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http://www.d-r-t.com/sensortech.htm. http://news.thomasnet.com/fullstory/463874. Automotive Sensors: MEMS. Chris Mosser. Outline. Introduce MEMS Applications Automotive Specific Information Fabrication Packaging. http://eed.gsfc.nasa.gov/562/SA_MEMs.htm. http://www.memx.com/.

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chris mosser

http://www.d-r-t.com/sensortech.htm

http://news.thomasnet.com/fullstory/463874

Automotive Sensors: MEMS

Chris Mosser

outline
Outline
  • Introduce MEMS
  • Applications
  • Automotive Specific Information
  • Fabrication
  • Packaging
what are mems

http://eed.gsfc.nasa.gov/562/SA_MEMs.htm

http://www.memx.com/

http://www.memx.com/

http://www.forbes.com/2008/04/22/mems-apple-nintendo_leadership_clayton_in_jw_0421claytonchristensen_inl_slide.html

What are MEMS?
  • Micro(small)
  • Electro(electric components/functionality)
  • Mechanical(mechanical components/functionality)
  • Systems(integrated, system-like functionality)
where do you find mems
Where do you find MEMs?
  • Printers
    • High DPI inkjets
  • Projectors
      • Micro-Mirrors from Texas Instruments
  • Cell Phones
    • Knowles Microphones used in most new cell phones
  • Automobiles
why mems

http://singularityhub.com/wp-content/uploads/2008/08/red-blood-cells.bmphttp://singularityhub.com/wp-content/uploads/2008/08/red-blood-cells.bmp

Red Blood Cells ~ 10um

http://www.vendian.org/envelope/dir2/scaling_construct.html

Human Hair thickness ~ 50um

Why MEMS
  • Small
    • Typically .1-100um feature size
why mems1
Why MEMS
  • Low cost, High yield
    • Use existing IC fabrication technology
    • Made primarily on Silicon Wafers

http://media-2.web.britannica.com/eb-media/22/78522-004-BB539CA9.jpg

why mems2
Why MEMS
  • Favorable scaling for a lot of applications
    • Flow-rate sensors
    • Electrostatics
    • Magnetism
    • Many others
  • Not all applications
    • Solar Power
    • Turbulent Boundary Energy Harvesting
typical applications
Typical Applications
  • Accelerometers
  • Magnetometers
  • Microphones
  • Micro-Fluidics
  • RF-MEMS
  • Bridge to Nanotechnology
automotive mems
Automotive MEMS
  • MEMS Sensors and Actuators used to control various elements of the automobile
    • Powertrain and Chassis control
      • Ex: Manifold Air Temperature
    • Comfort and Convenience
      • Ex: Air-Temperature Control
    • Communications
      • Ex: Wireless
where it began

http://www.quantummatrix.com.my/v1/content/view/231/59/

MAP Sensor

Where it Began
  • 1979 - First recorded use of MEMs in automobiles
  • Federal emission standards required monitoring the air-to-fuel ratio of the engine
    • Density of air value was needed
  • Many different sensor technologies were introduced to solve this problem
  • MAP (manifold absolute pressure) and MAT (manifold air temperature) sensors were developed using MEMS
  • Silicon based MEMS sensors became the device of choice due to low cost and high yield
who developed it
Who Developed It
  • Two groups
    • Delco Electronics Group(General Motors)
      • Used piezoresistive sensing
    • Ford
      • Used capacitive sensing
piezoresistive sensors

Source: IMG(UF)

Diaphragm with two embedded piezoresisters

Piezoresistive Sensors
  • Use the piezoresistive effect
    • Applied stress changes resistivity of material
capacitive sensors
Capacitive Sensors
  • Vary two parameters
    • Gap
    • Overlap area
  • Advantages
    • Low power
    • High accuracy
    • Temperature independent
      • Important for a lot of automobile applications
    • Reciprocal
  • Disadvantages
    • Parasitic capacitance
    • Small signal

http://www.nanoshift.net/Technology.htm

what about actuators
What about Actuators?
  • Traditionally only sensors were developed for automobiles
  • Actuators started to become popular as MEMs development costs decreased
  • Popular actuators include
    • Microphones
    • Fuel injection nozzles
fabrication
Fabrication
  • Use basic IC fabrication
    • Masks/layers/CVD/oxidation/etc
  • MEMS specific fabrication
    • DRIE (Deep reactive ion etch)
    • SOI (silicon on insulator)
general mems packaging
General MEMS Packaging
  • The most important and expensive part of a MEMS sensor/actuator
    • ~45% of the cost of designing a MEMS device is spent on packaging
  • Often times packaging constraints will prevent a design from being produced
    • May require too complex of a package design for realistic implementation
  • Package can greatly change the response of a device
    • Sensitivity/Dynamic Range/etc all effected by package
automotive mems packaging
Automotive MEMS Packaging
  • Automotive sensors generally only allowed to have 3 wires connected to them
    • Minimizes cost
  • Environment concerns are especially important in automotive applications
    • Engine heat
    • High acceleration/deceleration
    • Humidity
automotive mems summary
Automotive MEMS Summary

Precision Engineering

 By V. C. Venkatesh, Sudin Izman

references
References
  • Application of MEMS Technology in Automotive Sensors and Actuators, David Eddy and Douglas Spanks
  • http://www.img.ufl.edu/ms/eel5225/html/assignments.htm
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