Vishay can Deliver Bulk Metal Foil Resistor Prototypes in 5 Working Days

Vishay’s “Panic Button” services relieves circuit designers of the complicated, costly, and wasteful procedure of calculating the value of individual network components, ordering, and then stabilizing, aging, or matching these units to assemble and test their own resistor arrays. Instead, they can supply Vishay with the overall electrical performance specifications, the environmental operating conditions, and the desired physical requirements. Vishay will then select and package the Bulk Metal Foil resistor or resistors in the most suitable combination to meet performance requirements.

Since Vishay’s introduction of Foil resistors in 1962, their inherent properties of high precision and stability have been constantly enhanced in response to ever-tightening customer requirements. To reduce resistance drift, both reversible (due mainly to TCR) and irreversible (due to long-term load and environmental conditions) mechanisms have been investigated and improved. These improvements include the reduction of the non-linearity of the resistance versus temperature curve, and of the difference in response to changing ambient temperature versus changing electrical load.

The result is a low absolute TCR of ± 0.05 ppm/°C from 0 °C to + 60 °C and ± 0.2 ppm/°C from − 55 °C to + 125 °C, + 25 °C Ref., an excellent power coefficient (“ΔR due to self heating”) of ± 5 ppm at rated power, and a load life stability of ± 0.005 % for 2000 hours at + 70 °C.

The devices offer a wide resistance range from 1 mΩ to more than 3 MΩ , and resistance tolerance from ± 0.001 % (10 ppm) when hermetically sealed and ± 0.005 % (50 ppm) when encapsulated. Vishay Foil resistors are not restricted to standard values, and Vishay can supply “as required” values (e.g. 3.123 Ω vs. 3 Ω) at no extra cost or delivery time.

While other resistor technologies can take several seconds or even minutes to achieve a steady-state thermal stabilization, Bulk Metal Foil devices have an almost instantaneous thermal stabilization time of < 1 second, and a nearly immeasurable 1.0-ns rise time, effectively without ringing.

The resistors offer a low voltage coefficient of < 0.1 PPM/V; current noise of < - 40 dB; and thermal EMF of 0.05 µV/°C. The devices feature a non-inductive (< 0.08 µH), non-capacitive design, and offer the utmost in ESD immunity, withstanding electrostatic discharges up to 25 kV, for increased reliability. They are available with lead (Pb)-free or tin/lead terminations.

Vishay Foil resistors can be further enhanced by Post Manufacturing Operations (PMO) exercising after the manufacturing cycle is complete. Some of these exercises are a standard part of the manufacturing cycle and are only repeated during the PMO cycle to gain added stability or confidence in the product. The Foil resistor load-life curve shows an increase in resistance from the first load application, but flattens out to no change after 500 to 1000 hours of loading. This knee in the load-life curve can be removed by a special accelerated load-life operation performed by Vishay, resulting in a flat response immediately after installation. Other resistive devices show a continuous change when subjected to these same stresses and are driven out of tolerance.