New Vishay Foil Resistors Company Demonstration Highlights ESD-Withstanding Capabilities of Bulk Metal Foil Resistors

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 to at least 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.