Sensitivity of a stress measurement method for copper electroplating using the effects of stress concentration

This study deals with the sensitivity of a copper electroplating method to measure stress by taking the effect of stress concentration into account. The electroplating method of strain analysis is based on the colour changes on the surface of electroplated copper resulting from cyclic stress. This has proved to be of use in determining accurately the peak stress in notches and in measuring the microscopic strain distribution in metals. However, there is a limitation on the measurement of stress using copper electroplating; low level stress, below 130 MPa, cannot be measured. The effect of stress concentration brought about by the control of fine slits was used in copper foil electroplating in order to increase the sensitivity. The results showed that the sensitivity was improved significantly, by more than 50%, proving that this method is reliable. Copper electroplating foil gauges with a 0.6.m slit width and a 45° slit angle can measure stress down to 44 MPa.