钎料熔滴与焊盘界面反应及再重熔时的界面组织演变

采用熔滴直接凸点制作方法,对共晶SnPb及SnAgCu钎料熔滴与Au/Ni/Cu焊盘所形成的凸点/焊盘界面组织进行了研究,并与激光重熔条件下获得的凸点/焊盘界面组织进行了比较,考察了凸点/焊盘界面组织在随后的再重熔过程中的演变.结果表明:钎料熔滴与焊盘在接触过程中形成了Au-Sn化合物,Au层并未完全反应.在随后的再重熔过程中,Au层被完全消耗,全部溶入钎料基体中,Ni层与钎料发生反应.无铅钎料(SnAgCu)和SnPb钎料所形成的界面组织明显不同;再重熔后SnPb钎料/焊盘的界面组织为Ni3Sn1,SnAgCu钎料/焊盘界面组织为(CuxNi1-x)6Sn5.

Interface reaction of solder droplet/pad and intermetallic compounds evolution during reflow soldering

The interface structures of solder droplet for SnPb and SnAgCu Al/Ni/Cu pad were investigated by droplet direct laser fabrication method,which is compared with the interface structures for bump and pad under laser reflow bumping.The intermetallics evolution at solder bump/pad interface during subsequent reflow soldering is conducted.The results show that,during the contact reaction between molten solder droplet and pad,Au is dissolved into molten solder droplet and Au-Sn intermetallic compounds are precipitated,while Au doesn't react with solder droplet fully.During the subsequent reflow soldering,Au layer disappears from the interface,Au-Sn compounds are distributed into solder matrix,and Ni layer is exposed to solder and reacts with solder directly.Distinctive difference exists between the intermetallics formed at Pb-free solder/pad interface and SnPb solder/pad interface during reflow soldering process.For the SnPb solder/pad system,the Ni_3Sn_4 layer is formed at the solder/pad(interface) during reflow.For the SnAgCu solder/pad system,the(Cu_xNi_(1-x))_6Sn_5 layer is formed at the solder/pad(interface) during reflow.