The solid state sensor field is making significant technology advances as MEMS permits higher integration and networking improves functionality. These advances are opening up new markets, pushing volumes higher, and increasing the money flowing into continued development.
A key driving factor for sensors is continued development of microelectromechanical systems (MEMS), which rocketed from R&D labs in the 1990s to high volume devices at the dawn of this decade.
As MEMS processing capabilities advance, manufacturers are devising new ways to follow the learning curve that comes with silicon manufacturing. Silicon Microstructures Inc. (SMI) of Milpitas, CA (www.si-micro.com) is pushing forward with piezoelectric sensors that combine the MEMS pressure sensors on a chip with CMOS circuitry including EEPROM. The company has devised techniques that reduce costs and package size over previous architecture that required separate chips for sensing, processing, and signal conditioning.
SMI is now processing CMOS circuits before etching out the micromachined sensing elements, improving yields. Adding EEPROM is a fairly new development, which lets engineers calibrate and re-program devices as parameters change.
As the devices become more sophisticated, there's also a change in the wiring used to link sensors and processors. Networking techniques are being used in automobiles and other fields, opening up new opportunities for sensors. "Today, sensors have three wires—supply, ground, and signal. People are starting to use networking to reduce that to two wires—send and receive," says Dan Dwyer, systems engineer at Concord, NH -based Allegro MicroSystems (www.allegromicro.com).
The automotive industry continues to be a major market for sensors, providing high volumes that help drive down costs. One of the newest applications is tire pressure sensors. Here growth is fueled by a federal mandate that requires 65% of cars sold during model year 2006 to have tire sensing, phasing in after just 10% this year.
In May, Motorola's Sensor Products Division in Phoenix, AZ (www.motorola.com/semiconductors) unveiled internal tire pressure sensor modules, combining a MEMS pressure sensor, microcontroller, RF transmitter, and battery on a module. Motorola's modules are designed to attach to valve stems, though they can also be mounted into wheel wells.
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MEMS meet the road: Tire pressure sensors from Motorola and others are expected to see dramatic growth, buoyed by a government edict.
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The huge boost that comes from government mandates is prompting other sensor makers to pay close attention to Washington. Gregg Stokely, of commercial marketing at BEI Technologies in Santa Barbara, CA (www.bei-tech.com), is closely monitoring a government plan that could mandate the use of electronic stability control systems. These use yaw rate sensors to detect skidding and then work with anti-lock braking systems to straighten the car out.
BEI addresses the high precision part of the market, using micromachined quartz chips. "The piezoelectric qualities of quartz let it produce more signal (higher frequency) per rate of rotation, so quartz has more accuracy," Stokely adds. However, companies, including Motorola, are working on silicon-based accelerometers that monitor three axes using a single chip. Motorola and other companies contend that once those devices become available, the benefits of silicon processing will give them an edge.
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