Technical Presentation on
Selecting Resistors to Avoid Unforeseen Stress Factors
Dr. Felix Zandman
Founder, Executive Chairman, and Chief Technical Officer, Vishay Intertechnology, Inc.
25 November 2010
Israel Institute of Technology
Electrical Engineering Building Room 1003
14:15 – 15:15 Demo Presentation by Dr. Zandman, Part 1Auditorium 1003
15:15 – 15:30 Coffee Break
15:30 – 16:30 Demo Presentation by Dr. Zandman, Part 2
16:30 – 17:00 Q & A Session
Spoken language: English
Resistors built on different technologies may seem alike on the surface, and may even have similar specifications such as initial TCR and tolerance. But the differences between them remain quite significant. Inherent in each type of resistive material are certain design and processing variations that strongly influence device electrical performance in ways that may become apparent only after a period of use in the end product.
In this tutorial we discuss the primary factors that influence resistor stability in real-world environments and how these can depart from the specifications published in datasheets. Parameters such as temperature (known and unknown), pulse, SNR, CTE (coefficient of thermal expansion) of the PCB, ESD, surface tension, thermal EMF, and more will be covered. We will conclude with a demonstration that illustrates in real time the differences between bulk metal foil, thin film, thick film and wirewound resistor technologies, including their ESD properties.
Bulk Metal® Foil Technology
Bulk Metal® Foil technology, first introduced in 1962, still outperforms all other resistor technologies available for applications that require precision, stability, and reliability. Ultra-precision Bulk Metal Foil resistor products provide extremely low temperature coefficient of resistance, the lowest in industry by an order of magnitude, and exceptional long-term stability through temperature extremes. Features and benefits of Foil resistors include:
• Temperature Coefficient of Resistance (TCR)
• Absolute TCR: ±0.05 ppm/?C (0 ?C to +60?C) typical; 0.2 ppm/?C (–55?C to 125?C with 25?C reference)
• Tracking TCR: 0.1 ppm/?C typical
• Power Coefficient of Resistance (PCR) “ΔR due to self-heating” — 5 ppm typical at rated power
• Tolerance Absolute: ±0.005%; match: 0.005% (50 ppm)
• Load Life Stability0.005% at 70?C, 2000 hrs at rated power; 0.015% at +125?C, 10,000 hrs at rated power.
• Electrostatic Discharge (ESD) At least to 25 kV
Dr. Felix Zandman
Dr. Felix Zandman was born in Grodno, Poland in 1928. He survived the Holocaust, and went on to become a physicist, inventor, and businessman. Dr. Zandman received a Mechanical Engineering degree from E.N.S.E.M. and Master of Physics degree from the University of Nancy (France), and a Doctorate in Physics from the University of Paris, Sorbonne. Today, he is Executive Chairman, and Chief Technology and Business Development Officer, of Vishay Intertechnology, one of the world’s largest manufacturers of discrete semiconductors and passive electronic components.
Vishay Precision Group
Vishay Precision Group (VPG) produces sensors based on resistive foil technology, and sensor-based systems. VPG provides vertically integrated products and solutions for multiple growing markets in the areas of stress measurement, industrial weighing, and manufacturing process control. As a spin-off from Vishay Intertechnology, the company has a decades-long track record of innovation: in foil precision resistors, which VPG invented, current sensors, and strain gages, which has served as a foundation for more recent expansion into strain gage instrumentation, load cells and transducers, load cell modules, and complete systems for process control and on-board weighing. Vishay Precision Group may be found on the Internet at www.vishaypg.com.