期刊
出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.msea.2016.05.092
关键词
Sn57.6Bi0.4Ag solder; Nanoparticles reinforcement; Microstructure; Mechanical properties; Electromigration; Au embrittlement
类别
资金
- National Natural Science Foundation of China
- Research Grants Council of Hong Kong (NSFC/RGC) [N_CityU 101/12, 9054008]
Sn57.6Bi0.4Ag solder has been reinforced successfully through the addition of tungsten (W) nanoparticles at a concentration of 0.5 wt%. With the addition of W nanoparticles, the solder matrix lamellar interphase spacing was reduced by 31.0%. Due to the dispersion of W nanoparticles and the consequently refined microstructure, the mechanical properties of the solder alloy were enhanced, as indicated by a 6.2% improvement in the microhardness. During the reflow of solder on Au/Ni/Cu pads, the entire Au layer dissolved into the molten solder rapidly and a large number of (Au,Ni)(Sn,Bi)(4) particles were formed. The fracture path of the as-reflowed joint was within the solder region, showing ductile characteristic, and the shear strength was reinforced by 8.2%, due to the enhanced mechanical properties of the solder. During the subsequent aging process, the Au migrated back towards the interface and a thick layer of interfacial (Au,Ni)(Sn,Bi)(4) IMC was formed, leading to the shift of the fracture path to the interfacial IMC region, the transformation to brittle fracture and the deterioration of the strength of the joint, due to Au embrittlement. By adding W nanoparticles, the migration of Au was mitigated and the thickness of the (Au,Ni)(Sn,Bi)(4) layer was reduced significantly, which reduced the Au embrittlement-induced deterioration of the strength of the joint. During electromigration, the segregation of the Bi-rich and Sn-rich phases and the accumulation of the (Au,Ni)(Sn,Bi)(4) layer at cathode interface were mitigated by the addition of W nanoparticles, which improved the electromigration resistance. (C) 2016 Elsevier B.V. All rights reserved.
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