3.PCB Layout

Objective

In this final section, you will import your physical components, draw the boundaries of your circuit board, and route the electrical traces.

Getting to Know the PCB Editor

The PCB Editor translates your electrical connections into physical copper. You will primarily use two layers: Edge.Cuts for the physical board shape, and F.Cu (Front Copper) for the electrical traces.

Opening the PCB Editor

There are two ways to open the editor. From your current schematic, we can select the green button in the toolbar to switch into the PCB Editor. Or in the project tree select the .kicad_pcb file.

The Top Toolbar: Integration and Checks

Update PCB from Schematic: (The icon with a schematic pointing to a green board). This is the bridge between your files. It pulls all your assigned footprints and wired connections from your schematic directly onto the physical canvas.
Design Rules Checker (DRC): (The checklist with a red checkmark). This is the physical equivalent of the ERC. It scans your board for manufacturing errors, such as copper traces overlapping or being placed too close to the edge of the board.
3D Viewer: (The 3D board icon). This renders a realistic 3D model of your current layout, allowing you to visually verify the physical placement of your components.

The Right Toolbar: Layout and Routing

Selection Tool: The default cursor. Use this to click, drag, and rotate (using the R key) your physical components.
Route Tracks: The primary layout tool. Use this to draw the physical copper traces between component pads.
Draw a Rectangle: The mechanical drafting tool used to define the physical outer boundary of your board.

The Appearance Panel: Managing Layers

A printed circuit board is manufactured in distinct physical layers, much like a sandwich. This panel controls which layer you are currently drawing on.

Exercise: Continue with your first schematic Blinking LED

Step 1. Import Components

Navigate to the Top Toolbar and click the Update PCB from Schematic icon.
Leave all the settings as is. Click Update PCB in the dialog window.
Your components will appear attached to your cursor. Click anywhere on the black canvas to place them.

Tip: Don't forget to periodically save your work as you go by selecting File > Save or Ctrl + S.

Step 2. Draw the Board Edge

In the Appearance panel on the far right, click on the Edge.Cuts layer to make it active.
Select the Draw a Rectangle tool from the Right Toolbar.
Click and drag to draw a box that completely surrounds your components. This is the physical edge of your board.

Tip: To center your components in the middle of the screen you can click the Zoom to Fit icon in the top toolbar. It looks like a magnifying glass with a square inside.

Step 3. Arrange the Components

Before routing traces, you must physically arrange the parts to make wiring as simple as possible.

Ensure the Selection Tool (the standard cursor) is active on the Right Toolbar.
To make things easier, highlight all of the components, then click and drag them all outside your board edge.
Click and drag your components individually to separate them. Note the red square in the picture on the middle right. The Conn_01x02_Pin Component was selected and rotated to avoid the ratslines crossing.
Arrange them logically: place the connector (J1) near where the edge of the board will be, and position the resistor and LED so the thin ratlines do not cross over each other unnecessarily.
Your circuit might look something like the picture on the bottom right.

Tip: Just like in the schematic editor, you can select a component and press (R) on your keyboard to rotate it.

Picture referenced in step 3.2.

Picture referenced in step 3.3.

Picture referenced in step 3.5.

Routing the Copper Traces

Notice the thin, straight lines (ratlines) connecting your component pads. These represent the logical connections from your schematic. Your goal is to trace these lines with physical copper, adhering to two critical physical rules:

Rule 1: Traces Cannot Cross. Unlike the schematic editor, drawing one trace over another on the same layer (F.Cu) fuses the copper together, creating a short circuit. You must navigate around pads and other traces.
Rule 2: Avoid 90-Degree Angles. When a trace needs to change direction, do not use a sharp, 90-degree corner. Instead, use a 45-degree angle. Sharp corners can cause physical defects during the manufacturing etching process. (Note: Straight traces are perfectly fine; this rule only applies when bending the trace).

Step 4. Route the Copper Traces

In the Appearance panel, click on the F.Cu layer to make it active.
Select the Route Tracks tool from the Right Toolbar or use keyboard shortcut (X).
Click on a component pad, follow the path of the ratline, and click the destination pad to lock the trace in place. If you need to turn, click once on the canvas to anchor the trace, then move your mouse to create a 45-degree bend.
Repeat this until no thin ratlines remain. Your finished product might look like the picture shown on the bottom right.

Step 5. Verifying the Physical Board (DRC)

Before finalizing your design, you must ensure your copper traces do not violate physical manufacturing constraints, such as being placed too close together or too near the edge of the board.

Navigate to the Top Toolbar and click the DRC icon (the checklist with a red checkmark).
Click Run DRC in the dialog window.
The software will scan your physical layout. If you followed the routing rules, the window should return zero errors. If an error appears (such as a trace touching a pad it shouldn't), use the Selection Tool to adjust the trace and run the DRC again until the board is clear.

Step 6. View Your 3D Board!

You have successfully designed a printed circuit board! To see what your physical board will look like once manufactured:

Navigate to the Top Toolbar and click the 3D Viewer icon (it looks like a green 3D board), or simply press Alt+3 on your keyboard.
A new window will open showing a photorealistic 3D render of your PCB.
Click and drag to rotate the board, inspecting your routed copper traces and physical components.
Once you are finished admiring your work, close the 3D Viewer and save your .kicad_pcb file.
Don't forget to Save all of your work before you close the program, you wouldn't want all your beautiful progress to be lost!

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