Thin-film encapsulation (TFE) is of great importance as a barrier film to protect organic devices and displays. A serious problem with the application of TFE is degradation of organic devices with penetration of oxygen and water vapor through pinholes having sub-micron size. Though many studies were tried to identify the pinholes, quantitative analysis of pinhole area has not been found yet. In this study, total pinhole area in TFE layer was quantitatively analyzed with the help of the Cu bumps electrodeposited on the pinholes. Empirical growth rate of the Cu bumps revealed that bump radius (r) and plating time (t) had a relationship of r(3) proportional to t. While size of the pinholes was deduced from starting point of Cu bump growth, number of the pinholes was extracted from size distribution of the Cu bumps. Unique feature of Cu bump morphology is also explained with a compositional analysis, demonstrating dissolution of Ni underlayer and its involvement in the formation of the Cu bumps.