A quality inspector's offhand remark about solder joints made me redo 14 harnesses

Last month we had this FAA guy walking the floor for a routine audit. He stopped at my bench, looked at a connector I just finished, and said 'you know that shiny solder means cold joint, right?'. I had been doing it the same way for 6 years, always chased that mirror finish. Turns out he was right, the grain structure was wrong, we had two intermittent failures that traced back to my work. I reflowed all 14 harnesses over the weekend and tested them on the thermal cycler. Now I leave the iron on the joint 2 seconds longer and let it cool slower, no more polish. Has anyone else had to unlearn a habit that looked right but was actually causing issues?

2 comments

2 Comments

wren_smith4423d ago

So how did you figure out the grain structure was the problem, x-rays or just the failures?

piper17522d ago

Started with the failures honestly, but only after a few parts kept cracking in the same spot did I dig deeper. The x-rays just confirmed what the microscope was already showing, those grains were way too coarse for the stress we were putting on them. Once I saw the pattern on the fracture surface, it was pretty obvious it wasn't a random flaw but a structural issue. After that we switched to a finer grain alloy and the problem just disappeared.