Liquid crystal and Infrared Thermography on coated SAW devices

Reliability of micro-electronic devices is one of the most important issues in mobile communication systems and is significantly influenced by the thermal behavior of the components. The present contribution demonstrates Liquid Crystal Thermography (LCT) and Infrared Thermography (IRT) in exemplary investigations of self-heating effects in a half-section ladder-type Surface Acoustic Wave (SAW) filter with thick SiO₂ coating. Conventionally, mean temperature values are obtained indirectly by evaluating measured frequency shifts under load using the Temperature Coefficient of Frequency (TCF). In contrast to TCF based evaluations, LCT and IRT provide spatially resolved measurements of the temperature distribution on the component and serve as an independent and direct scheme for thermal characterizations. The results of LCT and IRT measurements are compared with simulations of the temperature distribution and show good agreement.