Study On Preparation Process Of Ag-Cu-Ge Solder Alloy By Electromagnetic Powder Compaction

Silver based solders which have good wettability,high temperature resistance,corrosion resistance and high mechanical strength,have a broad application prospect in microelectronics packaging,military manufacturing,machinery manufacturing and chemical industry.But traditional medium temperature silver filler metals often add cadmium and other harmful elements to enhance the performance of solder.At present,for the sake of environmental protection,much attention has been paid to develop silver based solder without cadmium.But now there are few kinds of no cadmium silver based solder whose melting temperature ranges from 500?to650?.Existing research has shown that the melting point of Ag-Cu-Ge alloy solder is moderate?500⁶00??and its welding performance is excellent.Therefore,it has potential application in microelectronics packaging.But the solder is difficult to be processed into sheets because of the brittle phases such as germanium and intermetallic compounds??-Cu₅Ge₂?included it.Aimed at Ag-25Cu-24Ge solder chips forming difficulties,this topic adopts a method of electromagnetic compaction combined with powder metallurgy sintering process to prepare Ag-25Cu-24Ge eutectic alloy sheet.This method can not only avoid the poor processability of solders prepared through traditional methods,but also simplify the process and improve the yield.Firstly,the metal powder mixes were compressed under the reasonable voltage.Then,liquid phase sintering was conducted,also,aging treatment was carried on aiming at the compact edge warp.Finally,welding experiments were conducted on the solder chips prepared through the optimal process.The effects the preparation process has on the solder properties and welding properties were analysed comprehensively.The electromagnetic compaction experiment results show that the compaction density increased with the compaction voltage.When the compaction voltage reaches2800V,the compaction density is the highest.At the voltage of 3000V,cracks and even fractures develop in the internal of germanium powder particles.The sintering experiment results show that elastic aftereffect appeared in sintered body under low sintering temperature.And the density maximizes under 400?sintering temperature and 30min sintering time.As the temperature continues to rise,the coarsening phenomenon appears.Above all,the optimal compaction and sintering process parameters are obtained?2800V compaction voltage,400?sintering temperature,30min sintering time?.After 10h aging treatment under 150?,the buckling phenomenon is eliminated;its density is further improved;microstructure is more homogeneous;pores reduce;melting range narrows;resistivity decreases;germanium phase segregation weakens and more intermetallic compounds are generated.Finally,the optimal preparation process of solder is 2800V compaction voltage,400?sintering temperature,30min sintering time,10h aging time and 150?aging temperature.Solder chips prepared through the optimal electromagnetic compaction process were welded the copper plate and nickel.The welding experiment results show that the weld microstructure is homogeneous when the welding temperature is 600?.Also,no segregation and coarse grain develop.And,when the parent metal is nickel plate,the welding transition layer is thicker than that in copper plate,shows embedded structure,and have higher bond strength.Comprehensively,Ag-25Cu-24Ge solder alloy sheet whose performance and welding quality meet requirements can be prepared through electromagnetic compaction combined with powder metallurgy sintering process.Meanwhile,this research solves the difficulties in processing forming and provides a theoretical guidance for the development of environmental protection medium temperature silver filler metals.