Electronics interconnections for extreme space environments

If all goes as planned, two rovers named Spirit and Opportunity will explore the surface of Mars next year, gathering a wealth of geologic information and beaming the results back to Earth. However, the environment is so extreme that the rovers will be equipped with heaters to keep the electronic gear warm enough to operate properly over the Martian winter when temperatures can dip to -120 degrees C. Future space probes will involve even more extreme environments, with temperatures as high as 460 degrees Celsius (860 degrees Fahrenheit) on Venus and as low as -180 Celsius (-292 Fahrenheit) on Titan, the largest moon of Saturn.

George Harman, a world authority on materials for microelectronic interconnections and packaging at the National Institute of Standards and Technology (NIST), recently made a workshop presentation for National Aeronautics and Space Administration (NASA) engineers at the Jet Propulsion Laboratory on designing semiconductor device interconnections to withstand extreme space environments.

Harman recommended that spacebound microelectronics interconnections be made with corrosion resis-tant, highly stable metals, especially gold. He also suggested the use of some newer polymers that can withstand extreme temperatures but are not yet used in the space program. “Flip chips” are another interconnection approach, that, with proper metallurgy, may make sense in high-temperature planetary environments. Instead of using wire leads around the edges of a microchip to export electrical signals, flip chips normally use a pattern of ball-shaped solder contacts that are attached directly on the chip surface. Harman suggested that NASA consider using flip chips designed with gold contacts to produce spacecraft electronics that are both space-saving and heat resistant.