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Film Resistors: Coated Core and a Cut Helix
Most axial-leaded resistors are film resistors. A thin resistive film is put on an insulating core, and a helix is cut through it, turning the film into a long, narrow path; the length of that path sets the resistance. Carbon film resistors use a film of carbon and cover about 1 ohm to 10 megohms at 0.125–5 W. Metal film resistors are usually coated with nickel chromium, applied for example by sputtering in a vacuum; cut the same way, they reach tolerances of 0.5–2 % and temperature coefficients of about 50–100 ppm/K. The value is marked on the body with coloured bands, the electronic colour code.
Advanced
Factory process
Instructions
1
1
Coat the cores
Coat the cores
Deposit the resistive film on the insulating cores: carbon for carbon-film parts, nickel chromium (for example by sputtering) for metal-film parts.
Materials for this step:
Insulating Resistor Core1 as required
Carbon Film Coating1 as required
Nickel-Chromium Film Coating1 as requiredTools needed:
Vacuum Sputtering Chamber2
2
Cut the helix and fit leads
Cut the helix and fit leads
Cut a helix through the film (the longer and narrower the path, the higher the resistance) and fit end caps with axial leads.
Materials for this step:
Resistor End Caps with Leads1 as requiredTools needed:
Resistor Helix-Cutting Machine3
3
Mark
Mark
Paint the colour bands that give the value and tolerance.
Materials for this step:
Colour-Band Marking Paint1 as requiredMaterials
5- 1 as requiredPlaceholder
- 1 as requiredPlaceholder
- 1 as requiredPlaceholder
- 1 as requiredPlaceholder
- 1 as requiredPlaceholder
Tools Required
2- Placeholder
- Placeholder
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