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Old Nov 07, 2012, 02:29 PM
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Letchworth, Great Britain (UK)
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Question
Best etch-resist pen for PCB?

I bought a starter kit for making my own PCBs a while back, and over the past couple of days I've eventually got around to making a couple. I've been hand-drawing the tracks on the copper with the supplied pen -- a Staedtler permanent Lumocolor -- and have had good results (within the limits of my drawing capability) apart from one thing:

Each time my etch has taken about 20 minutes, using sodium persulphate solution. But each time I've had to twice remove the board from the solution, wash it, dry it, and then re-apply the pen because the ink has been eroded by the etch solution in places, and copper is showing through.

So, any advice please on what is the best pen to use? Do you normally have to touch-up your tracks during an etch?
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Old Nov 07, 2012, 03:42 PM
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Borrow the ladies red nail varnish.
Or being tight I hate to say it but this one stands up to ferric chloride extremely well.

Did you scouer the board before using the supplied pen?

Dave

http://www.megauk.com/artwork_aids.php

100-031 RA615 Artwork ultra fine touch up pen 0.5mm 12.00
.
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Last edited by orraman; Nov 07, 2012 at 03:47 PM. Reason: dd
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Old Nov 07, 2012, 04:04 PM
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abenn,

The Dalo pen is the only one I've found that doesn't come off in the etchant...

http://www.maplin.co.uk/dalo-etch-re...arker-pen-2105

I'm currently trying one of these though to see how it stands up...

http://www.tigerpens.co.uk/acatalog/...FePHtAodSSAA3A

Don't get one of the metallic ones because the metal particles dissolve in the etchant.

A.
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Old Nov 07, 2012, 06:32 PM
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Just tried a test piece using the Edding 780 extra fine pen, seems to work OK for making fine tracks.

A.
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Old Nov 08, 2012, 03:12 AM
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Thanks for the suggestions. I didn't scour the board first, so maybe that's part of the problem. So I'll do that with my next etch, and see if it helps.

Maplin is handy for me, so I'll get one of their Dalo pens next time I'm round there. In fact, it's their starter kit I'm using -- surprising it has a different pen from the one they sell separately.
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Old Nov 08, 2012, 04:51 AM
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I've never had much luck with any of the standard type felt tip pens, the ink isn't thick enough. The Dalo pen is OK but the tip frays after a bit of use and fine tracks are no longer possible although the paint pens are looking good for fine touch-up on the toner transfer system I use.

A.
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Old Nov 08, 2012, 06:29 AM
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No doubt I'll move on from hand-drawn before long. Toner transfer looks good, but I don't have a laser printer; photo-resist is looking good, provided I can make myself a cheap light box.

Just looking at some web sites now, it might be cheaper to simply buy a basic laser printer -- is any manufacturer's toner better than others for toner transfer?
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Old Nov 08, 2012, 06:52 AM
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Abenn,

I use a second-hand HP 6L on probably it's original cartridge, although the toner isn't particularly thick, one thing I discovered is that if I scour the copper before ironing on the TT material it makes the etchant seep underneath the toner and leads to all sorts of breaks in the tracks. It seems much better to polish the copper Brasso then wash it before applying the transfer. Temperature and pressure are important also with this method. I use a filming iron set to about 150C.

A.
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Old Nov 08, 2012, 07:26 AM
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I bought a Samsung its was on special but appears not that special still same price last year

It's pretty good but toner not the best but works. So some toners are great but your looking at dropping a lot of money for printer and cartridge's cost the earth. before i bought printer i used to get prints done at local shop and there printer was perfect, once they let me tweak setup . Still total pain when you want minor changes.
The Samsung i got now take a while to find my best setup but i got lucky with some high gloss paper btw High Gloss Photo paper will not work with laser printer, just make a mess. It appears the paper is made up from layers of plastic+paper and the back of sheet is matt plastic! Toner just grabs enough and can still handle it. This is the good bit when I've ironed it on i found i can carefully pull it off with out water and I have 100% of toner on pcb. When i used normal paper i always get paper/toner fluff. Bad new is some one gave me paper with no label so don't now brand or where to buy more
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Old Nov 08, 2012, 08:43 AM
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The Seno rub down transfers in the Mega link above are also available from rapidonline and do produce neat workman like boards but do require finer cleaning of the board.
For more than one copy of a board the transfers can be used on transparent plastic for use with UV and photoboard.

A visual light-box and strong magnification is good for checking transparencies for pinholes. Nothing special needed, a low wattage, long life (fluorescent) lamp under glass. Touch up as best you can then tidy up scraping with a scalpel.

After that all you need is software and Laserstar sheets from Rapid or Mega which can be used in a laser photocopier.

As order code HX02C Maplin sell the Lumocolor 318 F for 3.99. Or from Mega for 1.89.

I got mine for 1.90 ordered in for me at the local stationers.

Dave
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Old Nov 08, 2012, 02:34 PM
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Just thinking aloud here ... I know that "proper" light boxes use UV light to expose the photo-resist, but is it possible that I could get a result using my scanner? I could have it do several high-quality (i.e. slow) passes to expose the photo-resist. The advantage of the photo method, for me, is that I can presumably print my masks with my HP inkjet onto projector film.
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Old Nov 08, 2012, 03:44 PM
kad
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Quote:
Originally Posted by abenn View Post
No doubt I'll move on from hand-drawn before long. Toner transfer looks good, but I don't have a laser printer; photo-resist is looking good, provided I can make myself a cheap light box.

Just looking at some web sites now, it might be cheaper to simply buy a basic laser printer -- is any manufacturer's toner better than others for toner transfer?
Avoid Brother, their toner is a higher melting point than others. I use a cheap ($99 x-mas sale) HP unit and cheap, non-waterproof (important!) inkjet photo paper.

-K
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Last edited by kad; Nov 08, 2012 at 03:44 PM. Reason: typo
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Old Nov 08, 2012, 05:18 PM
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Given enough exposure your scanner might work but?

There are specific wavelengths of UV for PCBs but you could search for the many different DIY systems have been used successfully, from fish tank tubes to insect zappers to UV LEDs placed in scanners and down to standard fluorescent tubes and sunshine.

Interesting info and the truth about Typesetters if you can find one now.
http://www.electricstuff.co.uk/pcbs.html

Dave
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Old Nov 09, 2012, 06:53 AM
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Yes, there seem to be cheap HP lasers at around 50 here -- but the cartridges cost the same again!!

I'm going to try a test strip of photo-sensitised PCB (from the starter kit I mentioned earlier) on my scanner, and see if it'll work. I'll report back.
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Old Nov 11, 2012, 05:58 AM
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Needless to say, the scanner is not practical. I divided my strip into eight, and did 5 scans for each exposure (i.e. 40 scans for the longest portion), but all the photo resist immediately dissolved off when I dipped it into developer.

So, I've ordered a bunch of cheap UV LEDs from eBay for my next test ...
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