A Fluorescence Method for Two-Dimensional Quantitative Detection of Organic Residues on Printed Wiring Boards

Organic residues which remain on printed wiring boards (PWBs) even after washing with chlorofluorocarbon substitutes are excited optically and their quantities are estimated with significant accuracy on the basis of their fluorescence. The thickness of residues is related linearly to the intensity of their fluorescence and can be estimated even for very thin layers. The distribution of residues on PWBs is visualized as a two-dimensional map of fluorescence intensity, in which variations in intensity are represented as variations in color. This proposed estimation method is applied here to an examination of the relationship between flux residues and electromigration on PWBs, as well as to an estimation of the effectiveness of washing with trichloroethane substitutes.