Picosecond IR Pulsed Laser Drilling of Copper-Coated Glass/Epoxy Composite

Laser drilling has been adapted for forming a hole to connect between layers of multilayered printed circuit board (PCB). Many manufacturers have adapted CO
₂
lasers to achieve process throughputs with blind via hole (BVH) diameter greater than 75 μm. However, slimmer and lighter electronic devices that require sub-50-μm BVHs and CO
₂
laser have a limitation due to the nature of their characteristics. A nearinfrared (IR) laser is a good alternative to form sub-50-μm BVHs, but far too little attention has been paid to BVH drilling with the near-IR laser. This paper applied picosecond IR pulsed laser to create BVH on copper-coated glass/epoxy. Smear zone, top and bottom hole diameters, and taper ratio are investigated as a function of the total fluence. The result shows that the sub-50-μm BVHs can be achieved with picosecond IR pulsed laser.