Application note – CO2 laser ablation of copper hairpins for electric motors

BACKGROUND

Electric vehicle motors use U-shaped copper winding elements, commonly referred to as hairpins. These elements consist of rectangular copper wires up to 6mm in width, coated with dielectric enamel or lacquer for electrical isolation. To enable welding and electrical contacting, the ends of these hairpins require removal of the enamel. The table below lists commonly used coating materials. Coating thickness typically ranges between 100μm and 200μm, although busbars may have considerably thicker coatings of plastic, usually polyamide/nylon (PA).

PROCESSING

  • Integration with a galvo scanner facilitates high-speed processing, typically involving multiple laser passes.
  • Hairpins are angled relative to the incident beam, rotating midway through the process or employing multiple lasers to ablate all four sides.
  • Power levels ranging from 100 W to 1kW are applicable. Cycle time varies based on factors such as power, spot size, hatching distance, and pattern.
  • Due to its high reflectivity at the CO2 laser wavelength, copper remains undamaged.
  • Results vary based on coating composition, with PI presenting the most challenges. This results in a charred residue.
  • The process often leaves a thin residual layer, which cannot be removed by the CO2 laser alone. Additional processing is necessary, typically utilizing a YAG or fiber laser. PA coatings typically leave no residue and are solely ablated using a CO2 laser.

APPLICATIONS LAB

Our applications lab features galvo systems operating at 120W and 450W power levels. If you wish to have samples tested or need more information about this application, please reach out to sales.support@luxinar.com.

Ablation of polyimide coating results in the presence of charred residue.


Most coatings can undergo ablation without producing charred residue.

Coating type Processing
Polyether ether ketone PEEK CO2 + YAG/fibre
Polyimide PI CO2 + YAG/fibre
Polyamide-imide PAI CO2 + YAG/fibre
Polyethersulfone PES CO2 + YAG/fibre
Perfluoroalkoxy
(Teflon™)
PFA CO2 + YAG/fibre
Polyamide (nylon) PA CO2 only