Formation of intermediate intermetallic layers on interaction of electrodeposited Sn, Ni-Fe, Ni-B coatings with different metallic substrata

Abstract

The structure of layers and formation of intermetallic phases after thermal treatment in the system of thin electrodeposited Sn, Ni-Fe and sputtered Cu, Fe-Ni layers (thickness 0.1-2.0 μm) and thick electrodeposited Sn (thickness 6-10 μm) and Fe-Ni and Ni-B layers (thickness 2 μm) have been investigated by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and by metallographic and X-ray diffraction (XRD) techniques. The formation of intermetallic phases NiSn3, Ni3Sn2, FeSn2 and considerable reduction in the formation of brittle layers Ni3Sn4, Cu6Sn5, Cu3Sn are determined by the structure and purity of electrodeposited tin [C (0.5-5) x 10-2; N (1-5) x 10-2; Fe, Cu, Bi, Pb (0.15-5.0) x 10-2 wt%] in the system Sn/Fe-Ni/Cu. Electrodeposited Fe-Ni (80% Ni) as barrier layer in the system Sn/Fe-Ni/sputtered Cu completely prevents formation of Cu6Sn5, Cu3Sn as a result of thermal treatment at 170°C up to 75 h. An amorphous Ni-B layer [B 4-8; C (3-7) x 10-2 wt%] prevents formation of Ni3Sn4 and Cu6Sn5 in the system Sn/Ni-B/Cu (or Cu-Zn alloy) as a result of thermal treatment at 130°C (200 h) and 170°C (150 h).