This post topic is design PCB.
In fact we have shared many articles about the design PCB process.
If you have read HTD circuits shared articles.
You may know the PCB designing process also very complex.
So we are going to focus on layer count factors of design PCB.

First factor is the Layer Count of printed circuit board.
You know the circuit boards have many kind layers.
And different layers have different design way.

The number of layers is also a significant cost-determining factor. 
On of reason is the design PCB method have a different way.
Or some type layers PCB must ask a rich experience PCB designer to do.

Single-sided or double-sided PCBs are roughly the same cost to manufacture. 
So those two type design PCB almost design in same way.
However multi-layer PCBs create additional costs in the materials and manufacturing process.
Add more materials means require to design a PCB different from the single layer PCB.
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