Enhancement in the Deposition Behavior and Deposit Properties of Electroless Ni-Cu-P

Abstract

This work describes as an attempt to improve the deposit properties of electroless Ni-Cu-P deposits by controlling the deposition condition and the composition of the plating solution. Tensile internal stress induced by hydrogen evolution during electroless Ni-Cu-P deposition was manipulated by controlling deposition conditions such as stirring and zincating. The stirring action releases the hydrogen-induced stress and improves adhesion of the deposit in the condition of once zincate pretreatment. It was also attempted to vary the concentration of reducing agents (NaH 2 PO 2 ·H 2 O), buffering agents (NH 4 Cl), and complexing agents (Na 3 C 6 H 5 O 7 ·2H 2 O) of the plating solution to improve the deposition rate, crystallinity and the composition uniformity of Ni-Cu-P deposits. The results show that a decrease in complexing agents results in steadier deposition of Ni and Cu elements and higher deposition rate. The preferable deposition solution consists of 0.057 mol/L NiSO 4 ·6H 2 O, 0.0008 mol/L CuSO 4 ·5H 2 O, 0.14 mol/L NaH 2 PO 2 ·H 2 O, 0.07 or 0.09 mol/L Na 3 C 6 H 5 O 7 ·2H 2 O, and 0.75 mol/L NH 4 Cl at pH 8.0, which creates amorphous and uniform Ni-Cu-P deposits. © 2003 The Electrochemical Society. All rights reserved.