Improved Electro-migration Resistance in Nano Ag Modified Sn-58Bi Solder Joints under Current Stressing
In this study, doped-Sn58Bi solders were prepared by mechanically dispersing Ag nano particles additive in Sn-58Bi solders. The interfacial morphologies of the plain solder and doped Sn-58Bi solders under a direct current (DC) of 2.5 A at 75℃ temperature with Cu pads and Au/Ni/Cu on daisy chain type ball grid array (BGA) substrates were characterized. Unlike the plain solder, there is no obvious accumulation of Bi-rich IMC or Sn rich IMC extrusions on the anode side or cathode side, respectively. The Cu-Sn IMCs on the Cu substrate and Ni-Sn IMCs on the Au/Ni substrates were formed near the cathode interface after the first-reflow induced current crowding near the junction. Cluster like Ag-Sn IMCs in the solder matrix prevented the migration of atoms under current stressing and improved the electro-migration resistance. In addition, fracture occurs at the IMC interfacial region during shear testing with a ductile fracture mode. In the solder ball region β-Sn matrix of Sn-58Bi solder joints with a refined microstructure and inter-metallic compound particles Ag were observed, which resulted in an increase in the shear strength, due to a second phase dispersion strengthening mechanism.
Nano doping Flip Chip solder joints microstructure Electro-migration Shear strength
I. Shafiq Y.C. Chan
Department of Electronic Engineering City University of Hong Kong, Kowloon Tong, Hong Kong SA R
国际会议
西安
英文
391-396
2011-06-17（万方平台首次上网日期，不代表论文的发表时间）