David Winkler, IRC Product Manager
736 Greenway Road
Boone, NC 28607
Phone: 828-264-8861, Fax: 828-264-8865
Release Date: 04-May-04
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BOONE, N.C. (May 4, 2004) - TT electronics IRC Wirewound and Film Technologies Division is experiencing increased market demand for its precision surface mount current sense resistors, as automakers are adopting the rugged metal element devices for safety circuits in motor control and power regulation applications. The unique design of these low-ohm resistors solves a number of thermal issues common in automotive electronics.

Designated the OARS Series, these resistors feature a resistive element with a unique open air “flow through” design that keeps the resistor’s “hot spot” safely off the PC board and allows air to circulate around it, contributing to cooler operations through increased heat dissipation.

According to David Winkler, product manager at IRC’s Wirewound and Film Technologies Division, the OARS Series resistors are currently being specified by most major auto manufacturers and their Tier One suppliers because they offer a proven solution to specific thermal problems experienced with other types of current-sense resistors.

"As a surface mount device, the OARS Series resistors have compliant terminations that allow them to expand and contract with the PC board's thermal cycling, enabling them to meet or exceed the 1,000 - 2,000 cycles required by most of the automakers. This thermal cycling stresses the solder joints of conventional flat chip resistors, which can often cause failures; while the unique lead form of the OARS resistors provide an inherent advantage in compliance to the mechanical stress caused by thermal cycling. The welded copper terminals in the OARS Series also provide a low-resistance terminal to enhance reliable performance for demanding applications."

Winkler added that the OARS devices are extremely rugged, with the ability to handle surge currents far higher than conventional resistors. "We've surge-tested these parts up to 100 amps for 1 second, with minimal or no change in resistance value. And because there are no organic materials used in their construction, the OARS resistors are inherently flameproof - an important consideration in many automotive applications."

Although the OARS Series resistors are rated for 1W at 85ºC, Winkler reports that many automotive customers have successfully increased the device's heat dissipation to as high as 4 watts by employing high temperature solder, ceramic or metal substrates or extra copper on the PC board landing pads.

Automotive applications for the OARS Series resistors include ABS systems, window lift and sunroof motors, wiper controls, body computers, power steering systems, seat belt pre-tensioners, fuel pumps, heated seats, flasher modules and solenoid controls. The resistors are typically used in current sense, feedback and surge protection circuits.

The OARS Series resistors are rated for 1W at 85ºC (2W at 25ºC) and 50V continuous with resistance values from 0.002ohm to 0.05ohm, with tolerances down to ±1%. They feature TCRs as low as +20ppm/ºC and inductance values in the single-digit nanoHenry range. Operating temperature range is –40ºC to +125ºC. IRC will also produce OARS Series resistors to customer requirements outside these standard specifications.

The resistors are designed to fit a standard EIA 2512 solder pad, measuring just 0.440 inches x 0.125 inches with a board-mounted profile of 0.120 inches. They are available in tape and reel packaging and are compatible with high-speed automated assembly equipment.

Typical pricing for OARS Series resistor ranges from $0.19 to $0.23 based on automotive industry volumes. Lead-times are from stock to 8 weeks.

For additional information about the IRC Wirewound and Film Technologies Division contact them at 828-264-8861, via mail at P.O. Box 1860 Boone, N.C. 28607, e-mail at waftsales@irctt.com, or visit IRC on the web at www.irctt.com.

IRC Inc. is a leading international manufacturer of advanced film, metal glaze and wirewound resistive products with facilities in Boone, N.C.; Smithfield, N.C.; Barbados, West Indies; and Corpus Christi, Texas. IRC is part of TT electronics plc, a leading global electronics company manufacturing a range of specialist products, including electronic passive components, electromechanical and electronic assemblies and sensor modules for the automotive, telecommunications, computer, medical and aerospace markets. TT electronics' Web site can be found at: www.ttelectronics.com.

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Keywords: TT electronics, IRC, OARS, resistor, automotive, current-sense

URL: http://www.irctt.com/pdf_files/OARS.pdf