Development of a Real-time Measurement Device for Monitoring the Internal Stress During Electroplating

In this study, we proposed a new real-time internal stress measurement design based on bending deformation of electroplated specimen. The volume change of fluid compartment caused by bending deformation of specimen on the wall was measured by fluid column height in a glass tube, and then the variation of internal stress could be calculated according to the Stoney formula. There are many factors that can cause variations during measurement, such as capillary action in glass tube, temperature of electrolyte, and clamped boundary condition of specimen. Their effects in measurement were taken into account and compensated accordingly. When tested in Watts bath for nickel plating, the proposed design successfully recorded the evolution of internal stress with respect to plating thickness. Comparing with the results from commercial bent strip method and the literature, the proposed design was capable of measuring both tensile and compressive internal stresses during electroplating with good precision.