With the schematic completed, go back to the Project Window and open the PCBEditor, either by clicking the PCB Editor button or opening the board file.
PCB Editor Basics
Navigation in the PCB Editor is the same as the Schematic editor: pan bydragging with the middle mouse button or right mouse button, and zoom with thescrollwheel or F1/F2.
The main part of the PCB Editor is a canvas where the board will be designed.The toolbar on the left side has various display options for the board,including units and toggles for outline/filled display modes for tracks, vias,pads, and zones. The toolbar just to the right of the canvas contains tools fordesigning the PCB.
Some buttons on the right toolbar have a small triangle in the bottomright corner  . The triangleindicates that the button has an expanding palette containing severalrelated tools, for example different kinds of dimensions. To select analternate tool, click and hold on the button until the palette appears,then click on the alternate tool. Another way to use the palettes is toclick on the button and drag to the left until the palette appears, thenrelease the mouse button when the desired tool is highlighted. |
At far right is the Appearance Panel and Selection Filter. The Appearance panelis used to change visibility, colors, and opacity of PCB layers, objects, andnets. The active layer is changed by clicking on the name of a layer.
Below the Appearance Panel is the Selection Filter, which enables and disablesselection of various types of PCB objects. This is useful to select specificitems in a crowded layout.
Board Setup and Stackup
Before designing the board, set the page size and add information to the titleblock. Click File → Page Settings…, then choose an appropriate papersize and enter a date, revision, and title.
Next, go to File → Board Setup… to define how the PCB will bemanufactured. The most important settings are the stackup, i.e. what copper anddielectric layers the PCB will have (and their thicknesses), and the designrules, e.g. sizes and spacing for tracks and vias.
To set the stackup, open the Board Stackup → Physical Stackup page ofthe Board Setup window. For this guide, leave the number of copper layers at 2,but more complicated projects might require more layers.
Next, go to the Design Rules → Constraints page. The settings on thispage specify the overriding design rules for everything in the board design. Forthe purposes of this guide, the defaults are fine. However, for a real projectthese should be set according to the capabilities of the PCB fab house so thatthe PCB design is manufacturable.
Finally, open the Design Rules → Net Classes page. A net class is a setof design rules associated with a specific group of nets. This page lists thedesign rules for each net class in the design and allows assigning nets to eachnet class.
Track width and spacing can be managed manually by the designer during layout,but net classes are recommended because they provide an automatic way to manageand check design rules.
In this design, no net classes are specified, so all nets will belong to theDefault net class. The default design rules for this net class areacceptable for this project, but other designs may have multiple net classes,each with different design rules. For example a board might have a HighCurrent netclass with wide traces, or a 50 ohm netclass with specific widthand clearance rules for 50 ohm controlled-impedance traces.
Importing Changes From Schematic
The schematic is complete, but there are not yet any components in the layout.To import design data from the schematic into the layout, click Tools →Update PCB from Schematic…, or press F8. There is also a button
in the top toolbar.
Read through the messages in the Changes To Be Applied window, which willsay that the three components in the schematic will be added to the board. ClickUpdate PCB, Close, and click on the canvas to place the threefootprints. The location of each footprint relative to the others will bechanged later.
In KiCad, updating the PCB with changes in the schematic is a manual process:the designer decides when it is appropriate to update the PCB with modificationsin the schematic. Each time the schematic is edited, the designer must use theUpdate PCB from Schematic tool to keep the schematic and layout in sync.
Drawing A Board Outline
Now the three components have been placed, but the board itself has not beendefined. The board is defined by drawing a board outline on the Edge.Cutslayer.
It’s often useful to draw the board outline with a coarse grid, which makesit easy to get round numbers for the board size. Switch to a coarse grid byselecting 1mm in the Grid dropdown menu above the canvas.
To draw on the Edge.Cuts layer, click Edge.Cuts in the Layers tab of theAppearance panel at right. Choose the rectangle tool
in the right toolbar, click on the canvas toplace the first corner, then click again to place the opposite corner so thatthe rectangle roughly surrounds the three footprints. The other graphic tools(line 
, arc 
, circle
, polygon
, or a combination of them) couldalso be used to define the board outline; the only requirement is that theoutline is a single closed shape that doesn’t intersect itself.
