PCB's

Has any one found an easy way to remove the clay residue that remains on PCB's after soaking the paper off when making iron on resist patterns using the laser printer /photo paper method? The only way I have found is to gently abrade the residue off with a "Scotchbrite" (or similar ) abrasive pad and water. But in doing this I'm always afraid of damaging the resist pattern, especially on a board with SMD traces.

John

Have you tried Citric acid?

- Nick

It's not unusual to polish up a board with a garryflex block to get it ready for soldering, should remove any paper residue OK and a bit gentler than scotchbright

Neil.

Hi John,

I use isopropyl alcohol on a piece of tissue, it doesn't remove the laser toner if you don't rub too hard.

Keith

All

Thanks for the suggestions, but I have tried, isopropyl, acetic and citric acids and they don't touch the residue. Maybe it's the particular brand of paper I'm using. For the two I did last week I used a dry VERY well worn "scotchbrite" pad and gently rubbed the board just until all the residue was removed from the copper areas. There is still a fair amount left on the traces but I don't think that should be a problem. I haven't etched them yet so we'll see.

John

Edited By John Purdy on 18/01/2017 00:11:24

It depends on what medium you are using to print on is it a special toner transfer paper? You could try just brushing with a toothbrush in hot water. I have used the blue "Press n Peel" in the past and had no problems with residue but now use photo etching.

Russell

I quite often leave some clay residue on the toner traces. Providing the copper is clean and the lines are nice and crisp it doesn't seem to affect the etching process. After etching it will all clean off with cellulose thinner, acetone or something similar.

Keith.

Ah!

If you haven't etched yet, and they aren't stuck to the clear areas, just leave them alone.

Neil

I've etched the boards and the clay on the traces caused no problems. Maybe it just adds an extra layer of resist. Over the years I have made probably 50+ boards, On the first ones when I was a young teenager the resist pattern was applied with a paint brush using model airplane dope, that was before the days of ICs or SMDs. The smallest footprint was a 1/2W resistor or TO5 transistor. Most though have been done with hand drawn art work photographed on litho film and used on boards sprayed with photoresist, and etched in ferric chloride. A number years ago I switched to copper chloride as the etchant, it is slightly slower than ferric chloride but has a number of advantages, not the least of which is it never wears out, hence no disposal problems.

I had heard about using laser printers for the resist pattern but didn't do any thing with it till the #100 issue of MEW came out with a detailed description of the process. It wasn't till a few years later that I got a laser printer and could try it. I had already been using ExpressPCB for other things so it was a logical extension. I have found it much easier and faster than the photoresist method (other than the clay problems), but I'm not sure how you could reliably transfer the pattern on a large board. (The largest I have ever made was 8" x 10" double sided. although I can't see myself ever having to do that again).

Has anyone considered the rapid PCB making services from China. 10 boards for $10 from an Eagle file. May be worth investigating http://www.pcbway.com/

Edited By Brian Oldford on 30/01/2017 22:04:25

Thanks for the lead. Designed a PCB for an 8M2 Picaxe project, sent it off 2 weeks ago and received today first class job and £17.50 delivered for 10.

Sorry for the shaky pic, board size is 55 x 33mm

Peter