Cu／AuSn20／Ni焊点界面组织及剪切强度

Study of microstructure and shear strength of Cu/AuSn20/Ni joints

采用回流焊技术制备Cu／AuSn20／Ni（质量百分比）焊点，通过扫描电子显微镜及电子万能试验机分析焊点在300℃钎焊后的界面组织及剪切强度。结果表明，Cu／AuSn20／Ni焊点在300℃钎焊较短时间时，AuSn20焊料形成（Au5Sn＋AuSn）共晶组织，Cu／AuSn20上界面形成胞状的ζ-（Au，Cu）5Sn层；AuSn20／Ni下界面形成片状（Ni，Au）3Sn2金属间化合物（IMC）；随着钎焊时间的延长，基板中Cu、Ni原子不断往焊料扩散，焊料成分发生变化，冷却后焊点的共晶组织消失，上界面形成ζ（Cu）固溶体，下界面的片状（Ni，Au）3Sn2不断长大形成连续IMC层，焊点组织最终由℃（Cu）固溶体和（Ni，Au）3Sn2IMC组成。钎焊接头的剪切强度随钎焊时间延长而增大，但是增大幅度较小。

The Cu/AuSn20/Ni （mass percent） joint was prepared by the reflow bonding process, and the micro- structure and shear strength of the Cu/AuSn20/Ni joint were investigated. The results showed that, the solder formed a （AusSn＋AuSn） eutectic microstructure after reflow at 300℃ for a short time, and the cellular-like （Au,Cu）5 Sn intermetallic compound （IMC） was formed at the upper Cu/AuSn20 interface, while the flake-like （Ni,Au）3Sn2 IMC was formed at the lower AuSn20/Ni interface. Upon increasing the reflow time, more and more Cu（Ni）atoms from the suhtrates diffused into the solder, resulting the shift of chemical composition of the solder. So that the （Au,Cu）sSn phase at the upper Cu/AuSn20 interface transformed into the ζ（Cu） solid solution. The （Ni,Au）3Sn2 phase at the lower AuSn20/Ni interface grew gradually to form a continuous IMC layer. The eutectic microstructure in the solder vanished and the final microstructure of Cu/AuSn20/Ni joint was composed of the ζ（Cu） solid solution and （Ni,Au）3Sn2 IMC layer. The shear strength of the Cu/AuSn20/ Ni joint increased slightly with the increasing of the reflow time.