Active Thermography Diagnostics of Hidden Defects in Multilayer FR-4 Substrates

This paper discusses the applicability of pulsed and lock-in thermography using Fourier transform processing to diagnose specific types of defects in Multilayer FR-4 Substrates. Digital thermal models of test specimens with different types of defects have been created. Based on the obtained results, the methods are compared in terms of applicability and reliability in defect detection. The results show that by these methods can be detected and characterized in terms of geometric dimensions and type of certain types of specific defects arising in the production of FR-4 multilayer substrates. The presented results show that there is no obstacle to the detection of defects in different layers of the multilayer substrate within the same measurement, as well as the possibility of detecting many types of defects.