Measuring the elastic moduli of electroless nickel-phosphorus deposits

A literature survey showed that reported values of Young's modulus ranged from 48 to 207 GPa (7 to 30 Msi) for high phosphorus (10% or more) electroless nickel (EN) deposits. This wide range seemed physically unrealistic. Moreover, the methods found in the literature for measuring the elastic moduli of metal plating were found to be difficult to use and prone to error. In this work, a simple and reliable way of measuring the elastic moduli of plated metal films is reported, and the Young's and shear moduli of a high phosphorus (10.5%) EN deposit are determined experimentally. It was found that the elastic moduli for the deposit in the as-plated condition, and when baked up to five hours at 190 degrees C (375 degrees F) in air, were essentially constant. The average measured Young's modulus was found to be 114 GPa (16.5 Msi), and the average shear modulus was 42.1 GPa (6.1 Msi). To prove the validity of the measurement technique employed here, the elastic moduli of electrodeposited nickel from a sulfamate bath were also measured, and good agreement was obtained between the measured values and those reported in the literature. The technique presented here is valid for measuring the elastic moduli of any desired metal plating or similar thin film material, and should be of particular value in measuring the properties of brittle deposits like EN.