It is a normal human reaction to be wary of an automated technology. We’ve probably all experienced an overflowing coffee machine, a customer service agent in the form of a “chatbot,” a car’s cruise control that won’t cruise, or some other automated tech that’s gone awry. This fear typically stems from a long past incident that has since been corrected. A perfect example of this is using automated trace routing in PCB design CAD systems.
When autorouters were first introduced, they were often difficult to use and delivered questionable results. Because of this, auto-routing was quickly labeled as “black-box magic,” and many designers hesitated to use it. Instead, they would choose to work long hours manually routing their designs. Today’s autorouters, however, are vastly improved from their predecessors and deserve a second chance. As you will see, they can exponentially increase your productivity as a PCB designer.
PCB Autorouting: Old Concerns that Need Updating
First, let’s look at some of the past problems associated with using automated trace routing on a circuit board.
Separate tools with massive setups and price tags
When PCB design autorouters were first introduced, they were primarily third-party tools that were both expensive and difficult to use. Designers had to export their layout into the autorouter, run the routines, and then pull the routed data back into their main design. To further complicate the matter, these routers required many complex configurations to replicate the environment and design rules of the primary PCB CAD system.
Today these autorouters have been refined and are often built directly into the CAD tools being used to lay out the circuit board. Not only has this lowered their costs, but using the native design rules and eliminating the need to export and then import the data has simplified use.
Complex design preparation before going into the router
Another problem that made early PCB autorouters undesirable was preparing the design before sending it into the router. The final results of the router were dependent on this preparation and created extra work and confusion for the layout team. Should escape routing be done, and if so, how much? Which areas of the board should be blocked off with keep-out zones, and which ones should be accessible to the autorouter? And above all, don’t ever forget to lock any manually routed sensitive traces first, or the autorouter would rip them up.
With today’s autorouters being part of the regular CAD system, the designer can quickly test different routing options from within the layout. This convenience saves the enormous amount of time required for sending different layout scenarios to the router to find out which would produce the best results.
Questionable results that required manual cleanup
While the early autorouters could connect traces on the board much faster than a human designer, their execution of the routing often left a lot to be desired. Some traces would take a few laps around the board instead of a more direct route, and others would use multiple vias to detour around traces or vias that easily could have been moved. It was also typical to find superfluous jogs in a routed trace or antennas that could cause signal integrity problems in the design. All of this would require the designer to put in extra time manually cleaning up the routing.
Thankfully, today’s routers have vastly improved algorithms that resolve the majority of these problems. And with the autorouter embedded in the CAD tools, layout designers can now easily preview the results before deciding to save them to their design.
Was it worth it?
With the older autorouters, PCB designers would spend a lot of time preparing their design to autoroute overnight, without knowing what kind of results would greet them in the morning. Too often, the mess that they found waiting for them the next day was not worth the time it would take to clean it up, and they would choose to route the design instead manually. But with the advances in auto-routing technology today, those days are over.
Automated Trace Routing Capabilities for Different Layout Requirements
There are many benefits to using the auto-routing tools within your PCB design CAD system. In addition to all of the improvements made to auto-routing algorithms throughout the years, today’s autorouters have many different capabilities built into them. These features allow you to use the routers for a variety of PCB routing scenarios:
- Escape routing from surface mount pins to vias
- Single line point-to-point routing
- Auto-routing within a defined area or on a specific board layer
- Bus routing of groups such as data or memory lines
- Auto-interactive routing, where the tools automatically add the traces after you specify the direction
- Full batch auto-routing of the circuit board
- Clean-up routing with various options to remove antennas and loops or miter the lines
All of this functionality makes auto-routing a valuable tool in the PCB designer’s toolbox. Additionally, the ability of today’s routers to function in existing design environments using the same design rules and constraints further enhances their value. Using the automated trace routing features in your CAD tools can help you increase your PCB design efficiency, improve the design quality, and get the job done sooner.
For More Help with PCB Design
Autorouting is just one of the design methodologies available that can help you to increase both the efficiency and quality of your PCB designs. Many other techniques can also help, including schematic capture tips, part selection, component placement, and design for manufacturability recommendations. The key to utilizing these tools is to partner with an experienced PCB contract manufacturer.
At VSE, we have well over 30 years in the circuit board design and manufacturing industry, and we can help you with all your design challenges. We’re ready to partner with you to answer design questions, help to navigate today’s turbulent component supply chain, or provide complete PCB layout services.
