Introduction to PCB design with KiCad version 5.1
In this tutorial we will learn the very basics of using KiCad for designing a circuit board. It is assumed that you already installed KiCad. If not head over to KiCads download page and follow the instructions for your operating system.
This tutorial is split into the following sections:
- Creating a Project
- Designing the schematic (Schematic using symbols and Wires)
- Lay out the board (Visibility options, Footprints, Traces and board outline)
- Improve the schematic (Power symbols, labels and electrical rule check)
- Improve the Layout (Updating from schematic changes, copper zones, vias, net selection and exchanging units)
- Get ready for manufacturing (Design rules and gerber export)
What is needed for a PCB to be produced?
A Printed Circuit Board (PCB) is defined by a number of layers. These layers include a defined number of copper layers, solder-mask, silkscreen and board edge which are required by the board house to manufacture your board. Additional layers like the fabrication and courtyard layers are there to document your board or help with ensuring manufacturing constrains are met.
The PCB Layout software uses footprints that define the interface with every component. Pads in a footprint define the places where the leads are soldered to by defining a copper geometry, soldermask cutout, paste stencil cutout and if necessary a drill hit. Graphics on technical layers help for documentation like silkscreen. And graphics on the courtyard layers ensure that no other component is placed to close.
To define which pads need to be connected with traces (or other means) you use the connectivity information that you get from the schematic. This connectivity information is also called a net-list (it is a list of nets plus defines which pad is assigned to which of these nets).
The schematic is build up from symbols that are the abstract view of the function of every component (The schematic is then the abstract view of the systems intended function) Symbols define pins that are mapped to footprint pads (via the pin/pad numbers and the footprint field of the symbol). You define the connectivity information by using wires that are used to connect pins together. (or you can also use labels or power symbols)
A schematic can additionally contain information for creating a bill of materials. This information is contained in additional symbol fields.
The design flow
The design process goes the other way round than this introduction. One starts with an abstract idea for the system (your customers specification, your own idea about what you want to achieve, …)
This specification is then converted to a schematic view of the solution to the given problem. Part of the schematic design is to select the components that you use for making the system. (In this step you need to ensure that you can buy the required parts.)
The schematic is used to define the connectivity of the layout. In the layout tool you then finally define the layers required by the board house by using footprints and the connectivity information that is used to define the copper layers.
The tutorial here does not go into details how to get from the abstract idea to the schematic nor do we show how to select components. It shows you how to use KiCad to get from this known information to the final product.