(2024-03-19, 10:53 PM)Adrian Wrote: I just checked the RJ45 connector on the latest batch. It's going to be hard (impossible?) to resolder the mechanical pads just with a soldering iron. Heating the board from the bottom is probably your best chance.
I've made a note to extend the mechanical pads from under the part so that they can be more easily reworked.
Yup. I have both a heated plate as well as a hot air station - I think between the two I can make it work. Worth a shot anyway.
Below are a couple of pics, as close as I could get with my cell phone. Unfortunately the downlight for my microscope was not working, so I couldn't get better close-ups. On the rear, in case it isn't clear, the two most-inboard contacts are completely detached from the solder pad, while the next contact in seams to be partially detached but is still holding on a bit. The rest of the contacts outboard of this appear to still be attached. Both of the large pads underneath the jack have separated from the PCB. It does not appear that any pads or traces have been torn or lifted from the PCB.
A friend with more experience than me (he performed component level repair on audio gear as his job for many years) took a look at the pics and his first thought was a poor bond due to dirty/oily surfaces, along with possibly not enough heat in the joints.
For a contamination hypothesis, he pointed at the rear contacts, where they have come away from their pads. "Those contacts are tiny - any force sufficient to yank a component like this off of a well soldered board would almost certainly have ripped those contacts completely."
For the insufficient heat hypothesis, he pointed at the picture of the large contact pad that has two cylindrical columns rising from the PCB. These came from the solder squishing up through holes in the metal mounting part of the jack. He said that on a properly heated contact, the solder should have squished up through the hole and then formed a bit of a mushroom cap on top. But the top of those columns did not appear jagged as if the mushroom cap was torn off - they looked smooth - which led him to think that the solder cooled down right as it was being squished through the holes, and formed a column shape that did not spread out on top.
All he saw was the pics, but his thought was that it was a combo of not enough heat and some contaminated surfaces that likely caused a poor bond. It sounded reasonable enough to me