Investigation of Al-induced electroless cobalt-tin alloy deposition on Cu substrate

Cobalt-tin co-deposition was carried out on a Cu substrate by an electroless process where Al acts as a prime reducing agent. A second metal attached to the substrate, more electro-negative than the metal to be deposited, acts as an inducer, and film deposition proceeds due to the galvanic couple between the substrate and Al. The bath temperature was varied and ranged from room temperature to 90 degrees C, though improved deposit morphology was found around 80 degrees C. The pH and Sn/Co metal salt ratio in the bath solution were varied to observe the effect on the Sn/Co elemental ratio in the deposit. The deposits were examined by X-ray diffraction spectroscopy, scanning electron microscopy, and energy-dispersive spectroscopy to gain insight into the structure, surface morphology, and elemental composition. These ferromagnetic Co-Sn films could be an alternative to conventional chrome plating fabricated by a simple and economic deposition process.