How to remove solder from PCB holes with tiny pads + Nippon ChemiCon Failed caps - Page 1
Forum section: electronics / projects

author: hgg
author_rank: Frequent Contributor
timestamp: May 26, 2015, 08:44:10 am
content: Hi everybody,In the process of upgrading the fan on my graphics card, I discovered this:3 electrolytic capacitors had failed as usual...Interestingly enough they were Nippon Chemi-Con 680uF 16V KZG series.They measured 100uF with an ESR of 2.0 Ohm @ 100Khz.The graphics card was still working fine though.Its a Sapphire ATI HD 3850 and I am now wondering if these were genuineNippon Chemi-Con caps.I have replaced them with Nippon Chemi-Con KZN series with a little bitlower ripple current.Anyway, I am writing this to ask you what is the best way to remove the solderfrom PCB holes with tiny pads like in this graphics card ?I've tried putting more solder and then using a solder suction tool but nothing.I've tried solder wick and nothing again! I simply could not remove the solderfrom those tiny solder pads/holes. I gave up and soldered them on the backof the board laying on their back and glued them with a bit of hot glue.So, what do you think is the best way to clean these pads?Thank you.George.

author: wraper
author_rank: Unknown
timestamp: May 26, 2015, 09:03:42 am
content: KZG are plagued series, so nothing extraordinary. You can use some needle (for example from syringe) to make a hole while heating the pad on opposite side. Or just push the leads of the capacitor into holes while heating with soldering iron without cleaning them at all.Quote from: hgg on May 26, 2015, 08:44:10 amat what temperature this card does work do you think? PCB is even a bit discolored in the place where you applied the got glue.

author: djQUAN
author_rank: Frequent Contributor
timestamp: May 26, 2015, 09:05:04 am
content: With a multilayer board having lots of copper like that, it gets tricky but I have successfully done it using a solder station and a sucker.Hold the PCB vertically. Crank the heat up to about 400-420degC and heat one side for a few seconds adding fresh solder on the other side of the board. While the iron is still on the side with more copper (ground/power plane etc) use the sucker to remove the solder from the other side. Just lift the iron slightly just before sucking so the air can enter the hole and clean it.

author: hgg
author_rank: Frequent Contributor
timestamp: May 26, 2015, 09:16:44 am
content: Indeed blowing the solder out or sucking it from the opposite side would have been easier.I didn't think of that...QuoteSo, maybe its always better to check the series and not the brand.QuoteI had the same thought but the card does not reach high temperatures evenat full load. GPU works at 45-52 degrees Celsius.I will check again though, just in case...

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: May 26, 2015, 09:32:14 am
content: After removing the component lead, fill the hole with leaded solder, then while still molten, tap the board sharply on the edge of the bench - the solder will fly out leaving the hole clear.

author: wraper
author_rank: Unknown
timestamp: May 26, 2015, 09:36:07 am
content: Quote from: hgg on May 26, 2015, 09:16:44 amThis is VRM, not GPU area. Without any heatsink I guess.

author: Macbeth
author_rank: Super Contributor
timestamp: May 26, 2015, 09:43:10 am
content: Quote from: mikeselectricstuff on May 26, 2015, 09:32:14 amThis works really well, because as everyone knows lead is really heavy, I mean like a ton of lead vs a ton of feathers heavy

author: firewalker
author_rank: Super Contributor
timestamp: May 26, 2015, 09:58:46 am
content: I am flooding the hole with leaded solder (or eco-solder with liquid flux) and use a manual sucker to the opposite side.Alexander.

author: hgg
author_rank: Frequent Contributor
timestamp: May 26, 2015, 11:11:08 am
content: QuoteHeatsink on everything including ram and VRM.Guys thank you for all your suggestions!I took some old controller boards with 0.7mm or smaller diameter pads and tried all the suggestionsto see what worked best.By far the easiest, cleanest, safest and more effective solution was to use a syringe.You hold the needle on top of the pad almost vertically and while applying heat with the solderingiron you quickly blow air with the syringe. It worked everytime with perfect results!A combination ofDeathwish'sandwraper'smethod.I've tried holding the board vertically and using the sucker from the back of the board, but it wasa bit cumbersome to align the tool and the soldering iron. It worked but not all the times and itwas more difficult for components that were in the middle of the board.I've also tried Mike's suggestion that seemed intuitive but it worked some times and if the pad holewas small it was more difficult. Maybe surface tension was greater than the acceleration producedby the hit. Also I am not sure if that method does not damage some solder joints, especially surfacemount ones.The syringe needle blower worked like a charm!Thanks.(Maybe comparing all the different methods would be a good YouTube tutorial!)