Vishay - FRSH Wraparound Chip Resistors for High Temperatures to +225°C Featuring Exceptional Load-Life Stability to ±0.05% at +200°C for 2,000 Hours at Working Power

31st August 2011
ES Admin
Vishay has announced that its Vishay Foil Resistors division has released a new series of ultra-high-precision Bulk Metal® Z1-Foil wraparound, surface-mount chip resistors with extended pads for high-temperature, high-power applications. The new extended pad designs are optimized for applications at temperatures as high as +225°C, and they offer improved heat dissipation for high working power to 1,200 mW at +70°C and 330 mW at +200°C.
The FRSH series is based on VFR's next-generation Z1-Foil technology, which provides an order of magnitude reduction in the Bulk Metal Foil element's sensitivity to temperature compared with the classical Foil — both external and internal — while providing long-term stability in high-temperature environments. FRSH devices offer TCR of ±1 ppm/°C from -55°C to +125°C and ±2.5 ppm/°C from -55°C to +200°C, +25°C ref. The resistors feature exceptional load-life stability to ±0.05% at +200°C for 2,000 hours at working power, long-term stability to ±0.05% at +225°C for 2,000 hours, and tight tolerances to ±0.02%. The devices' full wraparound terminations ensure safe handling during the manufacturing process and provide stability during multiple thermal cycling. The devices are also capable of withstanding electrostatic discharges at least to 25 kV without degradation.

Offered in six chip sizes from 0603 to 2512, the FRSH series features a wide resistance range from 10 Ω to 125 kΩ, with any resistance value within this range available at any tolerance with no additional cost or lead-time effect. 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 0.01 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 TCR of the FRSH resistor is achieved through a relatively thick cold-rolled foil that maintains the same molecular structure as the raw alloy in high-temperature conditions. This represents the basis of the foil resistor because the foil must act as a monolithic structure with a fixed and known linear coefficient of expansion over any temperature range the resistor might experience throughout its design life. The next most important element in the resistor's construction is the adhesive that holds the foil to a flat substrate. It must withstand high- and low-temperature exposure, pulsing power, moisture incursions, shock and vibration, and more while still securely holding the foil element to the substrate. With these characteristics, the basic technology of foil resistors combines the essential stress compensation that defines the foil technology.

There has been considerable growth in the demand for precise, stable, and reliable resistors that can operate in harsh environments and especially at high temperatures above +200°C and +220°C, said Yuval Hernik, senior director of application engineering for Vishay Foil Resistors. Many analog circuits in these applications require passive components such as resistors to have a minimal drift from their initial values when operating above +175°C and in humid environments. But the most important factors are the end-of-life tolerance and, to a lesser extent, the initial tolerance. The new Vishay Foil resistors provide stabilities well under the maximum allowable drift required by customers' specifications through thousands of hours of operation under harsh conditions.

The FRSH series is optimized for a wide variety of demanding high-power, high-temperature applications including power supplies, geothermal measuring equipment, turbine engine control, and environmental test chambers in military, industrial, automotive, and down-hole drilling systems. 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 environment 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.
Samples and production quantities of the FRSH series are available now, with lead times of five days for samples and six weeks for standard orders.

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