This paper presents a method for indicating cracks in die attach materials, which is non-destructive and enables in-situ monitoring of degradation. It is based on the principle that voids or cracks cause the change of thermal behaviour in electronic packages. Therefore the thermal behaviour is due to alter over lifetime. Parametric simulation models have been developed, which enable the prediction of influence of delamination areas on transient thermal properties for different die attach materials in example COB packages. The results show an increase of delamination area, which causes a significant increase of transient thermal resistance. The computational results are validated with experimental measurements, which show a practical feasibility of the proposed method, which can accelerate and simplify lifetime testing of die attach interconnects.