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Director, Global Marketing Communications,
MALVERN, Pa. — Oct. 12, 2011 — Vishay Precision Group (NYSE: VPG) today unveiled a new video that presents a demonstration of the ESD-withstanding capabilities of two resistor technologies: thin film and Bulk Metal® Foil. Using an ESD testing system and 10 kΩ 1206 resistors, the demo shows that while a single 3,500 V ESD pulse results in a relatively minor 1520 ppm resistance change to a thin film resistor, it also causes several cracks to its resistive element under the external coating. The Bulk Metal Foil resistor, however, experiences no change in resistance or latent defects even after 10 pulses of 3,500 V in rapid succession. Hidden ESD damage results in early-life failures during use and constitutes significant reliability risks in equipment.
Thin film resistors are composed of a metal layer that is only a few hundred angstroms thick. This severely limits the device’s capability to withstand the energy that is passed through it during an electrostatic discharge, causing it to be very sensitive to ESD damage. As a result, thin film resistors have an ESD limit of about 2,500 V and can experience undetectable damage that will affect their long-term stability when that limit is exceeded. ESD pulses of 10,000 V can easily be generated by simply walking across a carpet.
Vishay Foil Resistors’ (VFR) Bulk Metal Foil resistors have a number of characteristics that make them superior to thin film when it comes to withstanding ESD. The resistors are comprised of a single layer of special metal alloy rolled into a Foil and mounted on a highly thermal-conductive ceramic substrate. In addition, the Foil is typically 100 to 200 times thicker than its thin film equivalent, and thus provides a much higher heat capacity in the Foil resistor. The result is a resistor capable of withstanding ESD at least to 25 kV without any degradation.
Even with the best safeguards, ESD damage to electronic devices can occur at any point in the device’s life cycle, from installation during manufacturing to field service. A resistor that is exposed to an ESD event may fail immediately or may experience a latent defect, which is damage to the device that is not readily noticeable because the resistor appears to be functioning correctly. Latent damage is a source for great concern, as it is very difficult to detect by final circuit testing or by visual inspection, since the damage may have occurred under the external coating.
With latent defects, such as the cracking to the thin film device shown in the video demo, premature failure can occur after the resistor is already functioning in the finished product for a period of time, which can be catastrophic in high-reliability applications. If an application is likely to experience ESD pulses of significant magnitude, the best resistor choice for high reliability and stability is the Vishay Foil resistor.
About Vishay Foil Resistors
Vishay Foil Resistors is a division of Vishay Precision Group, producing the most precise and stable type of resistors available. The portfolio comprises products in a variety of resistor configurations and package types to meet the needs of a wide range of applications: discrete resistors and resistor networks in surface mount and through-hole (leaded) 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 and 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 foil precision 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