Spray on Photoresist- How Successful is it. - diyAudio
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Old 22nd May 2008, 12:41 PM   #1
Mooly is offline Mooly  United Kingdom
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Default Spray on Photoresist- How Successful is it.

Wondered if anyone has ever used the spray on Photo-Resist coating for PCB's and had good consistent results with it. I've never tried it but keep wondering.
Thanks Karl
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Old 22nd May 2008, 01:06 PM   #2
Nordic is offline Nordic  South Africa
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Yep it works fine, but sure you will have a few mishaps the first couple of tries...

Avoid the Cramolin brand, Positiv20 works quite well.

You need to cover the board in as thin a coat as you can consistantly apply without any uncovered pinpricks left...

I prefer spraying mine at night, in sunlight it always looks like I applied less than I did, it is painfull dealing with too thick a coat during the development stage...

I use outdoors UV exposure, I would say about 5 minutes would be right for the UK, 4:30 for bright sunny days.
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Old 22nd May 2008, 05:58 PM   #3
Mooly is offline Mooly  United Kingdom
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Hi Nordic,
Good to know it works O.K. I was worried about not getting it "thin and even". The one I have in mind is by Electrolube, which is about 11 GBP here. So it could work out cheaper as well.
One thing I have only just thought of, once sprayed you'll have to use it straight away so it does not get contaminated or "exposed". Worth a try I think Thanks for that,
Regards Karl
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Old 22nd May 2008, 07:10 PM   #4
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I dry mine overnight in a light tight biscuit tin.

It works OK, but not perfectly. For all the effort involved, I prefer to laser onto glossy paper & iron that onto the copper. WAY cheaper, and much less work.
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Old 22nd May 2008, 07:14 PM   #5
Mooly is offline Mooly  United Kingdom
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When you say "not perfectly" what problems have you ?
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Old 22nd May 2008, 08:01 PM   #6
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Getting CONSISTENT results is hard. Some work well, some not. I think it is very dependeant on the spay uniformity, and the quality of the artwork.
Generally the uniformity of the resist varies over a board, unless its a very small board. Some areas over expose, other dont.

Maybe true photographic artwork would help, but it costs too much for once offs.
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Old 22nd May 2008, 08:56 PM   #7
Nordic is offline Nordic  South Africa
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Once sprayed and dried it just needs to be kept out of light, I just turn mine over and put it face down in a drawer on some cloth to avoid scratching.
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Old 23rd May 2008, 07:48 AM   #8
Mooly is offline Mooly  United Kingdom
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You've convinced me, will stick one on the next order.
And what happened to Twiki
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Old 23rd May 2008, 08:01 AM   #9
Nordic is offline Nordic  South Africa
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Twikki sad, Twikki leaves....If I could have anything I chose as a child, It would have been Twikki...
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Old 23rd May 2008, 08:07 AM   #10
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With some pointers from Nordic I've done quite a few boards, including some double sided boards down to 12mil resolution without breaking a sweat. Works fine everytime, although it took some practice in the beginning to get the process right. I must admit that I'm using the missus' imagesetter at work to do the artwork, so that helps.
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