2.2.3 Resistors and Heating


Basic requirements for resistors (still one of the most numerous component in circuits) are:
  • Large region of R values (= device resistance in W) within one production technology.
  • Small (ideally vanishing) temperature coefficient .
  • Minimal noise.
  • Small dependence of r on production parameters (good repeatability).
  • No Ageing.
  • Small thermoelectrical coefficients to Cu (you want a resistor, not a thermoelement).
Materials of choice include
Ta, Ta based alloys, and in particular "Constantan" (55% Cu, 44% Ni, 1% Mn), a resistor material with an especially small temperature coefficient ar, but a large thermoelectric coefficient).
Strange mixtures of conductors and insulators including "Cermet" (short for Ceramics - Metals), e.g. Cr - SiO2.
Details and data in the (future) link.


Basic requirements for heating elements are:
  • High melting point.
  • Chemical stability at high temperatures and in potentially corrosive environments.
  • Mechanical strength at high temperatures.
The choice of a materials depends significantly on the range of temperatures envisioned. We have:
FeNiCr, FeNiAl alloys.
Pt, W, Ta, Mo - stable elements with a high melting point.
MoSi2 Among more industrial applications also used as heaters in dish washers - this is very aggressive environment!
Graphite (up to 3000 K in non-oxidizing gas).
Some details and data can be found in the links.
Overview of resistivity and temperature range for some materials
Maximum temperatures for some materials

With frame Back Forward as PDF

© H. Föll (Electronic Materials - Script)