How a flat sheet becomes a circuit
A circuit board is a wiring system built into a solid panel. Its copper traces—the narrow conductive paths—carry signals and power between components, while the surrounding fiberglass-and-resin laminate keeps those paths apart and supports the parts mounted on the board.
To define a pattern, manufacturers cover copper with a light-sensitive coating, expose selected areas through a mask, and wash away the coating where copper should be removed. An etching solution dissolves the exposed metal. What remains is a deliberately shaped network, not a continuous sheet.
Why build the board in layers?
A simple board can route everything on one or two copper faces. A more complex design may need several copper layers so that many connections can fit in a compact area without crossing one another. Insulating sheets separate the layers; heat and pressure bond the stack into one rigid panel as the resin cures.
Connections between layers are made through vias: small holes drilled through the board and lined with copper. That lining lets current pass from one layer to another, much like a short vertical section of wire. The holes and copper patterns must line up, so layer placement is a manufacturing constraint as well as a design choice.
The finished board is therefore more than plastic with metal attached: it is a precisely arranged set of insulated routes, joined where needed. That hidden wiring lets a device pack far more connections into a small space than loose wires could.
