Research On SnAgCu Solder Alloys

Abstract The EU has issued banning mandate which prohibit the use of lead and someother hazardous materials in home electronically instruments by 7/1/2006。Lead-freesolder research is in use stage. SnAgCu solder alloys have been regarded as the mostpromising alternative of SnPb solder alloys due to the excellent composite properties. SnAgCu solder alloys have two shortcomings comparing with SnPb solder alloys:one is its higher melting temperature; which made the process windows smaller; theother is its higher cost due to the use of silver. In this paper, SnAgCu solder alloys were researched through varying the wt% Agand Cu, and to test Ag and Cu wt% how to have effect on the melting temperature,and their spreading abilities. Then the author chose some of them to test theirmechanical properties and other performances, finally observed their microstructuresand analyzed in mechanism to determine the characters and regularity of the SnAgCuseries alloys. The result shows that the melting temperature of the SnAgCu is not moreapparent than expected. The melting temperature will increase with the decreasing ofthe Ag content under the condition of the Ag content less than 2.9wt%; but whileunder the condition of the content is more than 3.8wt%, the temperature range isabout zero, which shows that the alloying composition approaches to eutectic point,and with the variation of Cu content, the melting temperature changes a little. Theconduction capability of SnAgCu solder is prior to SnPb solder, and its mechanicalperformance is approached or prior to SnPb solders. The density is less about 10%than SnPb solder's, which is benefited to its promotion. Researches were made about the microstructure of SnAgCu solder alloy and itssolder joint. By analyzing interactions between elements in the alloy and the relevantbinary phase diagrams, it is concluded that the main components in SnAgCumicrostructure are the intermetallic Ag3Sn and Cu6Sn5 distributed on the base of Snmatrix.