PCB layout

PCB layout is the second big step: taking the abstract schematic and deciding where, physically, every part and every wire goes on the actual board. If schematic capture is writing the guest list and seating plan in words, layout is walking into the room and placing each chair and each guest at a real spot on the floor. You position the components, then draw the copper traces that connect them, fitting everything into the board's real size while obeying the manufacturer's rules. This is where a design stops being an idea and becomes a thing that can be built.

The workflow starts from the netlist the schematic produced. The layout tool drops in each part's footprint and draws faint rubber-band lines (the ratsnest) showing every connection that still needs a copper trace. You drag parts into a sensible arrangement — related parts together, decoupling caps hugging their chips, connectors at the edges — then route: lay traces on the top and bottom (and inner) layers, dropping vias to hop between layers when paths must cross. All the while a design rule check watches that no two copper features come closer than the fab allows.

Why it matters: layout is where the invisible physics lives. Trace length and width set resistance and inductance; the loop a current makes sets how much noise it radiates and picks up; the gap to the ground plane sets impedance. A great schematic with a careless layout oscillates, overheats, or fails EMC tests. The craft is real: keep high-current and sensitive return currents apart, minimise loop area, place decoupling caps right at the pins, and route fast signals over a continuous ground plane. From idea to copper, this is the step that decides whether the board actually works.