VPG releases FRST wraparound chip resistors for high-temperature applications

The Vishay Precision Group’s Vishay Foil Resistors brand (VFR) has released a new series of ultra-high-precision Bulk Metal Z1-Foil wraparound, surface-mount chip resistors for high-temperature applications up to +200°C. The FRST devices provide a high-temperature load-life stability of 0.02% ?R after 2,000 hours of rated power at 175°C, 0.015% typical ?R after 1,000 hours at 85°C/85% relative humidity, and low TCR of ± 2.5 ppm/°C from -55°C to +175°C, 25°C ref. Rated power varies depending upon the chip size.

VFR”s Bulk Metal Foil technology”s principal advantage has been its insensitivity to temperature changes, a benefit that’s been enhanced in VFR”s next-generation Z1-Foil technology. The FRST series incorporates Z1-Foil technology to extend these critical performance features to higher-temperature and higher-humidity environments while maintaining the same low TCR. Each device”s solid monolithic alloy element is matched to the substrate, forming a single interdependent structure with balanced temperature characteristics for an unusually low and predictable TCR over a wide range from -55°C to more than +175°C. Resistance patterns are photo-etched to permit trimming of resistance values to very tight tolerances of ±0.01%.

The resistors feature load-life stability to ±0.0025% at +70°C for 2,000 hours at rated power and can withstand electrostatic discharges at least to 25 kV without degradation. Offered in six chip sizes from 0603 to 2512, the FRST series features a wide resistance range from 5

O to 125 kO, with any resistance value within this range available at any tolerance with no additional cost or lead time effect.

FRST devices offer a power coefficient (?R due to self-heating) down to 5 ppm at rated power within ±25°C of room temperature, and power ratings for the devices range from 750 mW at +70°C to 150 mW at +175°C. The resistors feature a rise time of 1.0 ns with effectively no ringing, a thermal stabilization time of <1 s (nominal value achieved within 10 ppm of steady state value), current noise of 0.010 µVrms per volt of applied voltage (<-40 dB), and a voltage coefficient of <0.1 ppm/V. The RoHS-compliant devices offer a non-inductive (<0.08 µH), non-capacitive design and are available in matched sets upon request.

The FRST series is optimised for a wide variety of industrial, military, aerospace, medical, down-hole, oil well, and automotive applications requiring resistors to have a minimal drift from their initial values when operating above +175°C and in humid environments. The Z1-Foil technology allows VFR to produce customer-oriented products designed to satisfy unique and specific technical requirements. In addition to the special chip stabilization under extreme environmental conditions in the production line, additional specially oriented postmanufacturing operations (PMO) are offered for high-temperature applications that require an even higher degree of reliability and stability.

“Z-1 Foil technology in general — and the FRST in particular — is another step in tailoring previously unavailable high-reliability, high-temperature resistors to the high-temperature and high-humidity markets. The new FRST resistors provide stabilities well under the maximum allowable drift required by customers” specifications through thousands of hours of operation under harsh conditions, such as the extreme temperatures and radiation-rich environments of down-hole oil-well logging applications, in the frigid arctic, under the sea, in deep space, and especially humidity conditions of 85°C/85% relative humidity,” said Yuval Hernik, senior director of application engineering for Vishay Foil Resistors.

“All Bulk Metal Foil resistors receive stabilization processing, such as repetitive short-term power overloads, to assure reliable service through the unpredictable stresses of extreme operation. Compared to Bulk Metal Foil, thick and thin film resistor elements are produced with marginally controllable resistance materials. Heat or mechanical stresses on the resistive elements cause the particles forming the film to expand. After these stresses are alleviated, the particles in the film matrix do not return to the exact original position. This degenerates their overall stability.”

Samples and production quantities of the FRST series are available now.



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