VPG – New wraparound chip resistors satisfy high-temperature applications to 200C (FRST Series)

Vishay Precision Group (VPG) has announced that its Vishay Foil Resistors (VFR) group 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 Series devices provide a high-temperature load-life stability of 0.02% ΔR after 2,000 hours of rated power at 175C, 0.015% typical ΔR after 1,000 hours at 85C/85% relative humidity, and low TCR of ± 2.5ppm/C from -55C to +175C, 25C ref. Rated power varies depending upon the chip size.

VFR’s Bulk Metal Foil technology’s principal advantage has long been its insensitivity to temperature changes, a benefit that has been further improved 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 -55C to more than +175C. Resistance patterns are photo-etched to permit trimming of resistance values to very tight tolerances of ±0.01%.

The resistors feature exceptional load-life stability to ±0.0025% at +70C 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 5ohm to 125kohm, with any resistance value within this range available at any tolerance with no additional cost or lead time effect.

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

The FRST series is optimized 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 +175C 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 post manufacturing 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, 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,” he added.