Circuit board glossary

Outer layers


The outer copper layers / conductive patterns of printed circuit boards are refered as outer layers (named top and bottom). A printed circuit board has one  (single-sided PCB) or two (two-sided or multilayer PCB) outer layers, which can be assembled with components.

The thickness of the copper foil (start copper) on the (FR4) material on the outer layers increases by 20 - 25µm through the galvanic procedure of the through-plating process other than on the inner layers.