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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.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


    Thank you

    Thank You


    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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