The changing automotive environment: high-temperature electronics

The underhood automotive environment is harsh and current trends in the automotive electronics industry will be pushing the temperature envelope for electronic components. The desire to place engine control units on the engine and transmission control units either on or in the transmission will push the ambient temperature above 125°C. However, extreme cost pressures, increasing reliability demands (10 year/241 350 km) and the cost of field failures (recalls, liability, customer loyalty) will make the shift to higher temperatures occur incrementally. The coolest spots on engine and in the transmission will be used. These large bodies do provide considerable heat sinking to reduce temperature rise due to power dissipation in the control unit. The majority of near term applications will be at 150°C or less and these will be worst case temperatures, not nominal. The transition to X-by-wire technology, replacing mechanical and hydraulic systems with electromechanical systems will require more power electronics. Integration of power transistors and smart power devices into the electromechanical actuator will require power devices to operate at 175°C to 200°C. Hybrid electric vehicles and fuel cell vehicles will also drive the demand for higher temperature power electronics. In the case of hybrid electric and fuel cell vehicles, the high temperature will be due to power dissipation. The alternates to high-temperature devices are thermal management systems which add weight and cost. Finally, the number of sensors in vehicles is increasing as more electrically controlled systems are added. Many of these sensors must work in high-temperature environments. The harshest applications are exhaust gas sensors and cylinder pressure or combustion sensors. High-temperature electronics use in automotive systems will continue to grow, but it will be gradual as cost and reliability issues are addressed. This work examines the motivation for higher temperature operation, the packaging limitations even at 125°C with newer package styles and concludes with a review of challenges at both the semiconductor device and packaging level as temperatures push beyond 125°C.