changed from scallop-like to needle-like and then to rod-like and finally to particles. At the same time,the rod-like Ag3Sn phase formed at the interface of solder and the IMCs layer of Cu6Sn5 with the aging time increased. In addition,large Cu6Sn5 formed in the solder with the aging time increased. The tensile strength was measured for the solder joints. The results showed that the tensile strength increases slightly at beginning and then decreases with the aging time. SEM was used to observe the fracture surface and it showed that the fracture position moved from solder matrix to the interfacial Cu6Sn5 IMCs layer with the aging time increased. The weakening of the solder matrix is caused by the coarsening of the eutectic solder structures. The weakening of the interfacial IMCs layer is caused by the evolution of morphology and size of the interface Cu6Sn5 layer.