How is a Microvia produced?
Nowadays microvias are drilled by laser. Here there are different techniques
Shadow mask / CO2 laser: (approx. 350 drill holes per second). An opening is etched in the Cu coating of the outer layer. The CO2 laser burns the dielectric material down to the first inner layer.
UV Laser / CO2 Laser: (approx. 200 drill holes per second). The outer layer Cu is removed by the UV laser in a spiral movement. The CO2 laser burns the dielectric material down to the first inner layer.
UV Laser: (approx. 80 drill holes per second). Both the outer layer Cu and the dielectric material are removed by the Cu laser.
All laser-drilling techniques have advantages and disadvantages
With the shadow mask / CO2 laser, the major advantage is the tremendous speed with which the microvias can be drilled. The disadvantage is that the Cu surface has to be opened with an additional photolithographic process. According to the state-of-the-art, the combination of UV laser / CO2 laser represents the best combination of flexibility and drilling speed.Here the microvias are generated in a single working step. The opening of the Cu surface with the UV laser is very precise. The UV laser alone represents the most technologically flexible variation. The disadvantage is lieslays the relatively low drilling speed.