Found a cracked solder joint on a flight control computer last Tuesday

I was doing a routine bench test on a flight control computer from a King Air that came in for an intermittent fault. The pilot said the autopilot would drop out randomly but only in turbulence. After about an hour of signal tracing I noticed the voltage on one pin would flicker when I tapped the board near the edge connector. I put it under the microscope and found a hairline crack right where a resistor lead met the solder pad. Reflowed it with fresh solder and the flicker disappeared completely. The computer passed all its functional checks after that. Has anyone else run into those cold joint fractures on older Rockwell Collins boards?

3 comments

3 Comments

wilson.kelly22d ago

Did they actually reball those old boards or just flow a ton of solder over the fracture? I've seen that trick hide the real problem for months before it comes back worse.

derek65622d ago

Man that brings back memories of a similar issue I had on an old Collins radio stack... spent two days chasing a ghost only to find the same kind of crack right by the connector pins.

andrew_rodriguez22d ago

Nah @wilson.kelly, that trick never works long term, you're spot on. Seen guys slop solder over a crack like that and call it a day, but thermal cycles always find the weak spot again. On those old Collins units the board material gets brittle with age too, so the crack just spreads under the new solder eventually. Makes me wonder if the OP's issue is gonna come back in a few months even after the repair.