KiCad

KiCad covers the path from a circuit idea to the files a board house needs. The schematic editor and the board editor are separate programs sharing one project: symbols are placed and wired in the first, footprints are assigned to them, and the resulting connectivity is carried across to the second, where parts are positioned on the board and copper tracks are routed between them.

The board editor works with copper layers, silkscreen, solder mask and board outline, and its interactive router can push existing tracks aside as you draw a new one. Design rule checking reports clearance and connectivity problems on the board, and an electrical rules check does the equivalent on the schematic. A 3D viewer renders the assembled board from models attached to the footprints, and the finished design goes out as Gerber and drill files, with a separate viewer for inspecting those.

Symbol, footprint and 3D model libraries ship with the suite and can be extended with your own. The schematic editor drives ngspice for simulation, and the board editor exposes a Python API for scripted edits.