Characterisation of die attach for power devices using thermal impedance measurement - practice and experiment

This paper describes a technique for measuring cooling curves at power levels of up to 65W. The paper describes in detail a suitable constant temperature fixture to keep a test vehicle at a constant temperature for these power levels. In this experiment a power diode in bare die form is used as the heating source. The diode V_f is used for junction temperature sensing. The cooling curve method of temperature characterisation is used at this power method of temperature characterisation is used measure when special designed thermal test chips are not available. A special test vehicle was designed to obtain equal temperature distribution across the test diode. The test vehicle has a three layer structure to minimise the number of thermal layers. This enables a more precise cooling curve analysis later in this project. The experimental is part of a project, the objective of which is CFD models. From these CFD models, the thermal resistance and thermal capacitance of the die attach layer can be evaluated. This experiment is part of a project, the objective of which is to thermally characterise die-attach materials for power applications.