KiCad: The Free and Professional PCB Design Tool

Why KiCad? Free and Professional

KiCad is a fully free and open-source PCB design tool with no restrictions on board size or layer count. In the past, designers had to pay thousands of dollars for software like Altium Designer or Eagle. Today, KiCad offers comparable capabilities at no cost.

In industrial environments, KiCad is an excellent choice for several reasons:

No licensing costs, making it suitable for small and medium companies.
An active community and extensive component libraries covering thousands of industrial parts.
Supports board designs with up to 32 layers.
Exports Gerber files compatible with all fabrication houses.
Available on Windows, Linux, and macOS.
CERN (the European Organization for Nuclear Research) supports its development, ensuring long-term continuity.

KiCad version 8 brought significant improvements in performance and user interface, making it a genuine competitor to commercial tools. The interactive router became smarter and now supports differential pair routing.

Installing KiCad and a Tour of the Interface

Installation: Download KiCad from the official site kicad.org. Choose the stable release, not the nightly build. The installation process is straightforward on all platforms. The download size is approximately 2 gigabytes including the core libraries.

Main Interface: When you open KiCad, you see the Project Manager which displays:

Schematic Editor: For drawing electronic schematics. This is where every project begins.
Symbol Editor: For creating new component symbols not found in the library.
PCB Editor: For designing the physical board after completing the schematic.
Footprint Editor: For creating new component footprints or modifying existing ones.
Gerber Viewer: For previewing manufacturing files before sending them to the fab house.
Calculator Tools: Useful calculators for trace width, impedance, and unit conversion.
3D Viewer: For previewing the board in three dimensions, very useful for checking component clearances.

Creating a new project: File > New Project. Choose a dedicated folder and a clear name such as sensor_module_v1. KiCad automatically creates the schematic (.kicad_sch) and board (.kicad_pcb) files.

Tip: Create a separate folder for each project and add it to version control (Git) to track changes.

Drawing the Schematic in Schematic Editor

Basic steps for drawing a schematic:

Adding components: Press A to open the symbol library. Search for a component by name, such as STM32F103C8 or LM7805. Select it and place it on the schematic. The library contains thousands of components organized by type.
Connecting components: Press W to draw a wire. Link component pins together. A connection appears as a green dot at wire junctions. If no dot appears, the wires are not connected.
Adding power flags: Search for VCC, GND, and +24V in the power library. Place them to define power sources and ground. These flags automatically connect all points sharing the same name.
Naming nets: Press L to add a label. Name nets with descriptive names like SPI_MOSI or RELAY_CTRL. Labels connect distant points without drawing long wires.
Adding notes: Use the text tool to document component values and design decisions. For example, write next to a resistor: "R1 = 4.7k for 1-Wire pull-up per DS18B20 datasheet".

Important shortcuts:

M to move a component with connected wires
G to drag a component without wires
R to rotate a component 90 degrees
C to copy a component (useful for repeated capacitors)
E to edit component properties (value, footprint)
Delete to remove a component or wire

Assigning Footprints and Creating the Netlist

After completing the schematic, each symbol needs a physical footprint describing its real shape on the board.

Assigning footprints:

Open the Assign Footprints tool from the Tools menu.
For each component, select the appropriate footprint. For example:
- 10k ohm SMD resistor: choose Resistor_SMD:R_0805 (the most common industrial size)
- STM32 microcontroller: choose Package_QFP:LQFP-48 (48 pins, 0.5mm pitch)
- Terminal connector: choose TerminalBlock:TerminalBlock_bornier-2_P5.08mm
- 100nF capacitor: choose Capacitor_SMD:C_0805 (same size as resistor for assembly simplicity)

Tip: Try to standardize component sizes as much as possible. Using 0805 for all small resistors and capacitors simplifies the soldering and assembly process.

Electrical Rules Check (ERC): Before proceeding, run the Electrical Rules Check from the Inspect menu. It will detect:

Unconnected pins without a No Connect flag
Power source conflicts (two outputs connected together)
Nets without a signal driver (Input without Output)
Power pins without power flags

Fix all errors before moving to board layout. Warnings may be acceptable, but errors are not.

Designing the Board in PCB Editor

Transitioning from schematic to board:

In the Schematic Editor, select Tools > Update PCB from Schematic.
All components appear as footprints with ratsnest lines indicating the required connections. The thin lines are "promises" of connection that need to be turned into copper traces.

Placing components:

Start with connectors at the board edges (they must be accessible).
Place the microcontroller in the center because most signals originate from it.
Position capacitors close to the pins they serve (especially decoupling capacitors).
Respect the required size constraints and mounting holes.
Leave sufficient clearance from board edges (at least 1mm).

Routing traces:

Press X to start routing a trace.
Set trace width: 0.25mm for signals, 0.5mm or more for power.
Use both layers: F.Cu for the front and B.Cu for the back.
Add vias when you need to switch between layers.
Use 45-degree angles instead of 90-degree angles for better electrical performance.

Adding a ground pour:

Draw a copper zone on each side connected to the GND net.
This improves electrical performance, provides a current return path, and helps with heat dissipation.

Exporting Gerber and Drill Files

Gerber files are the standard format understood by every PCB manufacturer in the world:

In the PCB Editor, select File > Fabrication Outputs > Gerbers.
Select the required layers:
- F.Cu and B.Cu: Copper layers
- F.SilkS and B.SilkS: Silkscreen layers (component names)
- F.Mask and B.Mask: Solder mask layers
- Edge.Cuts: Board outline
Click Plot to generate the files.

Drill File:

From the same dialog, click Generate Drill Files.
Select the Excellon format (the standard for all manufacturers).
This defines the locations and sizes of all holes in the board: vias, component holes, and mounting holes.

Final verification:

Open the Gerber Viewer and load all files on top of each other.
Verify that all layers are present and the outline is correct.
Check for broken traces or overlapping issues.
Compress the Gerber files into a single ZIP for sending to the manufacturer.
Many manufacturers (such as JLCPCB) provide instant preview when you upload the file.

Summary

KiCad provides an integrated environment for PCB design from schematic to manufacturing files, at no cost. Mastering the basic tools in KiCad enables you to design professional industrial boards. The key is continuous practice, starting with simple projects and gradually increasing complexity. In the next lesson, we will dive into component placement rules and trace routing for optimal electrical performance.