Extreme-Environment Electronics for the Future
Electronics have dramatically changed the way we live, conduct business, communicate, and educate. Visions of the future foretell of ubiquitous computing and sensing. However, the environments in which electronics can reliably operate are limited. In consumer applications, typical operating temperatures range from -40° to 85°C. The “wider” military temperature range is only -55° to 125°C. Electronics are susceptible to radiation exposure not just in space applications, but also here on Earth. This is because the continued scaling of device dimensions has made the effects of residual radiation a critical reliability issue for manufacturers of consumer electronics. Single-event effects (SEE) caused by cosmic rays, for example, can produce either hard or soft errors. These errors have been observed both on the Earth’s surface at levels that can measurably affect commercial microelectronics, and in avionics at levels that can jeopardize the reliability of these systems if mitigation strategies are not used. The use of electronics in corrosive chemical or high vibration environments also places severe constraints on system complexity and reduces overall reliability.
Energy. Petroleum will still be the dominant source of energy 20 years from now, according to Department of Energy projections, despite advances in alternate energy sources. To increase oil and gas discovery and recovery, instrumentation is required that can withstand well temperatures varying from 150° to more than 300°C and pressures that can reach 25,000 psi. These wells also contain steam, corrosive gases, and naturally occurring radiation. During drilling, the drill and associated logging instrumentation are subjected to high levels of shock and vibration.
Transportation. Transportation is an important manufacturing segment in the world economy and a critical infrastructure for moving goods, services, and people. In the automotive industry, the system design trends are toward mechatronics (integration of electronics and mechanical systems) and X-by-wire (X = throttle, steer, shift, and brake). The goals are distributed electronic architectures, replacing mechanical and hydraulic systems with electromechanical systems to simplify assembly, improve fuel efficiency, and increase safety.
Hybrid electric and future fuel cell vehicles will further increase the electronics content. The power and control electronics for these vehicles will require either elaborate cooling systems or electronics capable of reliable operation at high temperatures (Table 1). In addition to temperature, automotive electronics are exposed to extreme conditions such as wide thermal cycles, shock, vibration, fluids, and corrosive gases. Many next-generation mechatronics systems will use MEMS devices for miniature sensor applications. Packaging of these devices for extreme-environment applications will be critical to the success of these new systems.
Table 1. Automotive maximum ambient temperatures.
High-temperature, radiation-tolerant electronics are needed by the commercial aircraft industry. Hydraulic systems of today will be replaced by distributed electromechanical systems to improve performance and decrease maintenance costs, weight, and fuel consumption. These distributed electronics and sensors will be located in high-temperature locations, including on-engine where temperatures can reach 500°C.
Space Exploration. Distributed electronics able to operate in the ambient lunar and Martian environments are necessary to enable the lunar/Martian vision of habitats, rovers, mining and manufacturing, orbiting vehicles, etc. In the equatorial region of the moon, the temperature cycles between -180° and 120°C, while in the polar shadows and in shadowed craters, the temperature is -230°C. Electronics will be increasingly susceptible to single-event affects due to cosmic rays and high-energy particles associated with solar activity. On Mars, the temperature cycles from -120° to 85°C, with increased radiation levels.
Small-scale Mars rovers, such as Spirit and Discovery, use warm electronics boxes to maintain an earth-like temperature. This results in more than 2,000 point-to-point wires, increasing system complexity and weight. This centralized approach will be limiting as larger vehicles are needed. For intelligent, distributed sensors and actuators, electronics and sensors must operate in the ambient temperature.
These and other applications for extreme environment electronics provide exciting challenges for design, device, and packaging technologies.
R. WAYNE JOHNSON, Ph.D., professor, may be contacted at Auburn University, 162 Broun Hall/ECE Dept., Auburn, AL 36849; (334) 844-1880; e-mail: email@example.com.