Internal Stress of Ni-P Alloy Electroplating Films

Abstract

Internal stresses of electroplated Ni-P alloys and electrolytic hydrogen charging to the deposits were investigated using a spiral stress contract-meter technique. The current density increased the internal stress of the deposit, but the bath temperature decreased it. Internal stress depends on the P content of the Ni-P alloy deposits. Deposits containing more than about 20 at% P are stressed compressively, whereas those with lower P content undergo tensile stress. Effects of hydrogen penetration into and escape from deposits on the stress of Ni-P alloy deposited spirals were examined in terms of the electrolytic hydrogen charge, which led to classification into two groups. The first group showed great change of stress by the hydrogen charge and showed tensile stress under electrodeposition. The second group showed no change of stress by the hydrogen charge. They show compressive stress that depends on the hydrogen diffusion constant of the deposits. Hydrogen incorporation, its trapping in the deposits, and its subsequent escape under electrodeposition play important roles in the internal stress of Ni-P alloy electrodeposits.