Removing burnt solder pads - Page 1
Forum section: electronics / beginners

author: jimmyc_
author_rank: Contributor
timestamp: January 09, 2022, 12:49:28 pm
content: Hello experts!I was recapping on a PSU and found i needed high temps in order to melt the solder. Unfortunately i wasn't able to handle the high temps and gauge the soldering time so I may have burned some solder pads.I have three questions, please help by referring to the attached picture.Each pair (eg green) refers to one electrolytic capacitor.i. Capacitor holes linked to A - These are very hard to melt, how can i get a clear through hole for recapping?ii. Capacitor holes linked to B - These are (comparatively) easier to melt compared to A, again how can i remove solder from the hole for recapping?I've tried with desoldering braid + 450C on a Ksger T12 soldering tool but it's not really getting the results i want. I've also tried with a solder sucker but the hole closes too fast for the solder sucker to do its work.should I get a desoldering gun or consider using ChipQuick SMD1 for low melt temps?iii. Marked C - I've tried to remove this incorrectly and have burnt marks. Is there any way to remove these burnt marks on the PCB?I've tried cleaning with solder flux. Not sure if this is the correct method.Please help me EEV gods!

author: Shock
author_rank: Super Contributor
timestamp: January 09, 2022, 02:30:47 pm
content: The solder sucker should have a heat resistant tip so you can have it right on the joint when it's molten. If it melts in solder it's rubbish.Chip Quik makes it stay molten for longer, you can also buy desoldering pins to unblock holes.In most cases adding a fresh blob of solder to both sides with flux fixes dry solder in the joint. Don't apply pressure with the iron tip. You can also try desoldering braid/wick after adding the fresh solder. If a wire or pin is stuck though your only option may be to poke them out.One other way is reflowing the joint with a little solder on one side and using the sucker on the other side, it can be enough suction to force solder through. Then clean up the excess.Burnt flux can be wiped off with alcohol or flux remover and a cotton bud or old toothbrush and wiping it clean a few times to remove residue. Note that flux sometimes needs to soften up a little.

author: jimmyc_
author_rank: Contributor
timestamp: January 09, 2022, 04:26:24 pm
content: Thank you so much for your advice, @Shock!My solder sucker has a plastic tip and somewhat not very hear resistant. Will look for another.I’ll get the ChipQuik SMD1 and desoldering Pins to work on those holes too.Thanks!

author: Ian.M
author_rank: Super Contributor
timestamp: January 09, 2022, 05:11:00 pm
content: *PREHEAT* !!!ROHS solders typically melt at around 220 deg C. Getting the whole board or at least the surrounding area up to around 100 deg C and *KEEPING* it there will reduce the rate the joints loose heat by 30% to 40%. It will also keep ChipQuik desoldering alloy liquid, giving you as long as you need to clear holes and clean it off pads.Temperature controlled hot air from the component side is probably the best option.

author: jimmyc_
author_rank: Contributor
timestamp: January 10, 2022, 02:50:56 am
content: Thank you @Ian.M! I do have a hot air rework station! I'll try that

author: tooki
author_rank: Super Contributor
timestamp: January 10, 2022, 12:50:09 pm
content: For the solder sucker, buy some silicone tubing that fits over the tip snugly. Cut a piece such that it extends about 3mm beyond the end of the hard plastic tip. With this you can actually be in direct contact with the soldering tip while heating, armed to suck as soon as the joint melts.