FORMATION OF INTERMEDIATE INTERMETALLIC LAYERS ON INTERACTION OF ELECTRODEPOSITED SN, NI-FE, NI-B COATINGS WITH DIFFERENT METALLIC SUBSTRATA

The structure of layers and formation of intermetallic phases after th ermal treatment in the system of thin electrodeposited Sn, Ni-Fe and s puttered Cu, Fe-Ni layers (thickness 0.1-2.0 mu m) and thick electrode posited Sn (thickness 6-10 mu m) and Fe-Ni and Ni-B layers (thickness 2 mu m) have been investigated by means of scanning electron microscop y (SEM), transmission electron microscopy (TEM), and by metallographic and X-ray diffraction (XRD) techniques. The formation of intermetalli c phases NiSn3, Ni3Sn2, FeSn2 and considerable reduction in the format ion of brittle layers Ni3Sn4, Cu6Sn5, Cu3Sn are determined by the stru cture 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 a s a result of thermal treatment at 170 degrees C up to 75 h. An amorph ous Ni-B layer [B 4-8; C (3-7) x 10(-2) wt%] prevents formation of Ni3 Sn4 and Cu6Sn5 in the system Sn/Ni-B/Cu (or Cu-Zn alloy) as a result o f thermal treatment at 130 degrees C (200 h) and 170 degrees C (150 h) .