Before the motherboard can begin to take shape, the inner layer must be sheared and drilled. There are about 15,000 holes made in each inner layer motherboard. The process takes around 30 minutes to complete ten 'inner layer' PCBs at a time on each machine.
Here you can see the detail on a defected inner layer - there is simply a mass of holes drilled in the sheet of metal. Once the inner layer has been sheared, they are sent off for copper sheet lamination in a huge clamping machine, capable of laminating a large number of PCBs at the same time.
The PCBs are manufactured in pairs in this particular example, as it helps to save waste. After the lamination process is completed, each pair of PCBs is separated, checked and then re-stacked, ready for routing and edge beveling.