How to ruin your afternoon

After soldering and assembling my 7 segment display modules, I saw a very unexpected behavior in most of the modules. Some displays worked just fine, but some would flip – or half-flip – multiple segments at once.

After much testing, I saw that the modules with the green PCBs worked, but the blue ones did not. I remembered that I fixed a missing wire, but other than that?

I compared versions in my CAD system, but the only thing I changed was the drill diameter for the display pins. Nothing more. How would that… ?

Wait a minute. Uh-oh. Taking a larger drill did increase the pad diameter which now touches a trace that was layed too close to the pad to begin with. Why did I not take the DRC check seriously.

Anyway. Here I sit, scratching through the traces on 20-some PCBs. Sigh!

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