Investigation On The Preparation Method And Properties Of SN-58BI Composite Solder

With the increment of humanistic concern of the environment, the appearance of relevant law and the promotion of markets, lead-free has become the popular current research on electronic packaging technology. Sn-Bi solder alloy, as one of the four lead-free kinds of solder alloy most likely to be replacement of Sn-Pb although with its low melting point and well wettability,the brittleness restrict the application in industry as lead-free. This article discusses the influence on the melting point and texture of Sn-58Bi lead-free solder alloy of 9A12O3·2B2O3 whiskers, La2O3 and Cu element, and discusses the texture evolution of the composite material and the interfacial IMC thickness growing regulation during the process of multi-remelting and aging. The transformation of IMCs grain feature during multi-remelting is analyzed. The changes of hardness of the composite are studied with the help of nano mark technology. Finally, the composite BGA spots'reliability is appraised by means of BGA shear test.The result shows: a small amount of reinforcement has little effect on the melting point of the solder alloy. The addition of 9A12O3·2B2O3 whiskers refines the texture of solder alloy, preventing the appearance of bulky phase rich in Sn; during the multi-remelting process, 9A12O3·2B2O3 reinforced Sn-58Bi composite solder alloy shows hollow polygonal, hollow strip and hollow hexagon prism Cu6Sn5 IMC, distributing in grain boundaries and restraining grain boundary shift thus grain growth; besides, with the addition of 9A12O3·2B2O3 whiskers, the texture refining can be restrained during the aging process. La2O3 can restrain the segregation and generation of bulky phase rich in Bi, making the texture uniform, and can restrain the IMC grain diameter coarsening after multi-remelting. The addition of 0.1% La2O3 restrains more effectively than 9A12O3·2B2O3 whiskers. With the addition of micrometer and nanometer Cu, refined structure can both be acquired in the solder alloy, while restraining coarsening of the solder alloy during the aging process, and nanometer Cu shows better refining effect; 1% nanometer Cu and micrometer Cu can also restrain IMC grain coarsening to some extent.Among the three kinds of composite solder alloy, 9A12O3·2B2O3 whiskers show the greatest influence on the performance of Sn-58Bi. The result of nano mark test shows that proper amount of 9A12O3·2B2O3 whiskers can increase the hardness of solder alloy. And BGA shear test shows:compared with Sn-58Bi/Cu bond, the composite solder BGA with 1.2% 9A12O3·2B2O3 whiskers can bear larger shear strength, and the shear strength stays fairly stable during the multi-melting process; meanwhile, the addition of 9A12O3·2B2O3 whiskers can increase the shear strength after high temperature aging. The observation of micro texture of the fracture sections shows, 9A12O3·2B2O3 whiskers can improve the bond reliability with load transmission, crack bridging, crack deflection, interface dissociation and extraction effect.