It is to subsequently drill the holes within the multilayer PCB via the drilling machines.
![](https://pcbweller.com/app/uploads/2020/11/PCB-drilling-hole-process.png)
This process must be highly optimised so that it can meet the registration positional accuracy to all of the the inner layer connections.
![](https://pcbweller.com/app/uploads/2020/11/PCB-drilling-hole-process-illustration.png)
Eexcept the mechanical drilling process,the drilling can also be done by a laser drill for blind holes (LASER CO²+LASER UV).
![](https://pcbweller.com/app/uploads/2020/10/hitachi-PCB-drill-machine.jpg)