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Cylindrical resistors approach wirewound performance

Posted: 06 Oct 2006 ?? ?Print Version ?Bookmark and Share

Keywords:TT electronics? IRC? HSF? SMC? cylindrical resistors?

IRC's HSF and SMC series cylindrical resistors

TT electronics IRC Wire and Film Technologies Division offers two versions of its cylindrical surface-mount resistors aimed at surge/pulse applications and circuits subject to extreme thermal cycling. The HSF series (for surge/pulse applications) and SMC series (for high thermal cycling circuits) are said to approach wirewound performance while providing a cost savings.

Thick-film resistive element
Both devices use IRC's MetalGlaze thick-film resistive elements on cylindrical ceramic substrates, which are said to provide better heat dissipation, improved solderability and improved surge/pulse capabilities.

The HSF series features an unspiralled thick-film element that offers three times the surge rating of IRC's standard CHP series, or as much as 10 times the rating of a conventional flat chip 2512 component. Designed to fit within the footprint of a standard 2512 chip, the HSF Series saves a significant amount of board space versus a comparable rated wirewound device.

The HSF series resistors feature a power rating of 1W at 70C and a working voltage of 350V. The series is offered in the following resistance values: 5.9 ohms, 11 ohms, 27 ohms, 68 ohms, and 270 ohms, with a tolerance of 10 percent, and temperature coefficient of resistance (TCR) to 50ppm/C. The maximum operating temperature is 150C. Custom resistance values are available.

Maximum thermal compliance
The SMC series resistors are designed to provide maximum thermal compliance for use in applications that are subject to extreme temperature cycling. Metal caps fitted on the terminals of the cylindrical resistor body are said to provide the SMC devices with exceptional thermal compliance, relieving stresses created from the thermal coefficient of expansion (TCE) mismatch between the ceramic component and the FR4 circuit board. Designed to fit within industry standard 2512 and 3610 footprints, the SMC series devices are suitable for automotive, power supply and industrial applications that require a surface-mount resistor with excellent surge and thermal characteristics.

The SMC series resistors have a maximum power rating of 1W at 70C for the 2512 package and 2W at 70C for the 3610 size. The devices are available with resistance values of 1 ohm to 2 megaohms, with standard tolerance to 5 percent, and TCRs to 50ppm/C. The maximum operating temperature is 150C. Custom specifications are available.

Typical pricing for the HSF and SMC series resistors is approximately 18 cents each in quantities of 10,000. Delivery is from stock to four to six weeks.

- Gina Roos

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