Abstract
Watt’s nickel bath and nickel sulfamate bath are commonly applied for plating of micro-fabrication parts. In particular, the nickel sulfamate bath produces nickel plating with low residual stress and high tensile strength. Nickel sulfamate baths are therefore used extensively for electroforming and Micro Electro Mechanical Systems (MEMS). Boric acid is usually used as a pH buffering agent in the plating bath. However, boron-containing effluents are increasingly regulated because of environmental concerns. To solve these problems, organic acids such as acetic acid and citric acid were investigated as alternatives to boric acid. The pH buffering action of the organic acid baths was higher than that of the boric acid bath. Furthermore, the mechanical properties of nickel films obtained from a low-concentration nickel plating bath using an organic acid buffer were superior to those obtained from a bath buffered with boric acid. Nickel films with good mechanical properties were obtained from high-concentration nickel baths, which showed good pH stability even without a buffering agent in the formulation. Subsequent SEM and XRD analyses of these plating films revealed a defect free cantilever structure prepared with MEMS.
