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MALVERN, PENNSYLVANIA — Nov. 28, 2011 — Vishay Precision Group, Inc. (NYSE: VPG) today announced that its Vishay Foil Resistors division (VFR) has released a new series of ultra-high-precision Bulk Metal® Foil chip resistors offering flexible terminations, low TCR of ±2.0 ppm/°C typical from –55°C to +125°C, +25°C ref., and load-life stability to ±0.01% at +70°C for 2,000 hours at rated power.
Offered in 1206, 2010, and 2512 chip sizes, the VSMF series features a wide resistance range from 10 Ω to 125 kΩ, with tolerances to ±0.01%. Any resistance value within this range is available at any tolerance with no additional cost or lead time effect. The devices provide a power rating to 400 mW at +70°C and withstand electrostatic discharge (ESD) to at least 25 kV. 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), a voltage coefficient of < 0.1 ppm/V, and a thermal EMF of 0.05 μV/°C. The RoHS-compliant devices offer a non-inductive (< 0.08 μH), non-capacitive design.
Typical chips in sizes of 1206 and larger occasionally fall off the printed circuit board (PCB) or develop substrate cracks, mainly due to bending during assembly and other stresses introduced through handling of the PCB, excess thermal gradients, or thermal shock. Thermal stresses can occur due to changes in ambient temperature or internal heat generation in the resistor itself. Whatever the cause, stress cycling due to thermal phenomena can cause material fatigue and cracks.
The VSMF series eliminates the problems of cracked substrates and board delamination by providing flexible terminations for strain relief, thereby increasing reliability. In addition, the Bulk Metal Foil resistor has documented more precise load-life stability than any MIL-qualified resistor. This is because the resistor’s element is a bulk metal alloy that has been applied to a substrate with a unique process that results in a stress-free adhesion. The adhesion is maintained throughout the manufacturing process, including termination welding, encapsulation, marking, and curing. It then maintains adhesion integrity through all environmental and application stresses.
“Allowances must be made for the stresses – especially mounting and thermal cycling – that will change a resistor’s end-of-life tolerance,” said Yuval Hernik, senior director of application engineering for Vishay Foil Resistors. “These allowances depend on the specific resistor application and the service conditions of the equipment in which it is installed. The less stable a resistor is, the more allowance for instability is required. These allowances are considered cumulative and when subtracted from the end-of-life error budget, impose a tighter tolerance at the point of purchase.”
“Foil resistors with flexible terminations are the most stable resistors, and thus require the least error allowance. The lower in-service error allowance means that more error allowance can be transferred to active devices – resulting in lower costs – or applied to the Foil resistors themselves, allowing for looser initial tolerances than would be required for other resistor technologies.”
Samples and production quantities of the VSMF series are available now, with lead times of five days for samples, and eight weeks for standard orders.
About Vishay Foil Resistors
Vishay Foil Resistors is a division of Vishay Precision Group, producing the most precise and stable resistors available. The portfolio comprises products in a variety of resistor and package configurations to meet the needs of a wide range of applications: discrete resistors and resistor networks in surface mount and through-hole (fixed-lead) configurations; customized chip resistor networks; precision trimming potentiometers; and discrete chips for use in hybrid circuits. The foil resistors and current sensors are used in applications requiring a high degree of precision and stability, such as in medical testing equipment, high performance audio equipment, precision measuring instruments, aerospace, and military applications.
About Vishay Precision Group
Vishay Precision Group (VPG) produces sensors based on precision resistive foil technology, and sensor-based systems. It provides vertically integrated products and solutions for multiple growing markets in the areas of stress, force, weight, pressure and current measurements. As a spin-off from Vishay Intertechnology, VPG’s decades-long track record encompasses innovations in precision foil resistors, current sensors, and strain gages, which have served as a foundation for VPG’s more recent expansion into strain gage instrumentation, load cells and transducers, weighing modules and complete systems for process control and on-board weighing. Vishay Precision Group may be found on the Internet at www.vishaypg.com