Study On Wettability Of Snagcu Lead-free Solder And Electromigration Of Solder Joint

Because of the harm of Pb to environment and bodies,at present the electronic -packaging materials don't contain lead basically. Solders are the main join materials in the electronic– packaging and now lead-free solders are used in the electrical products on a large scale.Though the lead-free solders correspond to SnPb on mechanical performance,electricity performance and worm performance, it's high price and bad wettability are becoming the important factors of blocking develepment of electrical products.At the same time along with the size and picth of solder joints becoming smaller and smaller, current density increases rapidly, the bump current density is now approaching 104A/cm2 level, the electromigration of solder joint will occur beyond the critical current density. Thus it is becoming a significant reliability issue before long. So it is very necessary to study the wettability of lead-free solders and electromigration of solder joints.In terms of wettability study on low Ag lead-free solders, the wettability performance of lead-free solders was evaluated by measuring the wetting angles and spreading area.In this paper SnAgCu solder alloys were researched through varying the wt% Bi and wt% Ag to test Bi and Ag how to effect on the lead-free solders wettability in different flux and temperature.The result shows that the wettability of Sn0.5Ag0.7Cu3Bi lead-free solder corresponds to one of Sn3.0Ag0.5Cu,moreover there is an advantage in the aspect of cost.On studying of electromigration on lead-free solder joints,the theories and the current studies on electromigration have been introduced firstly.Due to most of current electro- migration study focusing on Al and Cu interconnect,there is little electromigration study on solder joints under high current density. However the failure of electrical products by electromigrating must become a main failure mode for the packaging density is becoming more higher. So the electromigration study of soler joint possess high academic value and good market prospect. In this thesis, the straight U-groove experimental platform was set up with current density of 1.7×104A/cm2.The problem of heat diffusion was solved by a new way.In the aspect of electromigration study,firstly the (Interface Metal Compound) evolution of EM was researched along with times,including thickness and appearance.the change reasons of IMC were analyzed. At the same time the difference of their changs was studied between EM and no EM under the same temperature.Secondly the voids propagate was studied in cathode IMC.Lastly the mechanics performance of solder joints was analyzed by tensile test before and after EM, contrasting the fracture changes.