Placing Footprints
The next step in the layout process is to arrange the footprints on the board.In general, there are a several considerations for positioning footprints:
Some footprints may have exact requirements for their locations, such asconnectors, indicators, or buttons and switches.
Some components may need to be placed according to electrical considerations.Bypass capacitors should be close to the power pins of the associated IC andsensitive analog components should be far from digital interference.
Almost all components have a "Courtyard" (or two if both Front and Back aredefined). Generally Courtyards should not intersect.
Otherwise components should be positioned for ease of routing. Connectedcomponents should generally be close together, and arranged to minimizerouting complexity. The ratsnest (the thin lines indicating connectionsbetween pads) is useful for determining how best position footprints relativeto other footprints.
For the purposes of this guide, the only placement goal is to make the routingprocess as simple as possible.
Start by moving the battery holder BT1 onto the back side of the board. Clickit to select it, then press M to move it. Press F to flip it to theopposite side; it now appears mirrored and its pads have changed from red toblue.
All PCB layers are viewed from front side of the board. Footprints on the bottomof the board are therefore upside down and appear mirrored.
Each PCB layer has a unique color, which is shown by the swatches in the Layerstab of the Appearance panel. In the default color scheme, items on the F.Cu(Front Copper) layer are red, while items on the B.Cu (Back Copper) are blue.
Now place the other two components. One at a time, select each component, thenmove and rotate it with M and R. Watch the ratsnest lines betweeneach pad to choose the simplest arrangement of components; a good arrangementwill leave the lines untangled. One possible arrangement is shown in thescreenshot below.
Routing Tracks
With the components in place, it’s time to connect the pads with copper traces.
The first trace will be drawn on the front of the board, so change the activelayer to F.Cu in the Layers tab of the Appearance panel.
Click Route Tracks 
in the right-handtoolbar or press X. Click on the led pad of D1. The ratsnest lineindicates there is an unrouted connection to the led pad of R1, so click onthat pad to draw a trace connecting the two pads. Clicking on the second padcompletes the trace. The ratsnest line between the led pins is no longer drawnbecause the connection has been made in copper.
Now draw a trace between the GND pads of BT1 and D1, starting with the BT1pad on the back of the board. Notice that the active layer automatically changedto B.Cu after clicking on the BT1 pad. Click on the D1 pad to finish thetrack.
While BT1 has surface mount pads that are only on the bottom of the board,D1 has through hole pads that can connect to tracks on both the front andback. Through hole pads are one way to make a connection between multiplelayers. In this case, D1 is a component on the front side of the board, butit* through hole pads are used to connect to a trace on the back of the board.
Another way to make a connection across layers is with a via. Start routing at theVCC pad of BT1 on the back of the board. Press V and click halfwaybetween BT1 and R1 to insert a via, which also switches the active layer toF.Cu. Complete the track on the top side of the board by clicking on theVCC pad of R1.
At this point, all connections are routed. This can be confirmed by looking atthe status screen in the bottom left of the window, where the number of unroutednets is given as 0.
Placing Copper Zones
Copper zones are regions of copper with an associated net. Zones automaticallyconnect to copper objects belonging to the same net and avoid objects belongingto other nets. Zones are often used for ground and power connections because theyprovide a lower impedance connection than traces.
Add a GND zone on the bottom of the board by switching to the bottom copperlayer and clicking the Add a filled zone button
in the right toolbar. Click on the PCB to placethe first corner of the zone.
In the Copper Zone Properties dialog that appears, select the GND net and makesure that the B.Cu layer is selected. Click OK, then click to place the otherthree corners of the zone. Double click when placing the last corner to completethe zone.
The zone outline is displayed on the canvas, but the zone is not yet filled — there is no copper in the zone area, and therefore the zone is not making anyelectrical connections. Fill the zone with Edit → Fill All Zones(B). Copper has been added to the zone, but it doesn’t connect to theVCC or led pads and traces, and is clipped by the board edge. It overlapswith the GND trace drawn earlier, and it connects to the GND pads throughthin traces. These are thermal reliefs, which make the pads easier to solder.Thermal reliefs and other zone settings can be modified in the zone propertiesdialog.
