Reliable miniaturized wireless sensors for automotive applications

Moore's Law predicts the shrinking of integrated circuits. Today's rapid development in packaging technologies allows additional downscaling of self-sufficient wireless sensors from some cubic centimetre to less than 1cm3. Ongoing system miniaturization at the Fraunhofer Institute for Reliability and Microintegration (IZM) targets an edge length of 6 mm. These wireless sensors reduce the wiring complexity and mounting costs in the automotive industry while substituting signal wires by radio communication. They allow efficient solutions for applications like tire pressure monitoring systems, which requires low weighted self-sufficient sensors to reduce out-of-balance forces. Furthermore the lowering of substrate area reduces mechanical stress applied to the electronic device. Tiny wireless ultrasonic sensors and cameras mounted on external rear mirrors are further instances to monitor blind angles and to be integrated into parking distance control systems. Innovative packaging technologies and power aware design enable system shrinking considering automotive requirements. During the design process the coupling of very narrow positioned components have to be addressed. The counter measures can be selected either by software, hardware or technology. The methodologies of an ultra low power design are fundamental during the development of tiny wireless sensors to allow ultra dense system integration with innovative packaging technologies for automotive applications. Thereby exploitation of battery effects increases operation time. The relevant miniaturisation aspects are discussed on the exemplary application of a tire pressure monitoring system currently reaching 10 g in weight and five years of operation period.