Study of Sn and SnAgCu Solders Wetting Reaction on Ni/Pd/Au Substrates

• Published in: Journal of electronic materials 2016-12, Vol.45 (12), p.6079-6085
• Main Authors: Liu, C. Y., Wei, Y. S., Lin, E. J., Hsu, Y. C., Tang, Y. K.
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Electronics and Microelectronics; Instrumentation; Lead free solders; Materials Science; Metals; Optical and Electronic Materials; Solid State Physics; Studies
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-016-4941-3

Wetting reactions of pure Sn and Sn-Ag-Cu solder balls on Au(100 Å and 1000 Å)/Pd(500 Å)/Ni substrates were investigated. The (Au, Pd)Sn 4 phase formed in the initial interfacial reaction between pure Sn and Au(100 Å and 1000 Å)/Pd(500 Å)/Ni substrates. Then, the initially formed (Au, Pd)Sn 4 compound layer either dissolved or spalled into the molten Sn solder with 3 s of reflowing. The exposed Ni under-layer reacted with Sn solder and formed an interfacial Ni 3 Sn 4 compound. We did not observe spalling compound in the Sn-Ag-Cu case, either on the thin Au (100 Å) or the thick Au (1000 Å) substrates. This implies that the Cu content in the Sn-Ag-Cu solder can efficiently suppress the spalling effect and really stabilize the interfacial layer. Sn-Ag-Cu solder has a better wetting than that of the pure Sn solder, regardless of the Au thickness of the Au/Pd/Ni substrate. For both cases of pure Sn and Sn-Ag-Cu, the initial wetting (