Correlation of thickness measurements obtained from cross-sectioning and from X-ray fluorescence spectrometry

Lead finish processes such as hot solder coat and solder plating differ in the deposit thickness distribution across the lead because of the surface thermodynamics of the system. Thickness measurements using the current methods of XRF (X-ray fluorescence) and cross-sectioning were evaluated. Results show that the thickness measurements using XRF correlate well with those obtained using cross-sectioning. However, cross-sectioning is more effective in solder dipped parts because of the nonuniform thickness distribution on the lead where the corner coverage is thinner than that at the center of the lead. XRF measurement of parts processed in solder coat can be influenced by obtaining measurements at the areas of the lead where the deposit is minimum and maximum