Development of advanced Cu and Ni temperature sensors on ceramic-coated tubes via electroless plating

Abstract

Considering the high cost of precious elements, it is necessary to replace metals like platinum or gold in the sensor sector. In this work, copper and nickel sensor circuits based on autocatalytic techniques were proposed with the aim of monitoring the temperature of cylindrically shaped (and electrically conductive) components. After electrically insulating the tube, a lithographic masking strategy adapted to the cylindrical surface was employed. The surface was functionalized with silanes to deposit a catalytic surface composed of palladium and tin. Non-critical materials such as copper and nickel were selected as sensor materials, depositing them over the catalytic surface by electroless plating. These circuits were electrically characterized on a home-designed testing equipment. Electrical resistance was measured over a range of temperatures: from room temperature up to 250 °C. The electrical results for the copper sensing layer evidenced the need for a protective layer. Silicon oxide was chosen as a protective material. However, it was observed that the sensing and protective layers interact due to their chemical affinity. In contrast, the electrical response of the nickel circuit was stable and repeatable after thermal cycling (heating and cooling), indicating that protection was not necessary for the working temperature range. The sensors developed performed well with regards to functionalization of tubes in terms of time response, repeatability, and stability at the maximum operating temperature.