Design And Study On Properties In Sn-Based High Multicomponent Temperature Lead-Free Solders

Nowadays,Sn-95Pb(wt.%) and Sn-80Au(wt.%) are high temperature solders in semiconductor stage-packaging technology.But their applications are limited because of their disadvantage of pollution and fantastic price.At present,the method of "try and error" was always used to search for the best alloying composition of soldering alloys,which squanders manpower and material resources and makes research cycle long.With the design system of lead-free solder(ADMIS) and combining CALPHAD method,the new high temperature lead-Free solders of Sn-Sb-Cu-Ag and Sn-Ag-Au welding alloys were designed and studied.By testing and analysing,we acquired their physical and chemical properties,electrical and heat properties.At the same time,We researched on the work of interfacial reaction on solders and the substrate..The main contents of this thesis are as follows:(1) With the CALPHAD method and DSC experiment,two kinds of high temperature lead-free solders,Sn-Sb-Cu-Ag and Sn-Ag-Au welding alloys,the best composition of Sn30Sbl3CullAg(wt.%) and Snl0Ag40Au(wt.%) with the best melting points were designed.Their melting points are 298.7℃-321.8℃and 295.8℃-324.8℃.(2) The addition of Ag can reduce the melting temperature range of Sn-Sb-Cu alloy and increases the wettability on the Cu substrate.When 0.3%Ce is added,the best porperties of wettability and electroconductivity can obtained.Besides,the antioxidativity of this alloy is also excellent.(3) The wettability of Sn-Ag-Au alloy and the Cu substrate is excellent both in the absence of Oxygen and Oxygen condition and its wetting angle is smaller than 20 degree.The properties of micro-hardness and electroconductivity of the Sn-Ag-Au alloys are the same with those of Sn-Sb-Cu-Ag alloys.Similarly in antioxidativity,the Sn-Ag-Au alloys is very excellent.It is cheaper than Sn-80Au(wt.%) alloy. (4) Interfacial reactions on Sn-Ag-Au alloy and the Cu substrate was investigated by the shearing test and aging heat treatment,and we concluded that the best reflowing time is 1min,and the first precipitation phase is Cu₃Sn.The shear strength is the greatest of the interface between Sn-Ag-Au solder and Cu substrate in 240℃.