PTC temperature sensors on curved LTCC–layers

To carry out studies on the warming-up of wind instruments, temperature sensors are required that exactly fit into the tube of the instrument. A PTC (positive temperature coefficient) temperature sensor was developed in LTCC (low temperature co-fired ceramics) technology, solving this problem. To keep the overall design small, a very simple geometry was used that just consists of one ceramic tape layer with PTC resistor and 4-wire connection pads on top. The PTC sensor was laminated around a rod and sintered inside a pipe to achieve the desired curvature. Various different ceramic tape materials were used and the electrical properties of the PTC sensor were measured with respect to varying curvature (flat, diameter 12 mm and 18 mm) where resistor elements were positioned in both axial and radial orientation. Finally, the results were obtained by usage of CeramTec GC tape, ESL PTC26xx-I PTC-paste and ESL 9695-G conductor paste. The curvature showed no influence on the TCR (resistive temperature coefficient). The resistance of the curved resistors in axial as well as radial orientation was lower compared to the flat structure.