What is a PCB?

Open up almost any electronic device and you'll find a flat, usually green board covered in tiny parts. That's a printed circuit board, or PCB. It does two jobs at once: it holds the parts in place, and it connects them with thin copper paths instead of loose wires.

The layers of a board

A basic PCB is a sandwich:

• Core (substrate). A stiff sheet of fiberglass and epoxy called FR-4, usually 1.6 mm thick. It's the board's skeleton and doesn't conduct electricity.
• Copper. Thin sheets of copper bonded to one or both sides. Most of it is etched away, leaving only the paths you designed.
• Solder mask. The colored coating (green by tradition) that covers the copper so solder only sticks where it should, and so nearby paths don't short together.
• Silkscreen. White printed text and outlines: part names like R1 or U1, the board name, and arrows showing which way parts go.

A 2-layer board has copper on both sides. A 4-layer board adds two more copper sheets inside the sandwich, which gives you more room for connections and a cleaner power supply. Most hobby projects fit on 2 layers.

Traces, pads and vias

The copper that's left after etching takes three shapes:

• Traces are the wires: flat copper paths running from one part to another. Wider traces carry more current.
• Pads are exposed copper spots where a part's legs or contacts get soldered.
• Vias are tiny plated holes that connect a trace on the top layer to a trace on the bottom layer, like a staircase between floors.

A net is everything that should be electrically connected: for example, every pad that touches 3.3 V. Designing a board is mostly making sure each net is connected and nothing else is.

Through-hole vs. surface mount

Parts attach in one of two ways:

Type	How it attaches	Good for
Through-hole (THT)	Legs go through holes and get soldered on the far side	Connectors, big parts, easy hand soldering
Surface mount (SMD)	Flat contacts sit on pads on the surface	Small, cheap, machine-assembled boards

Modern boards are mostly surface mount. That's why Kiln Forged boards are designed to arrive already assembled by the manufacturer: you don't have to hand-solder parts smaller than a grain of rice.

From design to a board in your hand

1. Schematic. A diagram of which parts connect to which. (See Reading a schematic.)
2. Layout. Placing the parts on a board outline and routing the traces.
3. Design rule check (DRC). Software checks that traces aren't too close, holes aren't too small, and every net is connected.
4. Gerber files. The standard manufacturing files, one per layer. Any board maker accepts them.
5. Fabrication and assembly. A factory etches the copper, applies the mask and silkscreen, then a machine places and solders the parts.

For a small board, a batch of five usually costs a few dollars each and arrives in about a week.

Where Kiln Forged fits in

When you describe a device, the circuit board engine does steps 1 to 4 for you: it picks parts, draws the schematic, lays out the board, runs the design rule check, and exports a KiCad project plus Gerbers. In the workspace's Why panel it tells you why each part was chosen, so the board isn't a mystery when it arrives.

Try it: open the IR Remote Cloner demo and look at the circuit board stage. Every label on the board (U1, Q1, D1…) is a part in the parts list.