Surface-mount Power Resistor Enhances Thermal Performance

May 18, 2005 12:53 PM

For design engineers facing thermal cycling issues with power components in high-temperature environments, resistor manufacturer IRC has developed a “capped” version of its cylindrical power resistor that delivers superior thermal compliance and thermal isolation from circuit boards. Designated the SMC Series, these power Metal Glaze resistors are available in ratings up to 2 W.

According to David Winkler, product manager for IRC’s Wirewound and Film Technologies Division, the SMC Series resistors were designed to solve the problem of thermal mismatch between FR4 PC boards and ceramic components. “Adding a compliant metal cap to the ends of our surface-mount cylindrical power resistors gives them the compliance needed to address thermal management issues that our customers were experiencing with ceramic chip resistors,” he explained. “The capped ends of the SMC Series resistors not only provide a closer thermal match to the PC board, but they also raise the device up slightly to provide better airflow and result in lower overall board temperature.”

Applications for the SMC Series resistors include high power-density applications, such as underhood automotive control units, GFI control circuits, as well as any application where high thermal stress is present, Winkler said. The resistors can be a potential cost saving replacement for bulky surface-mount wirewound devices in certain applications.

The SMC1 Series resistors are rated for 1 W at 70°C, with resistance values from 0.1 Ω to 1 MΩ, in standard tolerances of ±1%, ±2% and ±5%, with TCRs as low as ±25ppm/°C. The SMC2 Series resistors are rated for 2 W at 25°C, with resistance values from 0.2 Ω to 2.2 MΩ, in standard tolerances of ±1%, ±2% and ±5%, with TCRs as low as ±25ppm/°C. Operating temperature range is from -55°C to +150°C. All devices are RoHS compliant and suitable for high-temperature soldering processes. Typical pricing for the SMC Series resistors is $0.15 each in quantities of 5000.

For more information, visit www.irctt.com.

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