Beginners Guide: PCB Design
William Zyhowski, December 2023
Last updated
William Zyhowski, December 2023
Last updated
This is a beginner’s guide to PCB design. It serves only to provide a general idea of the tools and methods required to design simple PCBs. As always, more complex projects will call for additional study and, possibly, the assistance of individuals with technical expertise.
A printed circuit board (PCB) is a medium used to connect or "wire" components to one another in a circuit. It takes the form of a laminated sandwich structure of conductive and insulating layers: each of the conductive layers is designed with a pattern of traces, planes, and other features (similar to wires on a flat surface) etched from one or more sheet layers of copper laminated onto and/or between sheet layers of a non-conductive substrate.
Fusion 360 (formerly Eagle)
SolidWorks PCB
Altium
PADs Professional (Siemens)
These CAD programs output a Gerber file which is an open, ASCII, vector format for PCB design. It is the standard used by the PCB manufacturing industry to describe the entirety of the PCB.
https://www.youtube.com/watch?v=_jgUZeBiusw&list=PLmA_xUT-8UlL80Xm8Gxz98YNum3I9GInr&index=1 (Fusion 360)
https://www.youtube.com/watch?v=ZS-IN8yQex0&list=PLI35xrqqQVUvPAE5GMH__RzJB-13ouqMW&index=1 (SolidWorks)
Depending on the application different substrates are needed. Research what works best for your design. The most commonly used substrate is FR-4, and you will most likely use that for your simple PCB.
FR-2
FR-4
Aluminum
Flexible substrates
Other Uncommon
A printed circuit board can have multiple layers of copper which almost always are arranged in pairs. The number of layers and the interconnection designed between them (vias, PTHs) provide a general estimate of the board complexity. Using more layers allows for more routing options and better control of signal integrity but is also time-consuming and costly to manufacture.
Solder mask – layer on top of the copper foil that insulates the copper traces.
Silkscreen – usually a white layer applied to the top of the solder mask. It adds letters, numbers, and symbols to aid in assembly and indicate the function of components.
Copper Thickness (weight) – The thickness of PCBs can be specified directly or as the weight of copper per area (in ounce per square foot) which is easier to measure. Copper is the most common conductor used in PCBs, but other conductors are options such as gold and silver.
Substrate – a dielectric material most commonly composed of epoxy resin and glass fiber weave. The material chosen will determine the mechanical, thermal, and chemical properties of the circuit board.
1 oz/ft^2 is the standard copper thickness (weight) designation in the United States. Other thicknesses are listed but are less often used.
Through-hole (Thru-hole) components – electrical components that have leads that are inserted into through holes in the PCB and soldered to pads on the opposite side. They are relatively easy to work with and solder but are larger components.
SMD (Surface Mount Device) – An electronic component that mounts on the surface of the PCB. Comes in many packages (shape, size). They are more difficult to solder and work with but take up less space.
Annular ring – the ring of copper around a plated through hole in a PCB
Finger – exposed metal pads along the edge of a board, used to create a connection between two circuit boards.
Pad – a portion of exposed metal on the surface of a board to which a component is soldered.
Panel – a larger circuit board composed of many smaller boards that will be broken apart before use.
Paste stencil – a thin, metal (or sometimes plastic) stencil that lies over the board, allowing solder paste to be deposited in specific areas during assembly.
Plane – a continuous block of copper on a circuit board, defined by borders rather than by a path. Also commonly called a “pour”.
Plated through hole – a hole on a board that has an annular ring, and which is plated all the way through the board. May be a connection point for a through hole component, a via to pass a signal through, or a mounting hole.
Trace – a continuous path of copper (or other conductive metal) on a circuit board. The trace is described by its width. The depth is set by the board's weight (copper weight/thickness)
Via - a hole in a board used to pass a signal from one layer to another. Tented vias are covered by solder masks to protect them from being soldered too. Vias where connectors and components are to be attached are often untended (uncovered) so that they can be easily soldered.
DRC – design rule check. A software check of your design to make sure the design does not contain errors such as traces that incorrectly touch, traces too skinny, or drill holes that are too small.
Drill hit – places on a design where a hole should be drilled, or where they were drilled on the board.
Selection of the copper weight and trace width can be a complex process depending on the application of the PCB. The best practice is to follow the industry standards of IPC–2221 for generic designs and tailor the design based on standards for more sophisticated designs. In general, the more current needed the thicker the trace. Once the trace becomes too large it is better to use a higher weight board to reduce the width of the trace.
https://www.4pcb.com/trace-width-calculator.html
https://resources.altium.com/p/ipc-2221-calculator-pcb-trace-current-and-heating
Autorouter – most PCB design software offers some form of auto trace routing. This should work fine for simple boards, but this is not a perfect tool.
Manufacturer’s specifications – each manufacturer will list specifications such as minimum trace width, minimum trace spacing, number of board layers, etc. You must look these up or risk a board having defects or wasting your time on redesigning the board.
Component Placement – is important for many reasons. It will make it easier to route traces. Try rotating components for optimal trace pathing. Heat dissipation is another issue. Some components are sensitive to heat or require more cooling. Be sure to check the component specifications. Some components are sensitive to EMF and must be placed away from EMF-generating devices. A good example of this would be keeping high-frequency digital components away from analog components.
45-degree trace angles – most design software has 45-degree trace corners set to default. This is because it is harder to manufacture 90-degree trace angles which can produce defects such as a narrower etching.
Utilize the silk layer – the silk layer allows you to label parts and sections of the PCB. This will aid in component placement and troubleshooting. Just be mindful not to over-label and clutter the board with unnecessary information.
https://www.youtube.com/watch?v=35YuILUlfGs
https://www.youtube.com/watch?v=MsdJgEinb34
https://www.youtube.com/watch?v=aODkA2mrimQ
There are many PCB manufacturers to choose from. Some are cheaper than others and located in different countries such as China (PCBWay). The lead time for most PCBs is a few days and then it might require a week or two for shipping if ordered internationally. Just keep that in mind if it is a time-sensitive project.
PCBWay
DigiKey
JLCPCB
OSHPark
Note: Be mindful of some manufacturers that are located in export-controlled countries and some companies have no issues stealing your design. If you have a proprietary design, find a trusted local company so your intellectual property is not stolen. If you are working with any kind of export-controlled product you probably already know that you can get into a lot of trouble if you send your work to an export-controlled country without proper authorization.
PCB design is a fun skill to learn that requires time to understand and practice to hone. You need to familiarize yourself with the design program you want to use and understand best practices depending on your application. This will require further research or even the involvement of someone with technical expertise. Just take your time and do your due diligence.
