Types of printed circuit board

One of the simplest printed circuit boards is the double layer board. It has copper on both sides, which are called outer layers;

Multilayer sandwich boards with additional internal layers of copper and insulation are called multilayer.

PCBs can be single-sided (one layer of copper), double-sided (two layers of copper on both sides of an insulating board), or multi-layered (outer and inner layers of copper alternating with insulating layers).

Among the multi-layer PCBs, the most common are the four-layer ones. The four-layer board has many more routing options in the internal layers compared to the two-layer board, and often part of the internal layers are used as a ground plane or power plane, to achieve better signal integrity, higher signaling frequencies, and better power supply decoupling.

In multilayer boards, layers of material are laminated together in an alternating sandwich: copper, substrate, copper, substrate, copper, etc.; each layer of copper is etched and any internal sleepers (which will not extend to both outer surfaces of the finished multilayer board) are plated before the layers are laminated together.

FR-4 epoxy glass is the most common insulating substrate.

Flexible-Rigid printed circuits are boards that bring in a unique combination of superior technology a flexible printed circuit made of a thin polyamide of 0.1-0.3 mm with a rigid printed circuit on an FR4 substrate. These printed circuits are used more and more lately, having the advantage of their flexibility.

A PCB may have an inscription or screen printing that identifies components, test points or identification text. Screen printing does not normally affect the operation of a PCBA.