Any tips on polishing this off these pcb's? - Page 1
Forum section: electronics / repair

author: alank2
author_rank: Super Contributor
timestamp: May 16, 2016, 05:18:18 pm
content: I ordered some of these and they ended up with a rough finish on the surface.Any ideas on how I might be able to polish these so they are smoother without taking off the silkscreen?Maybe some part of the cleaning process didn't go to plan?

author: tautech
author_rank: Super Contributor
timestamp: May 16, 2016, 08:42:31 pm
content: Looks like a salty residue, have your tried warm water and a soft brush?

author: edy
author_rank: Super Contributor
timestamp: May 16, 2016, 11:52:12 pm
content: Is 99% isopropanol swab not a common way to clean up electronics?

author: alank2
author_rank: Super Contributor
timestamp: May 17, 2016, 01:50:18 am
content: I have tried both IPA and warm water...

author: tautech
author_rank: Super Contributor
timestamp: May 17, 2016, 02:01:05 am
content: Quote from: alank2 on May 17, 2016, 01:50:18 amDetergents?Thinking more.....are the pads plated?Could it be a plating bath contamination residue?

author: alank2
author_rank: Super Contributor
timestamp: May 17, 2016, 01:46:30 pm
content: It is just a standard HASL. I tried an eraser on some of it and it didn't touch it at all. I was hoping for some sort of polishing idea.

author: Jeroen3
author_rank: Super Contributor
timestamp: May 17, 2016, 02:08:49 pm
content: Quote from: edy on May 16, 2016, 11:52:12 pmNo. If you have a water soluble flux or paste you'll be scrubbing life or death with IPA, while a small splash of hot water removes it almost immediately.I once caught my coworker cleaning coffee rings off his table using IPA, it didn't do anything. One wipe with demineralized water and it was gone like in the TV ads. If only you could see his face.

author: Ian.M
author_rank: Super Contributor
timestamp: May 17, 2016, 02:24:23 pm
content: It depends. If the defect is residual plating or etching bath salts under the soldermask, due to a board washing failure, you are FUBARed, and your only option is to reject the board. If its on top of the soldermask, try a hot very mild detergent solution and a 'pink' scourer pad (the type that's safe for non-stick pans), but the board must then be dried for at least 24H before soldering. If that doesn't remove it, try IPA and even Naptha, but don't get your hopes up!

author: alank2
author_rank: Super Contributor
timestamp: May 17, 2016, 02:35:21 pm
content: Quote from: Ian.M on May 17, 2016, 02:24:23 pmI think you are probably right Ian, nothing I've tried seems to touch it.

author: Ian.M
author_rank: Super Contributor
timestamp: May 17, 2016, 03:21:23 pm
content: As a diagnostic, try scrubbing an area without any silkscreen or exposed pads heavily with metal polish and a Q-tip. If its under the soldermask, that will do nothing. If its a problem with, or on, the soldermask surface, you should see some improvement, but whether or not its practical to polish out the defect without eradicating the silkscreen is another matter . . .I suspect you'll end up rejecting the board(s).

author: alank2
author_rank: Super Contributor
timestamp: May 17, 2016, 05:21:24 pm
content: Well. I took some Flitz to it and it dulled the shiny away. I can't say that it removed the issue, but it is hard to tell now. I think it is below the surface too far so for a visible type application it will be an issue. Just as a quesiton, for a board no one is going to see, do you think there could be a long term corrosion effect from it not being cleaned well enough?

author: Ian.M
author_rank: Super Contributor
timestamp: May 17, 2016, 05:38:30 pm
content: If its contamination under the solder mask, its potentially a major reliability issue, more so at higher voltages or if its to be used outdoors or in high humidity. If however its a surface defect of the solder mask, it should be fine unless you are working with very low currents or very high voltages. Some testing with a Megger before you start assembly would be a good idea.