Abstract
Electroless Pd-P plating using sodium hypophosphite as a reducing agent has been investigated. From fundamental experiments, triethylenetetramine (trien) was found to be much preferable complexing agent to the palladium ions. High bath stability can be achieved by an addition of thallium (I) sulfate to the bath. Plating rate is increased with increasing palladium ion concentration, but the other parameters such-as pH value, thallium ion and trien concentration do not have great influence on the plating rate. It was confirmed that phosphorus content of the deposited film decreases with increasing pH value of the bath. Deposited film has amorphous structure under the as-plated condition and it is transformed into the crystals consisting of Pd and Pd8 P by heating at 300°C for 2h. Physical properties such as solderability, contact resistance, sliding friction, hardness, stress and corrosion resistance were greatly improved by an addition of maleic acid to the bath.
