Current state of laser drilling of µVias in PCB production

The production of via holes for PCBs is an evergreen topic. In the past, CO₂-Laser have been employed for drilling via holes with hole diameters down to about 20 μm. Due to miniaturization and higher interconnect densities, the via hole size has shrunk to about 10 μm for which short-pulsed UV-Laser sources are widely used. The next generation PCBs require even smaller interconnects at significant higher densities: 5 μm hole diameter and tens of millions of holes per PCB substrate. Hole size, quality, position accuracy and production speed demand tightly specified laser sources as well as carefully designed and aligned beam path setups. Furthermore, process monitoring and active feedback-controlled laser drilling are crucial to guarantee highest quality and maintain precise manufacture of the via holes. The miniaturization of via holes in PCBs pose high demands on process quality and stability. Factors such as beam roundness and astigmatism right out of the Laser source now have a significant role for the achievable via hole quality. This work covers the current production demands and their implications on the Laser source, beam manipulation and beam delivery system.