微量元素添加对多元Sn-Bi系焊料合金组织与性能的影响

传统焊料合金由于熔点温度高,不能满足部分有机基板、温度敏感器件以及3D封装等多层封装形式的低温封装要求。以Sn-Bi合金为基体,通过添加微量Ag、Cu、Co和Ni元素形成新型多元合金,对多元合金的熔化性能、润湿性能、微观组织和力学性能进行研究。结果表明:微量元素的添加(质量分数0~1%)对多元Sn-Bi系合金的固相线温度影响很小,降低了SnBi57AgCuCo合金的液相线温度和熔程;添加微量元素降低了合金的表面能,提高了润湿性;多元Sn-Bi系合金的微观组织由SnBi共晶组织、β-Sn相和块状富Bi相组成,微量元素的添加细化了β-Sn相中的Bi相颗粒。组织中的金属间化合物颗粒提高了多元Sn-Bi系合金抗拉强度和延伸率;断口形貌表明合金主要沿Bi相晶界断裂,Bi相的细化可改善焊料合金的力学性能。

Effects of Addition of Trace Elements on the Structure and Properties of Multicomponent Sn-Bi Based Solder Alloys

Due to the high melting temperature,traditional solder alloys cannot meet the lowtemperature packaging requirements of some organic substrates,temperature-sensitive devices and multilayer packaging type,such as 3D packaging.The Sn-Bi alloy was used as the matrix to form new type multicomponent alloys by adding trace amounts of Ag,Cu,Co and Ni.The melting property,wettability,microstructure and mechanical property of the multicomponent alloy were studied.The results show that the addition of trace elements(the mass fraction of 0-1%)has slight effect on the solidus temperature of the multicomponent Sn-Bi based alloy,and reduces the liquidus temperature and the melting range of the SnBi57 AgCuCo alloy.The addition of trace elements reduces the surface energy of the alloy and improves the wettability.The microstructure of the multicomponent Sn-Bi based alloy consists of SnBi eutectic structure,β-Sn phase and bulk Bi-rich phase.The addition of trace elements refines the Bi phase particles in theβ-Sn phase.The intermetallic compound particles in the structure improve the tensile strength and elongation of the multicomponent Sn-Bi based alloy.The fracture morphology indicates that the alloy mainly fractures along the grain boundary of the Bi phase.The refinement of the Bi phase can improve the mechanical property of the solder alloy.