A Printed Circuit Board assembly (PCBA) testing approach using infrared thermal signatures is presented. The concept of thermal signature for PCBAs is introduced. Based on this concept, the testing method is able to: - detect assembly defects such as presence, polarity, value and solder (shorts and opens) and in some cases component health state - classify the components mounted on the PCB into a number of classes (e.g. – fault free(reliable), functional (less reliable), faulty ). According to the thermal signature of each component on the PCBA, PCBAs can be also classified in the same number of classes. In this article a special focus is put on capacitor defects especially capacitor value defects. Therefore, they will be the main components tested. The fault detection indicator used in this proof of concept is a statistical mean squared error measure (MSE).