The role of bi 3+-complei Ion as the stabilizer in electroless nickel plating process

Abstract

Bi 3+ -complex ion is presented here as a less toxic stabilizer for use in electroless nickel plating (ENP) to replace the existing PlX 2+ ion stabilizer. The asymmetric derivatives of EDTA are identified to be a type of coordination ligands that can combine with Bf 3+ ions to form soluble complexes in the acidic ENP solution. In the ENP system studied the Bi 3+-complex ion displays a critical stabilizer concentration of about 10 -5 mollL, that is, the percolation concentration over which the ENP rate drops sharply. Besides the experimental measurement, deposition rates of both Ni and P are also simulated by using a kinetic model that has been derived from the double electric layer theory. The Bi 3+-complex ion, behaving like conventional Pb 2+ ion, stabilizes ENP bath through the chemical replacement reaction at the surface of Ni deposition layer and results in a. passive plating surface. This investigation also verifies the properties of the EN deposit, which are insignificantly affected by the length of service time of the plating solution by employing Bf 3+ complex ion stabilizer. © 2009 American Institute of Chemical Engineers.