Ag-Pd和Ni对无铅钎料焊点形状、微结构及剪切强度的影响

EFFECTS OF Ag-Pd AND Ni ON THE JOINT SHAPE, MICROSTRVCTURE AND SHEAR STRENGTH OF LEAD-FREE SURFACE MOUNT SOLDER JOINT

研究了器件端头两种不同的金属化层（Ａｎ－Ｐｄ和 Ｎｉ／Ａｎ－Ｐｄ）对 Ｓｎ－Ｓｂ钎料表面贴装焊点的形状、微结构及剪切强度的影响，并与常用的 Ｓｎ－Ｐｂ－Ａｇ钎料焊点进行了比较结果表明。 Ｓｎ－Ｓｂ／Ａｇ－Ｐｄ焊点由于 Ｓｎ－Ｓｂ钎料与 Ａｇ－Ｐｄ层在回流焊接过程中的剧烈反应导致钎料在器件端头区域集中而不在 Ｃｕ焊盘上充分铺展，焊点强度低，断裂发生在原 Ａｇ－Ｐｄ／陶瓷界面；Ｓｎ－Ｓｂ／Ｎｉ／Ａｇ－Ｐｄ焊点中 Ｎｉ有效地阻止了 Ａｇ－Ｐｄ在钎料中的溶解，焊点形状理想，强度很高；而对于Ｓｎ－Ｐｈ－Ａｇ饵料，器件金属化层对焊点形状和强度影响不大，剪切测试后，断裂发生在钎料内部．

The joint shape, microstructure and shear strength of 95Sn5Sb solder joints with dif- ferent terminal metallizations (Ag-Pd and Ni/Ag-Pd) of component were investigated with comparison to 62Sn36Pb2Ag solder joints. The results show that the drastic reaction between Sn-Sb solder and Ag-Pd leads to the solder not spreading entirely on the Cu pad but concentrating on the terminal of component. The shear strength of Sn-Sb/Ag-Pd solder joint is very low and the fracture occurs at the original interface of Ag-Pd/ceramic. The Ni layer in Sn-Sb/Ni/Ag-Pd solder joint effectively avoids the leaching of Ag-Pd to the solder so that a high strength solder joint with perfect shape is achieved. The terminal metallizations of components have little effect on the shape and the shear strength for Sn-Pb-Ag solder joint. Fracture occurs inside the Sn-Pb-Ag solder after shear test.