钎焊工艺对Au-Sn/Ni焊点组织及力学性能的影响*

通过回流焊技术制备Au-Sn/Ni焊点，通过扫描电子显微镜和能谱检测分析钎焊接头的微观组织及其相组成，利用疲劳试验机对焊点的剪切强度进行检测，研究不同钎焊工艺对Au-Sn/Ni焊点组织和力学性能的影响。结果表明，在310 ℃钎焊1 min的Au-Sn/Ni焊点经过水冷或空冷后，焊料内部均形成镶嵌有离散分布的(Ni，Au)₃Sn₂相的(Au₅Sn+AuSn)共晶组织，焊料/Ni界面处形成(Ni，Au)₃Sn₂金属间化合物(intermetallic compound，IMC)层;钎焊后炉冷的焊点，由于冷却速度过慢，导致焊料中Ni质量分数增大，(Ni，Au)₃Sn₂相异常长大消耗共晶组织中的(Au，Ni)Sn相，焊料共晶组织消失。随着钎焊时间的延长，基板中的Ni原子不断往焊料扩散，界面处的IMC层厚度均有不同程度的增加。随钎焊时间延长焊点的剪切强度逐渐下降，而剪切断裂模式为脆性断裂，发生在焊料与金属间化合物层的界面处。Au-Sn/Ni焊点在310 ℃下钎焊1 min，并采用水冷方式时得到的力学性能最佳。

Influence of Reflow Process on Microstructure and Mechanical Property of Au-Sn/Ni Joints

The Au-Sn/Ni joints are prepared by the reflow bonding process,and the microstructure and phase composition are investigated by scanning electron microscope(SEM) with energy dispersive X-ray spectroscopy(EDS),the shear strength of the Au-Sn/Ni joint is detected by fatigue testing technology,the influence of the reflow process parameters on the microstructure and mechanical property of Au-Sn/Ni joint is researched.The results show that,the solder forms a (Au5Sn+AuSn) eutectic microstructure after soldering at 310 ℃ for 1 min with water-cooling and air-cooling,and the (Ni,Au)3Sn2 intermetallic compound (IMC) is formed and distributes in the solder matrix,while the (Ni,Au)3Sn2 IMC layer is formation at the AuSn20/Ni interface.However,as to the furnace-cooling joints,the mass fraction of Ni increases in the solder matrix due to the lower cooling rate.The (Ni,Au)3Sn2 grows abnormally due to the consuming of (Au,Ni)Sn phase,which leading to the disappearence of eutectic microstructure in solder matrix.The thickness of IMC layer increases gradually with extension of reflow time,because of the continually diffusion of Ni atoms from the substrate to solder matrix.The shear strength of the Au-Sn/Ni joints decreases slightly with the increasing of the reflow time,and the failure mold is brittle fracture at the solder/Ni interface.In a word,the Au-Sn/Ni joint gets the best mechanical properties by reflow at 310 ℃ for 1 min,with the water-cooling process.