Internal Stress Control of Nickel-Phosphorus Electrodeposits Using Pulse Currents

Nickel-phosphorus deposits with various phosphorus contents and internal stresses were electroplated from a nickel sulfamate bath without an additive by varying the duty cycle and frequency of the pulse current. A reduction in the duty cycle increased the phosphorus content and decreased the internal tensile stresses in the deposit. At a 0.1 duty cycle, a deposit with slightly compressive internal stress was produced. A deposit with a thickness of several hundred micrometers was plated at 0.1 duty cycle on a copper plate with good adhesion. Because the waveform parameters of the pulse current strongly affects the current efficiency and the microstructure of the deposit, the internal stress of the deposit as a function of the current efficiency, phosphorus content, and grain size was measured and discussed.