Copper Direct Drilling With TEA$hbox CO_2$Laser in Manufacture of High-Density Interconnection Printed Circuit Board

A method for copper direct drilling by carbon dioxide
$(hbox CO_2)$
laser was investigated for efficient microvia formation on the copper conducting layer of high-density interconnection (HDI) of printed circuit board (PCB). A metal–tin layer was coated on the surface of copper conductor foil to enhance the
$hbox CO_2$
laser energy adsorption on it. The coated surfaces were then drilled by a
$hbox CO_2$
laser with various pulse energies. The microvia holes were efficiently formed in good quality with one laser pulse on 9-
$muhbox m$
-thick polished copper conducting layer. The laser energy absorption of coated copper foils was approximately calculated. The experimental results demonstrated the potential application of the developed method in high-density interconnection printed circuit board manufacturing.