Laying out a printed circuit board can be time consuming. Every layout has to balance your board’s intended purpose with efficient routing and ease of manufacturing. For many projects, printed circuit board layout can feel like art as much as engineering.
The good news is that with practice, you’ll quickly become proficient in printed circuit board layout. In this guide, we’ll explain the fundamentals of laying out printed circuit boards and highlight some of the tricks you can use to master the process.
Printed Circuit Board Size and Shape
The best place to start when laying out a board is to determine what size you need. A larger board offers more room to place components, but it also opens the possibility of adding more components and more functionality. A small board might require you to sandwich all your components together, but it can be easier to work with in that the total number of components you can add is limited.
The shape of the board is important, too. While most printed circuit boards are square, they can also be rectangular, triangular or circular. Switching to a different board shape can give you a new perspective on your layout. For example, it can be helpful to experiment with laying out components on a circular board if you’re having trouble making them fit together on a rectangular board.
Ultimately, most printed circuit boards need to fit into a specific space or housing inside a larger device. This can dictate the size and shape of your board to a large extent, and in some cases you might have to use a smaller board than you would prefer. Thankfully, there are some adjustments you can make to your layout to ensure that all your components fit.
If your board is tight on space, printed circuit boards with multiple layers can help. Two-layer printed circuit boards can have components on both surfaces, or components on one surface and a grounding layer on the other. Compared to a one-layer board, two-layer boards offer up to twice the amount of usable space for laying out components.
However, connecting all your components on a double-layered board can still be tricky. Components and traces take up a lot of real estate on the surfaces of your boards. The more components you add, the more difficult it becomes to lay out traces without them overlapping each other.
To get around this problem, consider using a four-layer printed circuit board instead of a two-layer printed circuit board. In a four-layer board, the two outer layers hold components while the two inner layers serve as conductive planes. You can easily route traces between components on either surface using the two inner layers, which frees up space on the outer layers for additional components.
Traces are the small wires that connect components across your printed circuit board. They carry power and electrical signals between components, so they’re absolutely essential to the proper functioning of your board.
Placing traces can be one of the most challenging parts of laying out a printed circuit board. Ideally, your traces should travel the shortest distance possible between components. The shorter the distance that the electric current needs to travel across your board, the more efficient the signal transfer will be.
On most boards, it’s impossible for all the traces to travel in straight lines between components. We recommend that you prioritize layout for traces connecting components that need to process signals from one another quickly. For all other traces, use 45-degree turns instead of 90-degree turns to shorten the electrical path between components.
You will also need to pay attention to the width of your traces. Using the narrowest possible traces is appealing because it saves space on the surface of your board. However, narrow traces can only handle a limited amount of current. If you use traces that are too narrow for the current that they’re carrying, your board can overheat. We recommend using this trace width calculator to calculate how wide the traces on your board needs to be.
Bringing Your Layout to Life
We recommend using a dedicated design software to help with the printed circuit board layout process. That way, you can build and modify a digital schematic to get the layout just right before diving into the full design of your board.
Don’t be afraid to try out your software’s auto-routing feature if it has one. Auto-routing can make the process of mapping traces both faster and easier. However, it won’t work for more complex designs. If that occurs, you will need to take the reins and manually route the traces on your printed circuit board.
Ultimately, laying out a printed circuit board requires some trial and error. The process becomes easier with practice, and these tips will help you get a head start on your next design.