After you have planned your circuit, created the schematics, and tested it on a prototype board, it is time for the critical steps of printed circuit board design (also known as printed circuit board routing). Printed circuit board design is the process of laying out your circuit as it would be on a real-life printed circuit board.
Design is always carried out on PCB routing software.
The design process is imperative for the success of your printed circuit boards. Get it wrong, and you may end up with a low functioning and unreliable printed circuit board.
In this article, we’ll walk through ten proven tips and tricks for great printed circuit board design/layout.
1. Don’t Rush To Use The Autorouter
Most printed circuit board design software have an autoroute feature that automatically does the routing for you. But do not get too excited about this tool because autorouting is not a perfect replacement for routing yourself.
There are a few scenarios where you should use autorouting. These scenarios include:
- After placing all your components, you can use the autoroute tool to check your completion rating. If it is anything below 85%, then you need to adjust your component placement.
- Bottlenecks and other critical connection points may fall through the cracks when routing. You can easily identify these using the autoroute feature.
- Finally, if you don’t know how to begin routing or you get stuck at some point, autorouting can be used as a source of inspiration.
Outside of these scenarios we recommend not using the auto routing feature. Autorouting is not always accurate and it can often ignore symmetry. So if you are a fan of symmetry, then it’s best to do the routing yourself.
In summary, because routing is a science, as well as an art, we recommend manually routing your printed circuit board when you can for both accuracy and reliability. Autorouting should ultimately be used for guidance.
2. Use Sufficient Trace Width
Wouldn’t it be wonderful if the current-carrying copper traces on a printed circuit board could perform their duty unhindered? However, the reality is that these traces have inherent electrical resistance. So when current flows through them, there is a voltage drop, power is dissipated, and heat is generated.
You want to avoid excess heat in your circuit. To reduce the amount of heat build up, traces’ resistance must be reduced by increasing the width of the traces.
Your estimated current must be taken into account while adjusting trace width. To calculate the suitable trace width for your printed circuit board, you can use a trace width calculator. Just input the estimated current and the thickness of your traces, and voila! A suitable trace width value is calculated. As long as it is in line with your manufacturer’s specifications, feel free to use larger trace widths than stipulated by the calculator. The wider your traces are, the lower the possibility of you receiving a board with problematic connections.
3. Know Your Manufacturer’s Specifications
Before laying down the first trace, you have to find out your preferred manufacturer’s specifications. Some manufacturers provide their specifications on their websites. If they don’t, it is recommended that you reach out to them to avoid your printed circuit board not being functional or meeting expectations.
It is essential to know your manufacturer’s specifications such as trace width, number of board layers, and trace spacing beforehand so that you can design your printed circuit board according to these specifications. This prevents the frustration of having to reroute your entire design at the last minute and working on it for additional hours.
4. Component Placement
How components are placed determines ultimate design success. To properly lay the components that make up your circuit, you have to understand their characteristics. There are specific components that should not be placed close to others. In addition, proper component placement is necessary for convenience.
For example, heat-sensitive electrolytic capacitors must be kept away from heat-generating diodes, resistors, and inductors.
Here’s some good rules of thumb when designing:
- Be mindful of components that have more pins as these will require more space. It’s a common mistake to pack components together, only to realize no space was left for routing traces.
- Keep components placed in the same orientation. Components usually have standard pin numbering to help with this.
- Take each component’s function and its relation to other components into account before placement.
- If components are already procured, then we recommend printing out the layout on paper true to size and see if the components fit.
5. Use 45° Trace Angles
Traces run throughout a printed circuit board and around components. It may seem like a good idea to create 90° angles at corners and bends but this can be a bad idea. To begin with, there’s a high possibility that the outer corner of a 90° trace may be etched narrower than it should be.
The sweet spot is 45°.
45° trance angles make it easier to weave between pads and still produce a beautiful design. Above all, it’s much easier to etch, and your manufacturer will be grateful.
6. Create A Ground Plane
To give all your traces a single reference point for measuring voltage, they must have a common ground. This is especially important in analog circuits. There’s the option of using traces to route to ground. However, you can end up with many different connections on your printed circuit board if you do this. This is because the varying resistance values of the traces can cause different voltage drops.
To avoid creating a nightmare of multiple ground connections and voltage drops, include a dedicated ground plane in your printed circuit board design. The ground plane could be a large layer of copper or, better yet, an entire plane on a multilayer board. With the ground plane in place, all you have to do is connect the components that require grounding to the plane via vias.
7. Use Vias To Channel Heat
Vias provide electrical connectivity between different layers on multilayer printed circuit boards while also having the capability of removing heat. To channel heat away from a component, simply route vias beneath it. These vias will effectively channel away unwanted heat from the component.
Just remember to keep the component’s pins away from the vias.
8. Leave Sufficient Space Between Traces
Earlier we discussed giving your traces as much width as possible. This has to be balanced with the spacing of traces. Insufficient space between traces will cause short-circuiting since traces may unintentionally connect while being manufactured.
9. Utilize The Silk Layer
The silk layer, which comes with printed circuit boards, is useful for labeling and is featured in routing software applications. By using this layer, you can label your components and include information if needed.
Some things to remember:
- Don’t cluster your board with too much text. You don’t need to write down every available piece of information. For example, there’s absolutely no need to label resistor values.
- Try to make your text large enough so that they can be printed legibly.
- Don’t label over exposed copper pads that are to be soldered as the ink may impede the flow of solder, resulting in a bad joint.
10. Leave space between traces and mounting holes
When placing mounting holes for components, designers often forget to leave sufficient space between them. This creates the risk of producing a shock hazard. Always be sure to leave adequate space around your mounting holes to protect them from other nearby components and traces.
The tips laid out above will help guide a successful printed circuit board design. Always remember that planning is crucial so take your time and carefully plan your layout before committing to it. Printed circuit board design is both an art and a science and so patience and time are required to produce an excellent, functional, and beautiful design layout.