by Kerstin
October 21, 2022
PCB knowledge
(0)
05 mins

What is PCB routing and how does circuit board routing work

Routing the traces presents a problem when planning a PCB layout. Which path is ideal to follow to complete the connection? The answer to this question is unclear because numerous traces can exist on a PCB board and different issues sometimes appear. However, you must choose an ideal path to finish your creation. Examining various trace conditions can help determine optimal PCB routing strategies and optimize board layouts.

Let’s have a look at all the other aspects designers must know before PCB routing.

What is PCB routing?

PCB routing places the pads, holes, and traces on a printed circuit board (PCB).

Routing is done with a router, also known as an auto-router. This machine has two heads:

One is a milling tool;
The other is a drill head.

The router can mill away the copper and drill holes in the PCB.

A computer program tells the router where to place components by creating an image file that describes the router where to mill or drill. The image file may be called a netlist or GERBER file.

The image file will contain multiple layers, including traces, pads, vias, and other elements required on your printed circuit board (PCB).

What is PCB routing trace?

PCB routing trace is a layer in a PCB design that provides a path for signals to follow, usually from the component side to the solder side.

The PCB routing trace layer contains traces that are routed between components on one side of the board and pads on the other side of the board.

A PCB’s traces may contain stringent design specifications that maintain signal integrity while routing. Even though traces may have unique routing needs, you can set up and adhere to design rules for your traces with the aid of today’s more sophisticated PCB routing approaches and capabilities.

How do you route a PCB?

PCB routing is an essential step in the PCB design process. It involves placing tracks on the PCB and assigning them to different layers. To perform this task, designers can use free PCB design software like PADS Layout.

Check out our post on PCB layout software for more information about PCB design software.

PCB routing involves the following steps:

Draw the circuit diagram and place it on the top level of the PCB.
Place all components so they don’t interfere with each other, and their leads don’t cross over each other.
Plan where each track will go and how many vias need drilling. Use a pencil for this purpose so that you can erase it later if required.
After finalizing the circuit layout, export it as a Gerber file from the PCB software and open it in PADS Layout. The Gerber file contains information about which layers should be routed (top, bottom, etc.) and which tracks need to be connected via vias on different board layers.

Some methods of PCB routing

Here are some main methods of PCB routing:

Maze routing

Maze Routing (also known as min-cut) is a method that tries to minimize the length of the wire by taking ‘shortcuts’. Maze routing is easy to implement but can result in suboptimal routes and might not work well on complex PCBs.

X-Y routing

X-Y routing works by considering the layers of copper on each net side and their cost when sending signals from one side to another. Each layer’s cost depends on its thickness and if there are other traces above or below.

Rules for PCB routing

The following are some general rules for PCB routing:

Use layers with no copper when possible.
Use wide traces whenever possible.
Keep traces short and straight where possible.
Avoid crossing traces, but if you must cross one trace over another, keep them as close together as possible without overlapping.

Tools for PCB routing

There are several tools available for routing PCBs. Here are some of the most common:

Allegro PCB editor: This free software allows users to create designs from scratch or import ones from other sources. It has various features, such as auto-routing and importing Gerber files.

PSpice: This software primarily serves for electronics simulation, but it also has a PCB routing feature that can be useful in certain situations. It allows users to model their designs ahead of time, so they know what will happen when they start building them.

OrCAD capture: This tool was designed specifically for PCB design, so it’s very easy to use and has many features built right in. One nice thing about OrCAD Capture is that it works with both traditional printing styles (where copper is etched off) and newer ones where ink is applied directly onto the board using screen printing techniques (this method doesn’t require etching).

Considerations while doing PCB routing

Here are some things to consider when doing PCB routing:

1) Consider the number of layers in the design.

2) Consider the size of the PCB board.

3) Consider the amount of space available for components.

4) Consider what kind of circuit designing.

Challenges designers face during PCB routing

During routing, designers face several challenges, including:

Complexity of design: There are many types of PCBs, meaning that every type has its rules and routing requirements. On top of this, the number of layers can vary from one board to another. The more complex a design is, the more challenging it will be for you to route it accurately.

PCB material limitations: Most PCBs are made up of FR4 or FR6 materials, which have certain limitations regarding routing speed and power consumption. If the design has high power consumption or high-speed requirements, then using these materials may not be feasible for your project.

Multiple tools required for successful routing: You need to use several tools during the process — like CAM systems and routers — which means that there are multiple points where errors could occur during the process (for example, if there’s a bug in one tool). This increases both time spent on fixing issues as well as cost.

Conclusion

So that’s a quick overview of PCB routing. By now, you may be able to figure out how to route some traces on an actual PCB. Of course, there’s more to learn in PCBs and electronics! IBE has prepared everything for you.