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Author Topic: Ink for silk screen pcb printing  (Read 2463 times)
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Orlando, FL
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I hope this one is right category for my question.

I recently bought a silk screen kit and trying to print a pcb board design. I successfully created a pattern on the silk (silk number is 120) and I'm ready to print but I could not find an ink for the job. I used the fabric paint comes with the kit and an acrylic paint but they didnt work. the ink spreads all over the copper board and lines touch each other.

Can someone recommend me an ink for the task?

Thanks,
Tuncay
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Pottstown, PA
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As a screenprinter and Arduino/electronics hobbiest, I am interested in this topic also. I don't think you will get any decent resolution using a mesh count of 120 and way too much ink will pass through with those large screen openings. Resolution and control of ink flow will be much more likely attainable with a greater mesh count especially since the ink used for pc boards will likely be much thinner than textile inks. I have 230 screens and would try that if I were to attempt to print pc board masks but my gut feeling is that an even higher mesh count will be needed. You may also need a different emulsion or capillary film that will hold up to the ink used for pc board masks. - Scotty
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Orlando, FL
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I found an academic article and that one was saying #120 is good for pcb boards, but looks like I bought wrong fabric.

I will make a research for emulsion when i learned the ink type. Thanks.
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Hey there, I use 120 mesh count, and for the ink I use Plastisol or PVC ink, is very thick, for the components mask I use some kind of thinner, something called isophorone to make a very thin layer.

I'm having a little trouble when printing SMD pads and traces, I'm thinking of buying a 300 mesh to see what happens...

hope this helps

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Any news?
I'm interested in this too, and would like to know if anyone is finally arrived to any good solution.

mtD, could you please post the link of the academic article you found about this?
Any other link with details on the process would be appreciated.

Many thanks
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Orlando, FL
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Nope, I could not found a paint for silk screening. I gave up on silk screening for now..
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Pottstown, PA
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Had some success with screen printing on copper clad board. The widely used ink for screen printing on textiles is plastisol. In my search for an effective method for DIY printed circuit boards I became aware that a common method is to use a transfer method involving a laser printer. The objective there is to transfer the toner(which has a plastic component) to a piece of copper clad board. The toner resists the etchant. Being a screen printer, I happen to have a screen available and some plastisol (which has a plastic component) so decided to try it. It worked. Below is an image printed using regular plastisol ink through a 230 mesh screen. The actual size of the graphic is 2" across. The ink was cured to 320 degrees. The ink held up very well under the etchant with no signs of breaking down, pitting, undercutting. etc. I wouldn't try this method with a low count mesh such as 120 TPI.

With all that said, I will be using this method: http://arduino.cc/forum/index.php/topic,142714.msg1071644.html#msg1071644
It works very well without sacrificing a screen on what may be an unproven design.- Scotty

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I'm a bit confused..
Scotty, you are in fact using toner transfer method for creating pcb etching copper, isn't it?
I mean, is that on your photo copper?
Because what I'd like to do is screen print over the solder mask on the pcb, to reference components with labels, with (usually) white ink.
Here is an example:
http://www.pcbfabrication.com/PCB-fabrication/PCB-fabrication-Images/PCB_silkscreen.jpg


So, my steps would be:
-etch the copper board with UV and transparencies masks, etching the photoresist and then the copper with ferric chloride
-apply a layer of solder resist mask (UV curable solder resist mask for pcb repairing, http://dangerousprototypes.com/forum/viewtopic.php?t=2383 )
-finally, and that's what I'm searching for, apply the silkscreen layer, the labels for the components on the board, as the image in the link above.

I think that there exists some kind of ink which is UV curable, ie after have the ink applied on the board let it expose under UV light with a mask printed
on a transparency and then wash out the exceeding ink..
the same procedure of UV solder mask, but I can't find that ink!


If I misunderstood what we were talking about, my apologies!
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Pottstown, PA
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I do use the toner transfer method using vinyl instead of paper for the transfer. The photo in my previous post was done via screen printing plastisol onto a copper clad board. It was posted in answer to a member's quest for an ink or paint that could be screen printed and would resist etchant.

I do have a quart of UV cured ink although I cannot remember what I bought it for. Anyway, I understand that it can only be cured using a high intensity UV light source. I tried the sun; that didn't work. The fumes are nasty.

It's entirely possible that you could screen print right onto the PCB at any stage. Not sure but I think plastisol work work. The key would be to use an appropriate mesh.

If you don't mind black printing too much, there is another method. It also involves a laser printer, using the heat transfer method. Print the Label layer onto whatever transfer media you select, but print it as a mirror image. Then heat transfer it to the top side of your board.

- Scotty
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I used the laser toner transfer method for pcb manufacture it was ok but what i also tried at the time was ironing the component image layer on the other side. I did it in exactly the same way, a very light run with pcb abrasive bloc, a clean with acetone and then ironed the printed magazine onto the non copper side (lined up first). It worked well enough, maybe not as strong as the real thing but it didn't come of. Of course the image was black so quite as easy to see but better than nothing.
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OK,
thanks for the hints and sorry for off-topic.

I think I'll go with "toner transfer screen printing" with black toner, but I'll give a try to yellow printed transparency too.
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