Packaging of Surface Micromachined Thin Film Thermocouples (TFT): Comparison of the Resistance Arc Microwelding Technique With Wire Bonding

In this paper, we report the packaging of thin film thermocouples (TFT) using resistance arc welding technique. Parallel gap welding and spot welding have been reported in the literature for attaching thin wires to metal thin films. To the knowledge of the authors, this is the first time resistance arc welding has been reported as a packaging technique for microfabricated devices. A brief description of the microfabrication process and chemical analysis using X-ray photoelectron spectroscopy (XPS) of the vapor deposited alloy constituents for the TFT are reported in this study. K-type (chromel and alumel) thermocouple wires were used as targets for physical vapor deposition of the component layers of the TFT. The calibration of the TFT using high-speed data acquisition is reported. The calibration curves of TFT packaged using ultrasonic wire bonding of Al wires are compared with TFT packaged using resistance arc welding of K-type thermocouple wires. TFT packaged using resistance arc welding is found to have better temperature response under steady-state conditions.