Fluxless high-vacuum packaging of MEMS and IR sensors

Historically, infrared (M) thermal imaging technology has been driven mainly by military applications. Based upon helium-cooled microbolometers, the cost and size of these systems have limited their-use in many commercial applications such as automotive night-vision enhancement, firefighting, and security systems. Advances in microbolometer technology have brought forth the development of Uncooled Focal Plane Arrays (UFPAs) designed to operate at room temperature, eliminating the need for super-cooling and thereby significantly reducing the cost and complexity of the overall system package. Although uncooled technology will inherently reduce package dimensions, the semiconductor detectors must still be hermetically sealed in a high vacuum environment to maximize the thermal sensitivity of the microbolometer. The timely process of sealing these UFPAs within a high vacuum has traditionally been the largest limiting factor on package throughput. Current technology requires that each pre-assembled package be individually mounted to a high-vacuum pump via a pinch-off tube and. vacuum baked for a number of days before activation of the getters and final pinch-off seal In an effort to meet the demand of increasing volumes, a novel batch-type packaging approach has been proposed which combines a high-vacuum bakeout, activation of getters, and fluxless hermetic package assembly into a single, semi-automated in situ process, significantly reducing the overall cycle time of the sealing process.