Laser removal of molded flashes from a leadframe heatsink surface

Epoxy residues on a leadframe heatsink surface of a molded integrated circuit package are a major concern for the subsequent solder plating process. Studies using a pulsed green laser to remove the epoxy residues from precoated copper-based leadframes were carried out. Effects of the laser beam mode profile and process variables on the effectiveness of residue removal and surface morphology of the heatsink were investigated. Ring marks that appeared on the laser-irradiated area were analyzed by secondary ion mass spectroscopy to determine the depth profiles of the layered structures. Calculations were carried out to estimate the temperature rise in the surface due to the laser irradiation. It is concluded that laser deflashing can be a process suitable for production uses.