The Detection of Ionic Contamination under SM Components

In view of the uncertainty of the applicability of traditional ionic contamination measurement to surface mount assemblies, a mathematical study was made of the phenomena involved. A model was derived, showing that under‐component contamination behaves differently from ordinary surface contamination. By breaking down a curve obtained under practical conditions into its components, it is therefore possible to derive separate figures for surface and under‐component ionic contamination, ignoring the influence of spurious noise signals. A new software, using these techniques, has been written for this application. Comparative tests between non‐destructive testing, using this software, and tests on similar circuits with the components torn off, show that there is a close correlation between the results from these two techniques, even though the under‐component contamination is only partially dissolved with the former method.