HerbertMunch

Also, on the dipping front, I bet the liquid stuff wouldn’t reek as badly as the spray, or at least it wouldn’t be airborne.

The problem with the spray is that you need to do it under tungsten lighting, with the door shut to stop the daylight.

I really need to get a respirator, or maybe take up late night spraying

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Chris

3v0

You can eliminate the bad cm by giving the liquid some place to go. Tape/glue/connect/butt a bit of scrap PCB to the bottom of the board you are spraying and the excess should run down onto it. Providing the joint between the boards is not too loose.

Interest in photo resist has been reduced by the use of toner transfer.

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HerbertMunch

But wouldnt taping something to the board not produce similar undesirable effects or at least end up with part of the board not being covered?

Also,
Something that really sets the commercial stuff apart from the diy, the black film that they stick to the sprayed boards, to prevent unwanted exposure.
It allows you to work with the board before you expose it. i.e cutting etc, thus making it possible to mass produce diy-ed boards and store them for later use.

I was thinking maybe experimenting with different black plastics (i.e. bin bags, etc) and possibly sticking it to the dried diy boards with spray mount adhesive. I.e. sprayed to the plastic and then sticking the plastic to the board.

I’m going to cut out some small pieces of board and coat them, and then see what it takes to expose them through different black materials. Also do a few control tests with boards exposed through a mask by tungsten, fluorescent and daylight.

I cant really do a tutorial justice until i have a camera ( and another can of resist).
Interest in photo resist has probably gone down hill, due to the expense of the pre-coated boards, and the difficulties associated with spraying your own.

No matter how well toner transfer can work out, it will never be able to recreate the same level of detail and repeatability that the resist can. I just couldnt see an institute such as a university ironing on bits of magazine paper!

Its off putting, having no information to work with. But i suppose once ive finished my experiments, i will be able to publish the findings for others here at the forums, and hopefully convert a few of you from the dark side

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Chris

pitronix

I just tried to help. I found it easy to do. On the other hand I do have a lot of experience in silk screening as well as other printing techniques since I worked in that field for a couple years. And it is worth learning in any case since you can do so much more things. But I agree that it could be hard to start.

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jpanhalt

If the commercial boards you get come with a plastic protective coating, there is a chance they are made by laminating the photoresist, not spraying it. See:

http://www.megauk.com/datasheets/518..._Laminate).pdf

Here are some additional links to laminated photoresists. Note the low temperatures used. Once laminated, processing with the positive-resist version is identical. These links also include some good technical information on making developing solutions, etc. Laminating the resist avoids all odor and most of the chemical risks.

I have put an asterisk on the two links I found best. John

http://www2.dupont.com/Imaging_Mater..._US/index.html
** http://www2.dupont.com/Imaging_Mater...eets/GM100.pdf
** http://www2.dupont.com/Imaging_Mater...ins/index.html
http://www2.dupont.com/Imaging_Mater...ech_forPCB.pdf

HerbertMunch

ok thanks.

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Chris

HerbertMunch

I bought some of the spray that this webpage didnt recommend (PRP green spray) just to see why he didnt recommend it.

excuse my french but its absolutely shit. Its has the consistancy of water, and it pisses out all over the place when you use it.
The positive 20 spray(purple) is thick and syrupy, and when you spray it vertically it will leave a nice coating. This PRP crap just runs right off onto the box below, leaving a rubbish coating.

I CANNOT STRESS THIS ENOUGH, STAY AWAY FROM PRP!

I bet this stuff is responsible for quite a few people being scared away from spraying their own.

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Sputnik

Sorry to dig up a seemingly dead thread but does anybody know where to get spray resist in the US?

Or perhaps small quantities of resist film?

Think and Tinker sells film but its expensive, $85 for 12inx50ft roll. I guess thats not that expensive for what it is, but an $85 whack in the wallet is crude. Oh, and its negative acting. Which would be fine I guess.


For all of you wondering about the Photographic method using pre-coated boards, THERE IS NO OTHER WAY TO GO. I have gotten 100% sucess using this method.

And guess what, despite all of the info saying it isnt possible I do it all with an inkjet printer, always have and never had a bad board due to the transparency.

If ive had a bad board it wasnt due to the methodology, just me not paying attention to the clock, or forgetting the board was in the developer.

Here is a small board I just made using this method. I have made even smaller boards with tiny QFN package ICs etc. with even better results.

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	FILE0009.JPG (115.8 KB, 13 views)

3v0

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jpanhalt

My impression is that inkjet was the preferred method, particularly in the early days when lasers were 300 dpi. It is not so much the opacity of the ink, but the lack of defects that benefits inkjet method. The ink flows just a little to fill defects. With laser, that does not happen.

People are using newer laser printers the photo-resist methods and report good results. A few are adding the green toner transfer from Pulsar or the equivalent to the laser transparency to correct the defect problem. I plan to try that in a few days.

As for obtaining the laminate film is smaller amounts, I agree. I think it would be fantastic if one could get just a foot or two to experiment with.

John

Sputnik

Mega in the UK sells a kit that contains 5 8.5x11 sheets of resist film, however I cannot find these sheets on their site, just the rolls.