Material for scrubbing Cu-clad boards

It has been quite a while, but in the old days I used Seno Polyblock. That is (or was) a kind of big (matchbox sized) crayon eraser, specially made to clean Cu plating.

The acid is going to eat it off of ALL the unmasked areas and a little tarnish wont stop it. I think abrasive scrubbing was overkill this whole time.

I use 400grit or finer sandpaper lightly and I don't get deep grooves. I suppose for RF you would want a very light abrasive so as to keep the cooper uniform. This assumes the board itself already has uniform copper distribution. I doubt that most general purpose boards have precision distribution .

Acid ? I use Polyblock to remove the photolayer. That is after the etching process :-)

Scotchbrite, with soapy water. When scotchbrite was first invented, it was a very expensive industrial product and one of the first markets was PCB fabbers. Years later it became a household product.

Use the green kind, the more agressive stuff, not the gentle version.

John

There used to be a liquid cleaner for "Revere Ware", the copper

-bottom cooking pots. Use with a plastic or nylon scrubbing pad. ...Jim Thompson

Tarn-X

That should also get rid of oils with a little aggitation.

I use a green nylon scrubbing pad (3M or generic equivalent) with either some Comet household scrubbing powder (for fast cutting) or a squirt of Gojo hand cleaner (an orange-scented gel which contains some pumice).

On the last board I did, I scrubbed down the board in this way, rinsed well, and then dipped it into the PC-board etchant solution for a few seconds and then rinsed again. The brief dip in the etchant left the copper surface with a very uniform matte appearance - I think it evened out the larger scratches left by the pumice/cleanser.

The pattern ironed on quite well and etched nicely.

But FeCl3 has a hard time eating through grease and finger smudges. I always have a stack of 12"x12" copper-clads in stock and some of them go through a lot of handling and shuffling before it's their turn to be used. And since it's best to remove any tarnish anyway before soldering, scrubbing followed by a thorough rinsing in running water ensures a smooth process.

I was really talking about pre-etch cleaning.

I'm with John... I use a Scotchbrite pad with soap, too.

Tom P.

Jim Thompson wrote in news: snipped-for-privacy@4ax.com:

Tarn-X works well,or Barkeeper's Friend.

steelwool leaves tiny bits of itself behind.

I suppose not. I'm not really concerned about that, but it's nice to know that individual particles of the scouring powder are not hard enough to score deeply into the copper. What I didn't mention earlier was that I keep board and powder wet while scrubbing. A level teaspoonful of powder is more than enough to get a palm-sized board sparkling clean without any visible nicks and scratches, and it takes under a minute of mild scrubbing unless the board is heavily tarnished.

I have no reason to doubt that Scotchbrite works well, but it's not available where I am.

I tried using the green pad too, but I really prefer scrubbing with my fingers. Of course, I wouldn't recommend it for mass production!

I sometimes do the pre-etch (brief dipping) too, but somehow I don't have the patience to make it a regular practice. No logic here as I'm normally a very patient type.

Where's that? In supermarkets here, we have several brands of kitchen sponges that have generic Scotchbrite on one side. They work great to clean up pc boards.

John

Kleen King worked like a champ for me. Art

NEVR-DULL tarnish removal wadding will aid in getting the stuff scrubbed off too. Also a very good pre-prep for the HASL to follow.