OHT or press n peel blue??

Frequently asked question on the subject of designing, creating, producing printed boards, veroboards or perfboads and on point-to-point construction techniques.
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chicago_mike
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Post by chicago_mike »

So as you may know, Im trying to get a process down for etching and what not. I am close and was just filling in some gaps here and there.

For toner transfer..err...transfering the toner to the pcb... I have now used uv but 2 uv boards came out poo and will wash the resist off.

Now for the question..can OHT sheets be iron'd on to a pcb, just like photobasic gloss or press n peel :?: Should I expect to lose the transfer on the pht sheet and possible not be able to reprint on that side?
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rackham
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Post by rackham »

If you mean the clear acetate sheets that are designed for overhead projectors, then yes, they work well (for me). If the iron is too hot then you can smear the toner though.

I prefer it to photo paper because you don't get the white residue that you have to scrape off and you don't need to soak the board.

I've not tried PNP blue but I'd imagine that's probably the best solution, given that it's actually designed for the job!

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Post by chicago_mike »

coolness. I'll have to try this method then. ty, :)
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Post by decora »

sorry for being off topic but what about silkscreen? i was at a printing shop today buying supplies and saw some sample pcb screens. too many people in the shop so i didn't bother to ask. will investigate further on my next visit.

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Post by rackham »

decora wrote:sorry for being off topic but what about silkscreen? i was at a printing shop today buying supplies and saw some sample pcb screens. too many people in the shop so i didn't bother to ask. will investigate further on my next visit.
Better again (in my experience), particularly if you're doing a number of identical boards.

Less convenient for one-offs because you have to piss about with photo-emulsion etc

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Post by roseblood11 »

Thin and gloosy sheets of paper from a catalogue work best for me.

I use this one:
http://www.reichelt.de/?;ACTION=72;LA=0 ... 79c6f2bda8

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Post by chicago_mike »

So far the UV method I am doing is working out the best. SUPER clean traces. NO smearing what so ever. I got too much smearing with any other method.
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Post by madbean »

I've recently switched to photo paper (Staples) from PnP Blue. I get much better and more consistent results with the photo stuff. It's impossible to smudge or over heat. Only downside is it takes longer to get the board ready to etch. On the upside, I almost never have to dress it up with sharpie.

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Post by rocklander »

madbean wrote:I've recently switched to photo paper (Staples) from PnP Blue. I get much better and more consistent results with the photo stuff. It's impossible to smudge or over heat. Only downside is it takes longer to get the board ready to etch. On the upside, I almost never have to dress it up with sharpie.
do you just peel it back the same way one does with PNP, or do you need to disintegrate the paper type thing?
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Post by madbean »

I iron to the point where I can start to see the traces just barely through the paper. Then I put it in the freezer for about ten minutes. When you heat the copper, it expands a little, and freezing it down quickly helps harden the transfer, I found. Then I soak it in cold water with a little bit of dish soap. After 15-20 minutes I peel back the top layer of paper. At that point there will still be some paper sludge covering the traces, but you'll see them fairly well. I let it soak for maybe ten minutes to loosen up that layer. After that, I generally peel a little more or rub the paper with my finger to get more off. Then I use a scrub brush to remove the remaining paper. If you do this right, you will not rub the traces out at all. They only rub off if your transfer was bad. You can use the scrubber to remove everything you don't want. No need to use a toothpick or knife. One important thing: keep the paper immersed in water when you are scrubbing. It dries really fast, and only comes off when it is wet.

The traces will usually come out near perfect. Sometimes there is a little touch up needed, but not nearly as much with a rough PnP transfer.

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Post by Jarno »

I use Epson photopaper for inkjet in my laserprinter, and that works fine as well, resolution will always be lower than "proper" UV transfer, but good enough for analog stuff. I do get white stuff in between the toner that I have to clean away with a toothpick. A bit of a pain, but I don't dare to be too agressive with a brush (even though the toner layer is pretty thick and sticks to the board like a champ).
Works for me, but ironing is a bit fiddly initially. If you have one or two corners sticking to the board it almost never shifts. Small boards are somewhat harder because you need to hold down the paper on the board AND make sure you don't iron your fingers :)
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Post by rocklander »

madbean wrote:I iron to the point where I can start to see the traces just barely through the paper. Then I put it in the freezer for about ten minutes. When you heat the copper, it expands a little, and freezing it down quickly helps harden the transfer, I found. Then I soak it in cold water with a little bit of dish soap. After 15-20 minutes I peel back the top layer of paper. At that point there will still be some paper sludge covering the traces, but you'll see them fairly well. I let it soak for maybe ten minutes to loosen up that layer. After that, I generally peel a little more or rub the paper with my finger to get more off. Then I use a scrub brush to remove the remaining paper. If you do this right, you will not rub the traces out at all. They only rub off if your transfer was bad. You can use the scrubber to remove everything you don't want. No need to use a toothpick or knife. One important thing: keep the paper immersed in water when you are scrubbing. It dries really fast, and only comes off when it is wet.

The traces will usually come out near perfect. Sometimes there is a little touch up needed, but not nearly as much with a rough PnP transfer.
thanks for that clear, concise explanation.
will try this method for sure some time.. I still have PNP so will likely finish that off too, but I'll experiment with a bit of this.. I'm intrigued :hmmm:
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