A Steady State, Thermal Model of an On-Chip Assembly of RTD Heaters, Sputtered Sample and Microthermocouples

Abstract

An experimentally validated one-dimensional (1D) steady state, analytical model has been presented in this paper for the in-plane thermal field of an on-chip assembly of a Resistance Temperature Detector (RTD), a sputtered thin film and microthermocouples (MT). The model is used to suggest a threshold condition for the design of an MT that may result in an overheating of the two cold junctions of the MT beyond the ambient temperature, as well as asymmetry between the two cold junction temperatures. A second threshold condition is suggested for the range of normalized thermal conductivities of the sputtered thin film that will have an impact on the thermal field. Such a model may be useful for preliminary design of structures to determine in-plane thermal conductivities of isotropic sputtered thin films.

Saline soak tests to determine the short-term reliability of an in situ thin film resistance temperature detector

“…While RTDs have typically been used to estimate temperatures based on the temperature-dependent electrical resistance of the material, the RTDs in this research have been used as a heat source to create thermal fields in thin films. The open literature has reported work on a wide variety of RTDs, some of which has been fabricated using the following metals: Iron (Fe) and Silicon (Si) alloy [19], Copper (Cu) [20,[22][23][24][25][26]29], and Platinum (Pt) [30][31][32]. The RTD used in this work is made from a Cu thin film, and an optical micrographic image of the fabricated thin film RTD is shown in Fig.…”

“…In reality, the response of an RTD is not only dictated by the material involved, but also its architecture and geometry. We have also studied the effects of film thickness and sputtered material on the thermal response of the RTD [24] as well as the short circuit response of a thermopile [25] by extending an experimentally validated model reported in an earlier publication [22].…”

“…As a result of these experiments, we have developed a detailed steady state analytical thermal model for the in-plane one-dimensional (1D) temperature profile of this assembly [22]. In particular, the response of an RTD was studied with respect to its temperature vs. time and resistance vs. temperature characteristics under free convection conditions, at atmospheric pressure, and for a range of applied voltages while being used as a micro heater [20,22]. In a recently accepted for publication [23], the temperature characteristics of the RTD itself were explored more extensively.…”

“…The RTD and the micro-thermocouples were individually characterized; as part of the process, external thermocouples were used and their contact effects were also quantified [20]. As a result of these experiments, we have developed a detailed steady state analytical thermal model for the in-plane one-dimensional (1D) temperature profile of this assembly [22]. In particular, the response of an RTD was studied with respect to its temperature vs. time and resistance vs. temperature characteristics under free convection conditions, at atmospheric pressure, and for a range of applied voltages while being used as a micro heater [20,22].…”