Basic requirements in the design and manufacturing of pressure sensors for automotive
applications ensure optimal performance in the range of temperature, vibration,
media, shock, and electromagnetic conditions the sensor must endure to perform vital
functions. Harsh environments require enhanced protection of the sensor's electrical
structures against the pressurized medium. SMI’s pressure sensors are produced using
total quality management in a fab certified to be conformant with ISO/TS 16949 automotive
standards.
Typical requirements for an automotive pressure sensor
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Minimum operating temperature
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–40°C
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Maximum operating temperature
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Passenger compartment
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85°C
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Chassis/wheel
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125°C
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Under the hood
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>140°C
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Static acceleration
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>2000 g (for TPMS applications)
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Dynamic acceleration (shock)
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>5000 g (for TPMS applications)
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Vibration
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20 Hz–2 kHz (over extended time period)
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Chemical resistance
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To all kinds of liquids present in an automobile environment, including the workshop:
fuels, oils, brake fluids, cleaners, waters, salt water
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To this end, the piezoresistive bridge on the micromachined silicon membrane typically
is not exposed directly to the environment in which it operates. Instead, protective
silicone-gel coatings, or caps, form a barrier between the sensor's front side and
harsh environments, such as those involved in MAP and BAP applications (Figure 3).
Field shields and noble metals are also used to protect the sensor's electrical
structures against pressurized media. The idea is to protect the sensor's front
side from the medium and leave only the silicon backside exposed to the harsh environment.
This approach is used widely in tire pressure monitors and MAP sensors.
For more information contact SMI sales at sales@si-micro.com.