Printed heaters are thin, flexible and shaped to fit car seats, mirrors, medical devices and battery packs. They are made by screen printing conductive inks onto film.
Carbon and graphite inks
Carbon and graphite inks give a defined sheet resistance, measured in ohms per square at a given thickness. Changing the print pattern and layer thickness sets the heater's power at a given voltage.
PTC inks
Positive temperature coefficient (PTC) inks increase resistance sharply as they warm. A PTC heater draws less power as it reaches temperature, so it self-limits without a separate controller and avoids hot spots.
Design points
- Silver bus bars carry current to the carbon or PTC layer
- Cure fully: resistance drifts if solvent remains
- Protect with a dielectric or laminated cover
- Measure resistance after printing, curing and lamination
