Reliability of micro-electronic devices is one of the most important issues in modern technologies and is significantly influenced by the thermal behavior of the components. In this context, we present Liquid Crystal Thermography (LCT) not only as an easy-to-use but even comparably low-cost approach for temperature measurements. This technique is based on thermochromic liquid crystals which exhibit temperature-dependent colors by selectively reflecting incident white light. We describe and demonstrate this method in exemplary investigations of selfheating effects in a half-section ladder-type Surface Acoustic Wave (SAW) filter with silicon dioxide coating. Conventionally, mean temperature values are obtained by evaluating measured frequency shifts under load by means of the Temperature Coefficient of Frequency (TCF). Moreover, LCT provides spatially resolved measurements of the temperature distribution on the component and serves as an independent scheme for thermal characterization in contrast to TCF based evaluations. The results of LCT measurements and temperature simulations are compared and show good agreement.
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. This study presents different schemes for thermal characterization of a half-section ladder-type Surface Acoustic Wave (SAW) filter which is acoustically passivated with a thick SiO2 layer. Unitarity violation quantifies the entire power loss in the device but is unfeasible regarding correlation to each resonator. The Temperature Coefficient of Frequency (TCF) characterizes thermally induced frequency shifts and has the potential to investigate the resonators' temperatures separately in first order. However, uncertainties arise using this indirect approach as soon as other effects causing a frequency shift play a role. Thermographic techniques such as Infrared Thermography (IRT) and Liquid Crystal Thermography (LCT) serve as direct measurement schemes eliminating inaccuracies inherent to TCF based evaluations and show good agreement with simulation results. Moreover, LCT and IRT provide spatially resolved temperature measurements of the component.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.