Did you really know what are multilayer PCBs’ hole?

Why we discuss the hole of multilayer PCBs?

What are multilayer PCBs is a very big question for the PCB industry.
Not only due to complex construction of multilayer PCB, but also the manufacture process, especially the hole of the multilayer PCBs.
So this post will focus on the hole of multilayer PCBs.

The holes of multilayer PCBs were different with 2 layer PCB

If you have know the hole of 2 layer PCB or called double sided PCBs, you must know those hole always through the whole board, and most those holes have plated copper.
But if you scan the multilayer PCBs, you will find the holes were very different from 2 layer PCB.
There were many types of hole on multilayer PCBs.
Some of them were through whole layers of the board, but some were not.

The whole of multilayer PCBs you should know

If you ask a rich experience PCB expert what is the most complex process during multilayer PCBs.
You likely get the multilayer PCB hole process manufacturer.
‘Buried ‘ and ‘Blind ‘ vials avoid this problem because they only penetrate as many layers as necessary.
The blind was connecting one or more of the inner layers with one of the surface layers without penetrating the whole board.
Buried was only connect inner layers.
Did you really know what are multilayer PCBs' hole?