Interfacial microstructure between Sn-3Ag-xBi alloy and Cu substrate with or without electrolytic Ni plating
Authors: Hwang, Chi-Won; Lee, Jung-Goo; Suganuma, Katsuaki; Mori, Hirotaro
Source: Journal of Electronic Materials, Volume 32, Number 2, February 2003 , pp. 52-62(11)
Abstract:The microstructure of the interfacial phase of Sn-3Ag-xBi alloy on a Cu substrate with or without electrolytic Ni plating was evaluated. Bismuth additions into Sn-Ag alloys do not affect interfacial phase formations. Without plating, -Cu6Sn5/ε-Cu3Sn interfacial phases developed as reaction products in the as-soldered condition. The -phase Cu6Sn5 with a hexagonal close-packed structure grows about 1-µm scallops. The ε-phase Cu3Sn with an orthorhombic structure forms with small 100-nm grains between -Cu6Sn5 and Cu. For Ni plating, a Ni3Sn4 layer of monoclinic structure formed as the primary reaction product, and a thin -Ni3Sn2 layer of hexagonal close-packed structure forms between the Ni3Sn4 and Ni layer. In the Ni layer, Ni-Sn compound particles of nanosize distribute by Sn diffusion into Ni. On the total thickness of interfacial reaction layers, Sn-3Ag-6Bi joints are thicker by about 0.9 µm for the joint without Ni plating and 0.18 µm for the joint with Ni plating than Sn-3Ag joints, respectively. The thickening of interfacial reaction layers can affect the mechanical properties of strength and fatigue resistance.
Document Type: Research Article
Affiliations: Email: firstname.lastname@example.org
Publication date: 2003-02-01