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ArcticMyst Security by Avery

Best way to burn off paint?

NsN

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Feb 4, 2011
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Hi,
i'm finally getting ready to try my first laser builts. I have two different lasers, a blue 405 nm one and a red 650nm one from an old DVD burner.
I drive the blue one at ~80 mA and the red one at ~170mA.
So far i am able to cut various papers, (even white ones) and mark wood and other things. Judging by cutting power, it seems to me that the red one is stronger than the blue one.

However what i'm really interested in, is removing paint from a copper clad board. It is only thin layer of copper 35um (typical homemade circuit board) but the heattransfer might be a problem. I don't really care about the color, but i suppose black would be easiest.

So far i have tried various flat black paints from our local hobby store, as well as a couple of black permanent markers. I manage to mark the paint, but it only burns the very top layer, normally i can rub the mark of with my finger.

Do you have any suggestions for a good paint to try? I'm guessing that the hobby store paint is to thick, while the permanent markers are to shiny.
Or do you think getting a 500mW 405nm diode would be enough to remove the paint?

Bye,
NsN
 





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Have you tryed copy toner it could be applied by dusting the board with it then use
your laser to melt it to the surface where you want a trace or a pad to be and
then blow away the unmelted toner then you can etch the board.

Did I just come up with a new way to make ckt brd's ? or is this being done :thinking:
 

NsN

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That sounds interesting, i'll have to try that.
I'm a bit weary of the toner, because in my experience so far it's a bit nasty, very fine and ver dirty. But i like the idea of heating the toner to stick it, instead of removing it.

There are a couple of variants of the toner transfer method, one involves direct printing on the copper with a laser printer, so it's not a completly new idea, but i don't think it has been done with a cnc laser.

One advantage of removing the paint, rather than curing it, would be that i can prepare boards and don't have to deal with any messy colors, when i want to produce them.

I envision something like this:
- Have large amounts of copper clad board pre painted in black
- When i need a board, i remove the paint where i want to etch
- etching the board
- drilling
- done

It would remove the step of transfering the layout from the paper to the board either via toner transfer or photo exposure.
I have seen some who selectively expose the board using a laser and photo positive boards, but that still requires the development of the board. I want to slim this down as much as possible

I can also see a further more elaborate process:
- Have pre-painted base board
- Cut to size in CNC using milling head
- Burn of paint using laser head
- etch
- Burn of remaining paint
- Coat in black paint again
- Remove paint from pads and vias with laser
- paint in red / blue paint, depending on laser type
- remove paint from pads and vias, and everywhere where you want a silk screen
- drill holes using CNC drill head

Of course this would require quite a lot more than the usual for home etching PCBs, but most of it is just applying a coat of paint to the board. And the various layers should fit very acurate over each other and way more precise than i can do at the moment.

In a german forum somebody posted some results exposing a photo positive board using a laser and he got very accurate results down to 1-2 mil (of course whether you can reliably etch this at home is a different question)
 
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It's a neat idea, but cutting-lasers are not very useful for mask creation. Even if your laser is good enough to burn paint, you're able to control the laser precisely enough, and the copper doesn't transfer heat away too quickly, how are you going to burn away regions of paint using the fine point of a laser? Even isolating traces with a half mm of gap will be a pain. It's like doing shading with a fine-point pen. I'd stick with the iron-on toner method or just send your masks to a PCB shop to have it done professionally.
 




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