I had a difficult day. I was working on a tiny (Flexible Printed Circuit board) FPC that was ripped out of a smart phone. I had just replaced a micro controller chip on the FPC. My end goal was to solve a capacitive sensing problem, but I couldn't seem to even program the damn chip. I checked the programming lines with a scope and verified the waveforms looked ok, but the programming would fail, either immediately or some time part way through the process. Things were getting really flaky and I was irritated because I had lots of real work to do that wasn't even started yet. Initially, it looked like a typical problem whereby the FPC tail is the wrong thickness for the connector. Nope, I checked that. I even ohm'd-out the programming lines to ensure there were no shorts to ground or each other. So, what gives? Finally, I got my laser-focused Sherlock Holmes game face on and looked very carefully at the chip, programming lines, and connector.... hmm.... looks fine except one of my beard hairs fell off and is stuck to some solder flux near the FPC connector. That couldn't possibly screw up the programming, right? WRONG. I removed the hair and problem solved! It seemed that the hair was only partially conducting, and somewhat randomly based on humidity, temp, vibrations, etc...

Of course I always wash the flux off thoroughly when troubleshooting capacitive sensing stuff, but for programming I never really thought it could make a difference. Well, apparently some flux and beard combinations can really conduct current like a MOFO. So much that it can screw up some strong drive programming lines... So lesson learned: wash the damn flux off! No exceptions! And get rid of that beard that's dropping nasty hairs all over the place! Gross!

The next day I came back to work with a clean shave and it felt great! No beard. No flaky programming. Go beardless! And look at my before and after shots - clearly the clean shave is more respectable and makes me look at least 5 years younger (more like 10 don't you think?)