Method of drilling a circuit board

Abstract

A circuit board comprising a dielectric material provided with a conductive layer is drilled with laser operated at an energy density below the ablation threshold of the conductive layer. The method of drilling includes providing on the conductive layer an ablation layer having an ablation threshold near or below that laser energy density, directing the laser at a target area of the ablation layer to ablate portions of the conductive and dielectric layers in the target area, and removing any remaining ablation layer from the conductive layer.