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The Shaughnessy Report: Planning Your Best Route

Designers don’t like autorouters, period. In my 26 years of covering PCB design and EDA tools, I’ve met about 25 designers who admit to using autorouters regularly. Two of these, Barry Olney and Stephen Chavez, have articles in this issue. If experts like these use routers, why haven’t you tried one?

I’ve heard dozens of reasons why designers don’t like routers, but here’s the top five:

1. “I just can’t get autorouters to do what I want them to do.”
2. “In the time it takes to set up an autorouter properly, I can manually route the board.”
3. “Clean-up takes longer than actual routing.”
4. “I just don’t trust them.”
5. “Autorouters make your design look like [#&$%].” 

That last one might be Number 1. Columnist Kelly Dack says that upon seeing certain boards, he has been known to exclaim, “Ewww, that board was autorouted.” 

Even EDA companies will admit that autorouters used to be clunky and inefficient. But a lot has happened since Cooper & Chyan Technology launched Specctra, the first gridless router, in 1989. It was the first shape-based autorouter, and it revolutionized the autorouter segment. 

Cadence Design Systems acquired CCT in 1997 and integrated the Specctra gridless autorouter into its Allegro tool. Other software companies soon followed suit with their own gridless routers, and a lot of industry watchers thought the day of the autorouter had arrived. 

Autorouters did become popular—among IC designers. But IC designers really don’t have a choice. Manually routing billions of transistors on an ARM processor would take years; a PCB designer can manually route even a complex board in a matter of hours or days. 

Today, the “Big Three” EDA companies all have PCB autorouting technology that can run rings around the ones of a few decades ago. They all use some form of AI. They allow users to determine the level of automation they’re comfortable with, and they boast completion rates much closer to 100%. 

We are seeing baby steps in autorouter adoption. The flexibility of today’s autorouters has ushered in a sort of hybrid style, with designers doing much of their manual routing within the autorouter environment. I have noticed that younger PCB designers seem more open to autorouting than their senior designer co-workers. With designs becoming more complex all the time, some designers may have to try autorouting just to stay on schedule.  

Are autorouters finally going to get their day in the sun? Is your best route through manual or autorouting, or a hybrid mixture of the two? 

This month in Design007 Magazine, we asked our expert contributors to weigh in on manual routing and autorouting, and to share some of their best routing strategies for both. Our contributors include Zuken’s Andy Buja, Cadence’s Patrick Davis, Siemens’ Stephen Chavez, and columnists John Watson, Barry Olney, and Kelly Dack. We also have a column by Matt Stevenson and a paper by Maria Cuesta Martin that was presented at the Pan-European Electronics Design Conference in Austria this year.

I’m done with work travel for a few months. I feel a vacation coming on. See you next month.

This column originally appeared in the June 2025 issue of Design007 Magazine.