In KiCad, zones are not filled automatically when they are first drawn ormodified, or when footprints within them are moved. Zones are refilled bymanually filling them and when running DRC. Make sure zone fills areup-to-date before generating fabrication outputs.
Sometimes filled zones can make it hard to see other objects in a crowded boarddesign. Zones can be hidden except for their boundaries using the Show onlyzone boundaries button 
on theleft-hand toolbar. Zones retain their filled status when only their outlines areshown — hiding a zone fill is not the same as unfilling it.
Zones can also be made transparent using the Appearance panel, and inactivelayers can also be hidden or dimmed using the Layer Display Options in theAppearance Panel.
Design Rule Checking
Design Rule Checking is the layout equivalent of Electrical Rule Checking forthe schematic. DRC looks for design mistakes like mismatches between theschematic and layout, copper regions that have insufficient clearance or areshorted together, and traces that do not connect to anything. Custom rules canalso be written in KiCad 8.0. To view the full list of design rules that arechecked and to adjust their severity, go to File → Board Setup… →Design Rules → Violation Severity. Running DRC and fixing all errorsis strongly advised before generating fabrication outputs.
Run a DRC check with Inspect → Design Rules Checker, or use the button
in the top toolbar. Click Run DRC. When thechecks are complete, no errors or warnings should be reported. Close the DRCwindow.
Now intentionally cause a DRC error by moving the resistor footprint to overlapthe filled area of the zone. Use D (Drag) to move the resistor footprintslightly while keeping the traces attached to its pads. This creates a clearanceviolation because the VCC and led pads of the resistor are shorted to theGND zone fill. Ordinarily this would be fixed by refilling the zone, but don’trefill the zone yet.
Run DRC again, but make sure to uncheck the Refill all zones before performingDRC checkbox. DRC reports 6 violations: for each pad of R1, there is aclearance violation between the pad and the zone, another clearance violationbetween the pad’s through hole and the zone, and a third violation where thepad’s solder mask opening exposes the copper of two different nets (the GNDfill and the trace connected to the pad). Arrows point to each violation in thecanvas. Clicking on each violation message zooms in on the respectiveviolation.
Close the DRC dialog, press B to refill the zone, and re-run DRC.Alternatively, check the Refill all zones before performing DRC checkbox andre-run DRC. All violations are fixed.
3D Viewer
KiCad offers a 3D viewer that is useful for inspecting the PCB. Open the 3Dviewer with View → 3D Viewer. Pan by dragging with the middle mousebutton, and orbit by dragging with the left mouse button. Orbit around the PCBto see the LED and resistor on the top, and the battery holder on the bottom.
A raytracing mode is available, which is slower but offers more accuraterendering. Switch to the raytracing mode with Preferences →Raytracing.
Many of the footprints in KiCad’s library come with 3D models, including all ofthe footprints used in this guide. Some footprints do not come with 3D models,but users can add their own.
Fabrication Outputs
With the board design finished, the final step is to generate fabricationoutputs so the board can be manufactured.
Open the Plot dialog with File → Plot…. This dialog can plot thedesign in several formats, but Gerber is usually the right format for orderingfrom a PCB fabricator.
Specify an output directory so that the plotted files will be collected in afolder. Otherwise, the default settings are fine, but make sure all the necessarylayers are checked: include the copper layers (*.Cu), board outline(Edge.Cuts), soldermask (*.Mask), and silkscreen (*.Silkscreen).The paste layers (*.Paste) are useful for manufacturing solder pastestencils. The Adhesive layers (*.Adhesive) are needed only if anycomponents will be glued to the board during assembly. Other layers may beuseful to plot, but are not typically necessary for PCB fabrication.
Click Plot to generate the Gerber files. Also click Generate DrillFiles… and then Generate Drill File to create files specifying thelocation of all holes that will be drilled in the board. Finally, close the Plotdialog. The design is finished.
