IRC current-sense resistors deliver high thermal performance

irc-oars-3seriesBoone, N.C. — TT electronics IRC offers a series of open-air current sense resistors, aimed at power electronics design engineers looking for high-current devices capable of providing current-sense and surge protection functions in high-temperature environments.

The OARS-3 Series of surface-mount metal alloy strip resistors feature a flameproof open-air design that elevates the device’s “hot spot” above the printed-circuit-board (PCB), where heat can be dissipated to ambient air instead of to adjacent thermally-sensitive components, says IRC. This unique design also gives the resistors superior thermal temperature cycling performance, according to the passives manufacturer.

“The OARS-3 Series resistors feature a heavy-gauge alloy resistive element with welded copper terminations,” said Bryan Yarborough, application engineer for IRC, in a statement. “Combined with its unique curved shape, these features give the resistor flexibility to virtually eliminate the shearing force to the solder joint caused by the differences in thermal expansion between the PC board and the device. Unlike flat chips, these open-air resistors minimize the stress on their solder connections to the PC board, resulting in significantly better long-term solder joint reliability.”

The resistors’ ability to operate reliably under elevated temperature conditions makes them suitable for computer power supplies, high-reliability server equipment, and automotive under-the-hood applications.

The OARS-3 Series resistor performs at 3 watts; however, testing conducted by IRC engineers demonstrate that the resistor is capable of handling higher power levels without forced air depending on system thermal design. The devices provide a 3-watt rating in the same industry-standard 2512 package as a 1-watt flat chip resistor.

Testing at 4 watts reveals that, although the “hot spot” temperature can reach in excess of 230°C when the resistor is running at full power, the solder joint remains at 110°C or below.

The OARS-3 Series resistors are nominally rated for 3 W at 70°C, with a resistance range from 2 mohm to 15 mohm and tolerances to +/-1%. Inductance values are less than 10 nanohenries. The operating temperature range is -40°C to +125°C. RoHS-compliant and zero-ohm jumper versions are also available. Custom specifications are available.

Availability: Lead time is from stock to 14 weeks.
Pricing: Approximately $0.86 each in minimum order quantities of 1900 pieces.