I’m trying to solder on the flex cable for a PicoFly. I’ve added some solder to the bottom two points that are touching the metal surrounding the CPU. However, I seem to only be making a bigger and bigger ball of solder when trying to melt it. I’ve upped the temperature on my iron but that doesn’t seem to be doing anything. What am I doing wrong?
Flux is important. If you aren’t using flux core solder, that could be part of the problem. Flux cleans the surface and it’s easier for the solder to stick. (Flux also comes separately and it a wide variety of formulations.)
If flux isn’t the issue, then it absolutely is heat. I tried to Google for a picture of the “metal surrounding the CPU”, but I couldn’t find one. From your description, it sounds like that metal is still sinking too much heat away which also wouldn’t allow solder to flow.
Soldering to larger metal pieces is always a challenge. You likely need a lot more heat applied for the shortest time possible. Another option is to heat up the entire board with a hot air gun first, but I suspect that is not an option for you.
Big soldering tips can be used to flow as much heat into the part as fast as possible before the heat gets a chance to spread out.
(A picture of your problem would be a nice-to-have. I am not familiar with your exact components, but I solder things quite a bit.)
The metal shield maybe? There’s probably a word for it but I mean the bit the white arrow is pointing. The board in this picture isn’t the same board, but I’m not able to grab a picture of the board in question at the moment. I can reply with a picture of the board & solder once I’m able to grab one. I am using flux, I just hadn’t mentioned it. I did try heating it up with a hot air gun since I have a two in one rework station but that didn’t seem to do the trick. I’m guessing I wasn’t applying sufficient heat for long enough.
Thanks for the pic! That helps visualize the situation for me. Unfortunately, I can’t be much more of a help.
Getting a sense of how hot to get everything with air is a dark art. I can only say that it’s needs to be below the solder melting point and too hot to touch any part of the component.
On top of the shield sinking heat, the board is likely using silver-based solder, which also requires high heat. (Flux would have a dual role in cleaning the area and also flowing some heat around the solder joint a hair more efficiently.)
If it were my equipment, I would YOLO the iron temps and experiment with contact timing to get the factory solder melted enough to flow in some lead/tin solder. My tolerance for damaging my own stuff is super high though. (Brute-forcing as much heat on a small area before it gets the chance to dissipate is the logic here.)
Practice makes perfect. If you have an old wifi/Bluetooth device you can risk destroying, it might have shields you can practice removing or soldering around. (Noise sensitive audio components are something else that might use shields as well.)