How to wipe "fresh" solder paste from PCB - Page 1
Forum section: electronics / general

author: olkipukki
author_rank: Frequent Contributor
timestamp: December 07, 2020, 10:54:43 pm
content: Let's assume you messed up with a manual printer and stencil alignments, so a solder paste need to be reapplied again on PCB board.How and what do you use to wipe a paste and keep PCB board clean?

author: jmelson
author_rank: Super Contributor
timestamp: December 08, 2020, 04:02:27 am
content: I've done it with denatured alcohol and a paper towel. It takes a LOT of wiping, one quick wipe does NOT remove all the paste and flux.Jon

author: SMTech
author_rank: Frequent Contributor
timestamp: December 08, 2020, 11:27:49 am
content: Quote from: jmelson on December 08, 2020, 04:02:27 amPlus you're going to end up with paste in awkward pits between pads, and in any vias/holes and routing, most of it will probably do no harm depends on the application and the desired finish I guess. If you have a way of drying the PCB thoroughly and an ultrasonic big enough, that would work quite well with the use of a flux saponifier.

author: olkipukki
author_rank: Frequent Contributor
timestamp: December 08, 2020, 11:56:15 am
content: Quote from: jmelson on December 08, 2020, 04:02:27 amDo you clean your boards?Wouldn't a paper leave some residues?

author: olkipukki
author_rank: Frequent Contributor
timestamp: December 08, 2020, 11:58:54 am
content: Quote from: SMTech on December 08, 2020, 11:27:49 amIs ultrasonic cleaner only proper option left?What about chemicals - can be used with stencil clean or completely different?Another concern - waste process a bit complicated, isn't'?

author: SMTech
author_rank: Frequent Contributor
timestamp: December 08, 2020, 01:02:50 pm
content: I think waste issues will depend on your scale. If you're building stuff in your garage and wiping the occasional board that a whole different ball game to if you have a massive line and a washing system that cleans your stencils and misprints, at that point even the water from your compressor could be an issue if its not oil free. Using flux cleaning saponifiers and wipes might also work, stencil cleaner does too of course. A stencil wipe should be lint free and thus might be better than a paper towel (really depends on the wipe and the towel, frankly I've seen some where the roles seem reversed).Personally I try and take enough care that misprints are rare and for minor issues its easier to mark the board for later rework than it is to clean it off, plus in a lot of cases you can get away with quite a lot.

author: SMdude
author_rank: Frequent Contributor
timestamp: December 09, 2020, 08:16:04 am
content: I use "brake clean" or a similar parts cleaning solvent. Cleans up boards and stencils really easily.And I just use a paper towel to clean with and then keep the paper towels, at some point I will burn them off in a drum and collect the solder from the bottom so it doesn't end up in the ground at the tip or wherever it would end up.And if I clean everything in a tub, I collect the solvent afterwards in a bottle, the solder paste settles to the bottom, so the solvent can then be used again.

author: TIOUK
author_rank: Contributor
timestamp: December 10, 2020, 12:48:49 am
content: IPA using those non woven fabric wipes that actually look like woven cloth, ours are orange, come on big rolls for a couple of quid.The paste goes into the holes in the cloth so you can wipe it off, then rinse in a seal-able plastic tub (like the sandwich boxes from you local supermarket with the silicone gasket) with a cm of IPA in the bottom.You can keep the plastic container sealed and the IPA doesn't evaporate.If you use paper towels it just smears it around the board.

author: S. Petrukhin
author_rank: Super Contributor
timestamp: December 12, 2020, 04:41:10 am
content: Quote from: olkipukki on December 07, 2020, 10:54:43 pmYou can heat the PCB until it melts and blow off the solder with compressed air like HASL (only carefully) or assemble with a braid.But wiping it with a napkin soaked in alcohol is not a problem for me. I do not think that some of these small balls that got into the holes or remained on the surface on the soldering mask will cause harm. In the holes, they will melt and improve metallization, on the mask they will not stick after melting and will be washed off or attracted to the nearest pad. Only BGA is dangerous.

author: Rat_Patrol
author_rank: Frequent Contributor
timestamp: December 15, 2020, 09:38:03 pm
content: I just drop it into the ultrasonic cleaner