Transformation upon heating of electrodeposited metastable tin-nickel alloys, prepared from pyrophosphate baths, was studied by means of differential thermal analysis and X-ray diffraction. Metastable tin-nickel alloys were obtained as a single phase (NiSn) in the composition range from 40 to 55at.% Sn. Alloys containing 49-55at.% Sn were transformed exothermically into mixed or single equilibrium phases of Ni₃Sn₂+Ni₃Sn₄ or Ni₃Sn₄. Tin-nickel alloys with higher tin content had lower transformation temperature; e.g., they were transformed at below 100°C for 55at.% Sn, whereas at 340°C for 49at.% Sn. Tin-nickel alloys containing 40-44at.% Sn were transformed to a single phase of Ni₃Sn₂ at ca. 300°C with no distinct heat evolution, corresponding to the transformation. Tin-nickel alloys (47at.% Sn) electrodeposited from fluoride baths were transformed at 360°C into another supersaturated metastable phase. The intermediate metastable phase was decomposed into mixed equilibrium phases of Ni₃Sn₂+Ni₃Sn₄ at 600°C.

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The electroless tin plating bath containing Ti³⁺ as a reducing agent which has been newly developed by M.E. Warwick et al. does not have desirable stability. We found the addition of NTA to the bath can eliminate the deposition in a suspended form and we determined the optimum compositions of NTA containing bath. The role of three chelating agents added to the bath, namely, citrate, EDTA and NTA was discussed on the basis of absorption spectra data of the bath.

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An electroless nickel plating on ceramics have been studied using α-Al₂O₃ and piezo-electric ceramics. Etching and catalizing steps indicated important role to obtain good adhesion. Etching with hot HCl followed by sensitising with SnF₂ showed highest adhesion (>120kg/cm) on the piezoelectric ceramics. Ion micro analysis and SEM photomicrographs revealed that SnF₂ solution may contribute to etching and sensitising the ceramics. Conventional etching treatments had no measurable effect on adhesion of α-Al₂O₃ ceramics. However, sensitising with SnF₂ followed by two successive activation showed good adhesion. Furthermore, adhesion was increased after heat treatment. This metallization also provided reliable electric properties.

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Copper films were prepared by chemical plating from the baths containing EDTA or Quadrol as a complexing agent and the effects of 2, 2′-bipyridyl and potassium hexacyanoferrate (II) on the mechanical properties of the copper deposits were studied in detail. Fatigue Ductility Flex Tester was employed for evaluating the fatigue ductility of the copper films. Factors affecting fatigue ductility of the copper films were discussed on the basis of crystallographic features of the deposits. The addition of 2, 2′-bipyridyl and potassium hexacyanoferrate (II) in the chemical plating baths resulted in an increase in the elongation and fatigue ductility of the copper films, because strain-free copper deposits having larger crystallite size were formed. The best fatigue ductility can be obtained from the EDTA bath containing 20mg/l 2, 2′-bipyridyl and 20mg/l potassium hexacyanoferrate (II). In general, the harder deposit having the larger ultimate tensile strength was found to be composed of smaller crystallite. It was concluded that the fatigue life of the copper films was improved by the increase in fatigue ductility and the ultimate tensile strength.

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