Phase Equilibria of Sn-Co-Ni System and Interfacial Reactions in Sn/(Co, Ni) Couples

Abstract

Sn-Co-Ni alloys of 25 different compositions have been prepared and equilibrated at 250°C. A new ternary (Ni, Co)Sn 4 phase is found, and all the binary compounds have very significant mutual solubilities between Co and Ni. According to the ternary equilibrium phase data and the constituent binary phase diagrams, the 250°C isothermal section of the Sn-Co-Ni system is proposed. In the Sn-CoSn-Ni 3 Sn 4 corner, there are nine two-phase regions and five tie-triangles. Interfacial reactions between molten Sn and Ni-1.0 at. pct Co, Ni-3.0 at. pct Co, Ni-5.0 at. pct Co, Ni-20.0 at. pct Co, and Ni-40.0 at. pct Co substrates are examined. It has been found that the interfacial reactions in Sn/Ni-1.0 at. pct Co are similar to those in Sn/Ni couples, and only the Ni 3 Sn 4 phase is formed. The (Ni, Co)Sn 4 phase is formed in the couples prepared with Ni-3.0 at. pct Co, Ni-5.0 at. pct Co, and Ni-20.0 at. pct Co substrates. It grows very fast and has a faceted and unique morphology.

Effects of Co Addition on Bulk Properties of Sn-3.5Ag Solder and Interfacial Reactions with Ni-P UBM

“…On the other hand, Chao et al reported interfacial reactions in Sn/(Co,Ni) couples at 250°C. 13 They reported that only one layer of Ni 3 Sn 4 IMCs is formed in the reactions of Sn/Ni-1at.%Co couples at 250°C, while two layers of (Ni,Co)Sn 4 and Ni 3 Sn 4 IMCs formed in the reactions of Sn/Ni-3at.%Co, Sn/Ni-5at.%Co, and Sn/Ni-20at.%Co couples. 13 In addition, the morphology of (Ni,Co)Sn 4 IMCs are plate-like.…”

“…13 They reported that only one layer of Ni 3 Sn 4 IMCs is formed in the reactions of Sn/Ni-1at.%Co couples at 250°C, while two layers of (Ni,Co)Sn 4 and Ni 3 Sn 4 IMCs formed in the reactions of Sn/Ni-3at.%Co, Sn/Ni-5at.%Co, and Sn/Ni-20at.%Co couples. 13 In addition, the morphology of (Ni,Co)Sn 4 IMCs are plate-like. 13 In this present work, the ternary compound Ni 22 Co 6 Sn 72 is similar to the (Ni,Co)Sn 4 IMC Fig.…”

“…13 In addition, the morphology of (Ni,Co)Sn 4 IMCs are plate-like. 13 In this present work, the ternary compound Ni 22 Co 6 Sn 72 is similar to the (Ni,Co)Sn 4 IMC Fig. 4.…”

“…Actually, a few studies have reported the existence of Co 3 Sn IMCs in the binary Sn-Co system. 12,13 Therefore, they are believed to be Co 3 Sn IMCs as a primary phase of solidification. Figure 3 exhibits the values of a Vickers hardness number (VHN) as a function of the Co content.…”

Co Solubility in Sn and Interfacial Reactions in Sn-Co/Ni Couples

“…5,7 Although it is obvious that knowledge regarding Co solubility in molten Sn at the Sn-rich corner is very important for better understanding of the effects of Co addition, there is only limited and even inconsistent information on Sn-Co phase equilibria in the literature. 6,[16][17][18] A second aim of this study is thus to determine Co solubility in molten Sn in the Sn-Co system at the Sn-rich corner.…”