PCB Rework and Repair Guide [pdf]
intertronics.co.uk56 points by varjag 2 days ago
56 points by varjag 2 days ago
Almost 30 years old. Old good times without BGAs and modern barely visible components. While some basics are still applicable the modern problems are not covered at all.
Provided you have good eyesight and steady hands, I've mostly found what happens as you get smaller is:
- Heating becomes easier. There's no large sinks to take the heat away. It's also easier to overheat things.
- You need finer tweezers, and don't drop them because if you do the tips will bend.
- The solder's surface tension does more of the work. It feels a lot more like sticking together things with tiny droplets of glue. Having the correct amount of solder in the right place is critical.
- Solder and flux become two separate things you have to care about individually
- It is easier to burn yourself
- learning how to brace your hand against something in a way that gives you very fine control. One reason soldering with an iron can be difficult is because your hand is so far away from the tip, like trying to write with a pen held by the end.
I don't think that modern boards are really repairable at all beyond component replacement- 4+ layer stackups being the big reason. If there's a way to do anything to those boards besides total replacement I'd be super interested to know.
The techniques here are also way beyond basics I think- like, you look at most guides for repair and it's "idk just solder some bodge wires on there, here's what a good joint should look like"
Andrew Zonenberg posted a Twitter thread a year or two ago where he fixed a missing PCB trace some layers down a PCB, with a stereo microscope, precision mill and very steady hands.
Edit: here's the thread. It's a 6 layer PCB with a short on L5 that needs to be fixed from the L1 side.
It's great for working on vintage equipment, stuff that might need (and warrant) that kind of repair. Less so if you run a cell phone repair shop.
Missing: how to solder a wire to the thermal pad on the bottom side of an IC. Assume there are components on the back side.
Beautiful illustrations!
Watch the PACE videos as well, they’re on YouTube and they also cover how to remove conformal coating and using different tools.