How is the Number of PCB Layers Counted? What is the Difference between Double Sided PCB and Multi-layer PCB?

“PCB Layer Count”
The number of PCB layers depends on its copper layers. For instance, if the design contains only one layer of copper then it is a single sided PCB; if it contains two layers of copper then it becomes a double sided PCB. If there’re more than two layers of copper, we call it a Multi-layer PCB. Please refer to the image below.

“Multi-layer PCB Production Process”
How do PCB manufacturers produce Multi-layer PCBs? Take below six layer board for example, PCB manufacturers has to first complete inner layer; then stack up the completed inner layer by placing prepreg in between. Once all layers are in correct position, then laminate all layers into one.




“Double sided PCB vs. Multi-layer PCB”
The difference between double sided PCB and Multi-layer PCB is that double sided PCB has no inner layer and lamination process.

“Single sided PCB vs. Multi-layer PCB”
On the other hand, there’s no inner layer and PTH process in single sided PCB.