Burn-in and thermal cyclic tests to determine the short-term reliability of a thin film resistance temperature detector

In this paper, experimental data and theory are presented for two methods of the thermal failure of a multi-layer, thin film resistance temperature detector (RTD). The methods are: (i) while placed in a low pressure inert gas atmosphere, the temperature of the RTD was increased incrementally by means of joule heating until failure (burn-in test), and (ii) the RTD was thermally cycled in both a low-pressure inert gas atmosphere as well as in air at atmospheric pressure. The performance of the RTD was analyzed with respect to three factors: (i) changes in electrical resistivity with respect to temperature of the Ti–Cu–Ti trace that forms the conductive path of the RTD, (ii) degradation of the encapsulation layers, especially the Benzocyclobutene (BCB) with emphasis on its impact on radiation, and (iii) failure of the trace due to crack formation. Environmental effects on performance and probable causes of failure are discussed.