A Beginner Learns PCB Routing is Hard

Drawing up the circuit diagram/schematic was a new thing, but I got through it with minimal headaches and was feeling pretty good about using KiCad. After I was done with the first draft, I moved on to route all the connections to be placed on the printed circuit board (PCB). Doing this, I get firsthand experience that wire routing is a hard problem.

The first few connections were easy, but then it got progressively more difficult as I struggled to find a route for the later connections. The center of the board inevitably became a traffic jam and I started having to go around the jam. Every track that go around the outside perimeter of the PCB is a surrender that I couldn’t find a better way.

In addition to the traces going around the outside perimeter, another way to quantify my frustration with my circuit is the number of tracks in the KiCad PCB file. This is a number easily readable in the text format save file.

Fortunately, it doesn’t cost anything to learn by doing, redoing, and repeat.

The first attempt was a hopeless mess and I had to abort before I could connect everything. Here is version 2, where everything is actually connected with almost 200 tracks and multiple traces that go around the perimeter in a last-ditch effort.

LTC-4627JR I2C PCB v2

Version 3 changed the layout of the components in an attempt to make routing simpler. Moved the LEDs to the top, etc. It felt cleaner but is still quite a mess. I managed to avoid long traces that went around the left and right perimeters, but I still needed several at the bottom perimeter. And the track count didn’t improve by much – still just under 200.

PCB Route v3

Version 4 had the same basic layout as version 3 but I’ve learned to recognize a few signs of upcoming problems and could work to avoid them. The result had a further reduction in tracks, almost a 10% cut down to under 180. Plus I needed even fewer perimeter rescue paths.

PCB 4

The English language has the colloquialism “Paint yourself into a corner” and this is a very similar thing – it’s very easy to route yourself into a situation with no way out. I wish I could condense the lessons I learned into a summary here, but so far it’s just a lot of trial-and-error. Try something until I run into an obstacle, then try to figure out how to get out of this mess.

At this point the only words of wisdom I could offer is – dive in and try. It won’t work, but you’ll learn. Try and try again until you get good enough to get to a point where everything is connected, however inelegant it might be, and keep iterating to improve from there.

(The work described in this blog post are publicly available on Github.)

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