Research On SnBixIn Series And SnBiInSb (Ge, Ga, Ag) Series Solders

Sn-40Bi-xIn three element brazing filler metal and Sn-Bi-In-Sb-X(Ge,Ga,Ag)mutil-component alloys were studied in this paper.The alloy ingots were prepared by high temperature melting furnace.The microstructure,phase composition,mechanical properties and brazing joint microstructure of the alloy were studied by various analysis and testing methods.With the increase of In content,BiIn phase appeared in Sn-40Bi-xIn alloy except for the ?-Sn phase and Bi-rich phase.The microstructure is composed of Sn-rich phase,Bi-rich phase,and eutectic structures of Sn-rich and Bi-rich phase.The microstructures of Sn-40Bi-6In and Sn-40Bi-8In alloy are SnBi eutectic + BiIn-Sn eutectic +(Bi + ?-Sn),and the final microstructure is composed of ?-Sn + BiIn + Bi.At room temperature,the tensile strength and fracture strain curves first increase and then decrease with the increase of In content.The tensile strength decreases with increasing temperature from 60°C,80°C,100°C and 120°C,and is lower than that at room temperature.When the temperature exceeds 120?,the Sn-40Bi-6In and Sn-40Bi-8In alloys lose their loading capacity.The spreading area of brazing filler metal increased obviously with the increase of In content.Among the solder with different contents of In,the wetting effect of Sn-40Bi-8In solder is the best.The melting point of the Sn-Bi-In-Sb-Ga alloy is 75°C,the melting zone is 125°C,the melting point of Sn-Bi-In-Sb-Ge and Sn-Bi-In-Sb-Ag alloy is 200°C,the melting zone of the former is 75°C,and the melting interval of the latter is 100 °C.The phase structure of Sn-Bi-In-Sb-Ge alloy did not change under the condition of water cooling and furnace cooling,they are Birich solid solution phase,SbBi and InSb compound phases.Only InBi compound phase was detected in Sn-Bi-In-Sb-Ga high entropy alloy under water cooling condition,and Sn-Bi-In-Sb-Ag alloy was composed of InSb,Ag3 In and Sn phases.After slow cooling,the Bi solid solution phase and InSb compound disappeared in Sn-Bi-In-Sb-Ga high entropy alloy,Bi-rich solid solution phase and the SnBi compound were replaced by Ag3 In and Sn phase in Sn-Bi-In-Sb-Ag high entropy alloy.This indicates that the phase composition of Sn-Bi-In-Sb-Ga and Sn-Bi-In-Sb-Ag alloys are more sensitive to cooling rate.The wetting properties of Sn-Bi-In-Sb-X alloys were compared with those of three addition elements,and the wettability of Sn-Bi-In-Sb-Ag solder was the best.In ths study,with the higher the content of In element,the brazing effect of Sn-40Bi-xIn solders is better.When the In content is 8%,the edge of the brazing seam is smooth and well bonded,and the brazing effect is the best.After brazing,a Cu-rich transition layer is found on the side of the welding interface of SnBiInSbGe and SnBiInSbAg solders,and the diffusion of the filler metals and the parent material Cu is obvious.In comparison,the solder performance of SnBiInSbAg solder is the best.