Evaluation of element/electrode joining by thermographic NDT method

Joining of semiconductor element and metal electrode is very important part in thermoelectric module; since both electrical and thermal current pass through them, such defects as flaws and pores lurking in element/electrode joining has serious effect on performance of the thermoelectric module. Then we have developed a nondestructive testing (NDT) method to evaluate the element/electrode joining. A current was applied to conventional-type thermoelectric module and temperature change of the defects has been observed on the substrates; not only the Joule heating but the Peltier heating/cooling by electrical current has been thought to play an important role of this method. With this method, one can get the size of defects as well as the location of them, which was unable to detect by conventional electrical resistance measurement. Therefore, this technique is applicable to developing the element/electrode joining of the thermoelectric module as well as for the final products testing.