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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. 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

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  1. http://www.d-r-t.com/sensortech.htm http://news.thomasnet.com/fullstory/463874 Automotive Sensors: MEMS Chris Mosser

  2. Outline • Introduce MEMS • Applications • Automotive Specific Information • Fabrication • Packaging

  3. 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)

  4. 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

  5. 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

  6. 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

  7. 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

  8. Typical Applications • Accelerometers • Magnetometers • Microphones • Micro-Fluidics • RF-MEMS • Bridge to Nanotechnology

  9. 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

  10. 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

  11. Who Developed It • Two groups • Delco Electronics Group(General Motors) • Used piezoresistive sensing • Ford • Used capacitive sensing

  12. Source: IMG(UF) Diaphragm with two embedded piezoresisters Piezoresistive Sensors • Use the piezoresistive effect • Applied stress changes resistivity of material

  13. 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

  14. 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

  15. Fabrication • Use basic IC fabrication • Masks/layers/CVD/oxidation/etc • MEMS specific fabrication • DRIE (Deep reactive ion etch) • SOI (silicon on insulator)

  16. 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

  17. 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

  18. Automotive MEMS Summary Precision Engineering  By V. C. Venkatesh, Sudin Izman

  19. Thank You

  20. 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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