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This paper reports the co-deposition of Sn-Bi-Cu films using stannic salt bath which has good stability for up to a week. The effect of current density and bath stirring on the film composition and microstructure has been studied. The deposited films are rich in the more noble metal Bi at current densities up to 5 mA cm )2 but stabilize to about 49 wt. % Bi, 47 wt. % Sn and 4 wt. % Cu at 10 mA cm )2 and beyond, indicating the effect of limiting current density. There is improvement in the microstructure with stirring or aeration, but the film composition reverts to the Bi rich state, with close to 90 wt. % Bi for deposition at 5 mA cm )2 . This is attributed to the dispersion of Sn 2+ ions generated at the cathode during the two-step reduction of Sn 4+ ions, due to stirring. The bath is suitable for near eutectic compositions of Sn-Bi with <5 wt. % Cu content.

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We have developed a methane sulfonic acid (MSA) based ternary electrolytic bath for co-deposition of the eutectic Sn-Ag-Cu films. The bath contains thiourea (TU), which functioned as an effective chelating agent in controlling the bath stability as well as the elemental and microstructural properties of the deposited film. A study of the bath behaviour at TU concentrations in the range 0.06-0.2 M is undertaken with the help of elemental and microstructure analysis, cyclic voltammetry (CV) and impedance analysis. The deposited films have close to eutectic composition with slightly higher Cu content for all the TU concentrations. On the other hand, the microstructure is found to be increasingly refined with increasing TU content. The CV and impedance analysis confirm chelation of Ag and Cu with TU and absence of such chelation with Sn ions. It also indicates close deposition potentials for each metal ion. Impedance analysis specifically reveals presence of an adsorbed insulating film on cathode surface, contributed by MSA or water. It also reveals competitive deposition between the insulating film and metal ions.

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Today's high functionality electronic circuits require faster interconnection speed, better thermal conductivity and the good mechanical properties for reliability. These requirements calls for enhanced properties of the present solder materials. Appropriate reinforcements in the existing solder material will help in achieving much improved electrical, mechanical and thermal properties. Carbon Nano Tubes (CNTs) are one such material that can bring in considerable improvements in the properties of the solder material. CNT-Solder composite with less than 1% CNT is being explored for solder bumps in flip chip applications. This paper reports our work on co-deposition of CNT along with leadfree solder using electroplating process. For co-deposition of CNTs along with the solder, the processing of CNT is very important. Milling and CNT functionalisation are two such parameters that aid in its dispersion and make it active. The present studies include optimization of milling time for CNTs and selection of appropriate activators for functionalisation of CNTs in the electroplating bath.