P. Kongsubto, S. Kongwudthiti, K. Kamthongsuk, Spansion (Thailand) Ltd., Nonthaburi, Thailand

Summary: Nowadays, the technique for OSP thickness measurement is UV-Spectrophotometer method. Unfortunately, the OSP coating on substrate pad has too small amount to obtain the accurate results from this method so another possible technique will be studied. In this work, we aim to evaluate the possibility of EDS quantitative analysis technique for OSP thickness measurement purpose. The statistical tool was also applied in selecting the setting parameter for EDS analysis and in fitting the curve to initiate the equation for OSP thickness estimation. The obtained EDS analysis data is in terms of %C to % Cu (C/Cu ratio). We success on establishment the relationship between C/Cu ratio and actual OSP thickness as follow: Thickness = -0.024 + 0.34199(C/Cu) – 0.02498(C/Cu)^2. From this equation, once the C/Cu value was obtained by EDS method, then the OSP thickness can be readily calculated.