基板间距对Cu/Sn58Bi-1.5Al2O3/Cu钎焊接头组织性能的影响

Effect of Substrate Distance on Microstructure and Properties of Cu/Sn58Bi-1.5Al2O3/Cu Solder Joint

采用回流焊工艺,制备不同铜基板间距的Cu/Sn58Bi-1.5Al_2O_3/Cu钎焊接头,并进行90℃×24 h的高温时效处理。通过界面微观组织观察、化学成分分析、拉伸性能检测和断口机理分析,研究基板间距对钎焊接头组织和性能的影响。结果表明：焊后,随着基板间距的增大,界面Cu_6Sn_5IMC层的厚度变小,解理台阶的宽度逐步减小,抵抗变形的能力提高。高温时效后,富Bi相组织由焊后的长条状转变为大的块状,界面原先呈扇贝状的IMC层增厚,凸起状变得平缓,并分为Cu_6Sn_5和Cn_3Sn两层金属间化合物。随基板间距的增大,焊后接头及高温时效后接头的抗拉强度均增大;相同基板间距下,与焊后接头相比,高温时效后的接头抗拉强度下降,拉伸断口的断裂位置由焊后的钎料部位变为钎料与Cu基板的交界处。硬脆的IMC层增厚和富Bi层的聚集这两个原因导致了接头失效。

The Cu/Sn58 Bi-1.5 Al_2O_3/Cu solder joints were prepared by using reflow soldering with different copper substrate distances, and the high temperature aging treatment of 90 ℃× 24 h of the solder joints were carried out. The effect of substrate distance on the microstructure and properties of the solder joint were studied through the observation of the interfacial structure, chemical composition analysis, tensile properties testing and fracture mechanism analysis. The results show that after welding, with the increase of substrate distance, the thickness of interfacial Cu_6 Sn_5 IMC layer decreases, the width of cleavage step decreases gradually and the ability to resist deformation strengthens. After the high temperature aging,the rich Bi phase changes from strip in weld state to large block, the original scallop-like IMC layer at the interface thickens,the convex shape becomes gentle, and the IMC layer is divided into the two intermetallic compounds of Cu_6 Sn_5 and Cn_3 Sn.With the increase of the substrate distance, the tensile strengths of the joints in weld and high temperature aging states increase. Compared with that of the welded joint, the tensile strength of the joint in high temperature aging decreases under the same substrate distance, and the fracture position of the tensile fracture changes from the solder after brazing to the junction of the solder and the Cu substrate. The thickening of the hard brittle IMC layer and the accumulation of the rich Bi layer lead to the failure of the joints.