SUBSURFACE FEATURE LOCATION AND IDENTIFICATION USING INVERSE TLM TECHNIQUES

This paper describes several techniques involving transmission line ma trix modelling which can be used to locate and characterize inhomogene ous features within a circuit package where the thermal response to he ating of the underside is inspected at the top surface. These are used to confirm a semi-empirical thermal non-destructive testing approach to the determination of the lateral dimensions of a feature. The time to maximum contrast is an important parameter which can be used to est imate the depth of the same feature. This paper then describes our app roach to the determination of feature thermal parameters and the influ ence of measurement noise on overall accuracy of the estimate. (C) 199 8 Published by Elsevier Science Ltd. All rights reserved.