Study Of A Novel Zn Based High Temperature Pb-free Solder

Pb-rich solders such as85Pb15Sn have always been playing a significant role inhigh-temperature lead-free solder. Lead and lead compounds have been one of themost damaging chemicals to humanity body and the environment in17elementswhich were listed by Environmental Protection Agency (EPA), so lead-free has beenan inevitable trend in electronic products. It’s become a hotspot of researching the newenvironmentally friendly lead-free solder to replace the traditional Pb-rich solderalloys in recent years.Zn20Sn high temperature lead free solder has appropriate melting range, goodheat/electrical conductivity and low cost, while Zn4Al3Cu solder has highsolderability, small electrical resistivity and good mechanical property. The impact ofthe addition of Cu and Sn on physical properties, wetting ability, mechanical propertyand corrosion resistance of Zn20Sn and Zn4Al3Cu solder alloys is investigated,respectively, through adding Cu, Al and Sn into Zn solder matrix forming ternarysystem or multielement solder alloys to get the most optimized solder alloy. Theresults show that:The melting point and liquid temperature of the Zn20SnxCu solder alloysdecrease while the liquid-solid temperature range becomes narrow with the increasingof the addition of Cu (less than8%). The melting point of Zn20Sn6Cu is372.4℃, theliquid-solid temperature range of that is20.6℃. When the addition of Cu is more than6%, the density of the solder is large and conductivity drops marked. The addition ofCu can improve tensile strength obviously. Tensile strength of Zn20Sn solder alloy is80.4MPa. Tensile strength of Zn20Sn4Cu solder alloy is180.1MPa which is about1.25times than that of the matrix solder. When the addition of Cu is lower than4%,the corrosion potential of the Zn20SnxCu solder alloys is rising with increasing of theaddition of Cu, and corrosion rate goes down, consequently, corrosion resistanceenhances. When the addition of Cu is4%, Zn20Sn4Cu solder has the overallperformance with melting point380.4℃, spreading area51.3mm2, tensile strength 180.1MPa, corrosion potential-1.1785V, corrosion rate0.079mm/a.With the Sn addition increasing, the melting point, solid temperature and liquidtemperature of the Zn4Al3CuxSn solder alloys decrease while the liquid-solidtemperature range becomes narrow. When Sn additions are10%and15%, the meltingpoints of solder reach378.6℃and371℃, respectively, which meets demanding target.Density and resistivity of the Zn4Al3CuxSn solder alloys descend with the increasingof Sn addition. The resistivity of the Zn4Al3Cu10Sn solder is0.97×10-6.m which isapproximately34.9%smaller than that of the matrix solder. The spreading area ofZn4Al3CuxSn is rising by adding Sn into Zn4Al3Cu solder. The spreading area ofZn4Al3Cu10Sn reaches to the maximum value98.3mm2. The tensile strength of theZn4Al3CuxSn solder alloys is improving with increasing of the addition of Sn whichis more than5%. The tensile strength of Zn4Al3Cu10Sn reaches201.1MPa. Therefore,taking consideration of those properties of the novel solders, the best addition of Sn isabout10%.