Appliance Design - February 2008 - (Page 37) CONTROLS & SENSORS The AuthenTec fingerprint sensor is a robust component that can provide designers with flexibility regarding its placement on the product. dioxide layer is deposited on top of the wafer to form a protective coating. Typical protective layers generally range from 0.4 microns to 1 micron in thickness. This protective layer allows the fingerprint sensor chips to be assembled into the final package without damage to the delicate circuitry underneath. After traditional packaging, the sensor IC is fully protected by a thick layer of plastic on top of the chip. In the case of fingerprint sensors, the top surface of the package is open to allow physical contact between the finger and the sensing elements. The sensing elements are no longer covered with the package’s protective plastic top, but only with the final protective silicon-dioxide layer. This exposes the sensing array to a host of hazards, many of which can easily damage the sensor. AuthenTec researchers recognized this potential for sensor damage even prior to the company’s formation, and in 1999, worked with fabrication partners to construct a thicker layer measuring 2.2 microns to 2.4 microns. This layer is formed by both the original protective layer of silicon dioxide and by a tough organic material commonly used to product high RPM ball bearings. This dual coating is three to six times thicker than on competing products and significantly more durable. On AuthenTec’s newest fingerprint sensors, including the AES1710 for the wireless market, the organic coating is 5.5 times thicker than competing sensors, and the underlying oxide coating is nearly twice as thick. The improved AuthenTec coating thickness delivers demonstrable durability improvements to impact and scratch resistance, creating fingerprint sensors that are able to withstand more than 10 million rubs. This enhanced level of durability gives OEM product designers the flexibility to mount TruePrint sensors on the outside of www.applianceDESIGN.com the device where A cross section image of the AuthenTec AES1510/AES1610 they can be more sensor taken with a Scanning Electron Microscope (SEM). This product is manufactured using a 0.35 micron triple metal process. easily accessed by The grids shown in the SEM photo represent 1 micron spacing in the end-user. On a both X and Y dimensions. This cross section shows the 2.4 micron phone, for examprotective sandwich coating. ple, the sensor might be placed on On the electrical side of things, integrathe side, back, or open front surface. tion options are numerous. As with any other The user interface is always an important biometric access component, the fingerprint consideration for integrating a fingerprint sensor will require a connection to the host sensor into a product design. For example, the processor, the secured memory, and the first question should be whether the finger or printed circuit board. With embedded applithumb is most likely to be used for authencations, either an SPI or parallel interface will tication on a given device. When examining be required. Software design kits are available these placement issues, product designers to simplify the implementation of biometrics should strive for a design that permits oneinto a device. Such tools have made it easier handed operation, which is usually easier for and faster to integrate biometrics into product the end user. Space above and below the sendesign than in the past. < sor must also be carefully planned to create finger guides that ensure an optimal finger For more information, enter . . . . . . . . . . . . . . . . . . . . . .305 swipe by the user. Or email: info@authentec .com The illustration shows how the TruePrint RF-sensing technology penetrates the outer layer of skin and reads the live conductive layer below, allowing the sensor to read past cuts, scrapes, and oil that might otherwise interfere with accurate sensing. The technology also enables the use of tougher coatings to create more durable devices. applianceDESIGN February 2008 37 http://www.appliancedesign.com
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