Interfacial reaction between molten Sn-Bi based solders and electroless Ni-P coatings for liquid solder interconnects
journal contributionposted on 22.10.2008, 14:13 by Jianfeng Li, Samjid H. Mannan, Mike P. Clode, Keming Chen, David C. Whalley, David A. Hutt, Paul ConwayPaul Conway
This paper reports on the interfacial reactions and lifetime of electroless Ni-P coatings in contact with molten Sn-Bi based solders. A layer of approximately 4 m thick electroless Ni-P in contact with the molten Sn-58Bi solder began to fail at 48 h at temperatures between 200 C and 240 C. Elemental additions to modify the solder, included 1–2wt.% of Al, Cr, Si, Zn, Ag, Au, Ru, Ti, Pt, Nb, and Cu. Of these, only Cu modified the interfacial intermetallic compound growth from Ni3Sn4 to (Cu,Ni)6Sn5, resulting in significantly decreased consumption rates of the Ni-P substrate in contact with the molten solder and increasing the lifetime of the Ni-P layer to between 430 and 716 h. Micro cracks were observed in all but the thinnest Ni-P layers, allowing the solder to penetrate.
- Mechanical, Electrical and Manufacturing Engineering