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

BACKGROUND

Electric vehicle motors utilise U-shaped copper winding elements commonly known as hairpins. These are formed from rectangular copper wires up to 6mm in width, coated with dielectric enamel or lacquer to provide electrical isolation. The enamel must be removed from the ends of these hairpins to allow for welding and electrical contacting. Commonly used coating materials are listed in the table below. Coating thickness is typically between 100μm and 200μm, although busbars may have considerably thicker coatings of plastic, usually polyamide/nylon (PA).

PROCESSING

  • Requires integration with a galvo scanner for high-speed processing, usually using multiple laser passes.
  • Hairpins are positioned at an angle with respect to the incident beam, turning midway through the process or utilising multiple lasers to ablate all four sides.
  • Power levels from 100 W to 1kW may be used. Cycle time depends on factors including power, spot size and hatching distance and pattern.
  • Due to its high reflectivity at the CO2 laser wavelength, the copper remains undamaged.
  • Results depend on the composition of the coating, with PI being the most problematic. In this case, the process leaves a charred residue.
  • The process often leaves a thin residual layer which cannot be removed by the CO2 laser. In this case, a further processing stage is required, typically using a YAG or fibre laser to remove the residue. PA coatings typically leave no residue and may be ablated using a CO2 laser only.

APPLICATIONS LAB

Our applications lab is equipped with galvo systems at 120W and 450W power levels. If you would like us to test some samples, or if you require further information about this application, please contact sales.support@luxinar.com

Charred residue left after ablating polyimide coating

Most coatings can be ablated without charring

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