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4Sep/10Off

Laser etching

After I built my heated bed controller, it was time to create a PCB for it. Especially, because people had trouble to build the controller.

So the evolution of home-made heated bed controller began:

Warning: long article ahead!

So I began the work. I discovered the program called Fritzing.
Which is an amazing program if you are prototyping.
Is exactly what I needed, so I quickly digitalized my breadboard design:

The program also capable to transform the breadboard design to schematic and pcb. So I thought it is he most simple way to manufacture the board. But turned out the ratsnest is completely unusable and the pcb manipulation is extremely slow:

Fritzing is supporting breadboard, schematic and pcb editing,
and autoupdate each of them, while you are editing one of it.

This feature turned out to be the real dealbreaker, as it messes up the original breadboard design. And also couple of other smaller bugs, like you cant connect multiple wires to a single device, you always need to put a breadboard which ruines the cleaniness, and makes the breadboard view overcomplicated:

So at the end I spent 3 days working on this simple pcb, and finally I decided to redo it in KiCad when the final etched board contained miswirings (because of the constant redrawing):

I would also like to note, the developers were really helpful and responsive,
so I will definietly keep an eye on this project.
It has a real potential, and for breadboard drawings it is already useful, like for article drawings!

Traditional Toner transfer method

I would also like to show you, how I created pcbs in the past.
I used the toner transfer method, which is really popular.
The method itself is really simple.

1. Search a suitable size raw pcb:

2. Cut off the right size from it:

3. Clean it throughfully:

4. Print your pcb design on a "etiquette paper", and using a hot iron, stick the paper to the hot pcb:

5. Put into water, and wait until the paper cames off the pcb:

6. You can help the paper gently. Now it came off:

7. Using the corrector on the above picture correct the pcb, where the melted toner powder is missing:

8. Put the pcb into your favorite etching solvant. Here is my chemie "arzenal":

(dont look at the pcb, it is made using the below detailed laser etching method)

There are mainly two options:
- FeCl water solution (I bought a ready made solution. Its under my hand, you can only see the bottom half of the flacon)
- Hidrochloric acid (HCL) and Hydrogenperoxide (H2O2) solution (10:1)
(more dangerous, because Cl2 gas develops during the etching process)

9. Clean the toner painting off of the pcb using aceton or nail cleaner:

10. Using tin solution, protect the copper from oxidasation:

11. The final board:

As you can see it is ugly and the process is slow and error prone, especially the ironing part.

The more sad part, that it could not fitted on the arduino board;-\

About a millimeter its smaller then it should be.

So I stand back, and thought a bit. I had 4 buyers, who had trouble to assemble the
heated bed controller shield themselve. The above method is simply
too slow. Also I decided to redo the circuit in Kicad, to be able to professionally
get manufactured the boards.

I just met accidentally with a guy who recently bought a laser cutter. And I had the
crazy idea, why not do the pcb using laser cutter after all?

I talked with him, and he agreed, that I can try out his laser cutter, and do several experiments.

Evolving of the laser etching process

I had an idea of covering the pcb with Kapton tape, and burning off the tape using the laser cutter.
Also Chris wanted to use the Kapton for solder mask.

I had really high hopes, when I travelled to another Town to the guy.
For test I used Chris' extruder controller board, because it is complicated enough and use many small traces.

Here is the laser cutter working:

Here is the top and the bottom side of the board done:
top:

bottom:

And also some closup photos, where you can see, that the Kapton itself is burned nicely
away, but the glue, which is under it stayed and gathered all the smoke:

The another closeup:

I etched them. Top:

Bottom:

Two closup pictures to show you the problematic areas:

Trace completely disappeared:

So this experiment was a complete failure. I also tried out Chris' idea, of using the
Kapton tape as solder mask. It is not working either. The burned glue prevent
soldering, if you try to clean it off, you clean also under the remaining Kapton tape too:

Try 2:

Try 3:

I even tried with some resin/flux which helps soldering :

So this idea was not working either.

The final process

We simply painting the boards with regular black paints, and tried out.
Here is a picture during etching (using hydrogenperoxide and hidrochloride acid):

The result was astonishing! Here is after etching (black paints still not removed).
Top:

Bottom:

I cleaned up the board using nail cleaner:
Top:

Bottom:

And tined the board:

The final result is almost perfect. There is only one problem left to be solved. And it is the
offset of the bottom and top layer:

For this I will manufacture a tool, so no offset between the top and bottom layer.
(the raw pcb is not exactly square)

Finally I changed the design to not need that many copper to be etched off.
So here is the final pcb, etched, tinned:

And also working in his all glories:

(Im really sorry for the noisy picture. Had not enough light in the room. And I gave away all my present heated bed controllers (mine included), so I cant update the picture before the end of September)

Finally I think it worth the hassle. Especially for me, as I had very few buyers in the past, so
cant really charge people the cost of manufacturing that few pcbs.

Also for prototyping this method works awesome. Even for this simple circuit I etched 4 different version.

Also a big warning for my buyers:
DON'T disconnect the heated bed shield while the arduino is powered up!
It will kill the output leg of the arduino. I killed already two legs of mine.
Dunno exactly why it happens. (maybe this is the fault of the SSR relay).

Next article will be a little heated bed news. (Im already at version 1.7)

Comments (16) Trackbacks (0)
  1. In the final process, how did you apply the black paint to the copper clad? I am missing something there, but WOW those boards look awesome. Please share more about the final process.

  2. I painted the boards in a factory where they paint electrical motors using spray and compressor.

    I dont know the exact specification, and will not know before 28 of september due the “painting guy” is on vacation.

    I will write it here, once I know myself too.

    If you read on the net, others suggest simple black paint spray. We tried some more, but this one worked the best.

    Sorry, I cant answer currently your question.

    Best regards,
    Laszlo

  3. So did you laser etch the black paint?

  4. I ended up not understanding. Did you paint the board with black paint and later used the laser on it?

    What did laser for the paint? did it removed/burned the paint?

    So the acid aren’t able to remove the paint from the board?

    How did you do the holes for vias?

    What minimal size for tracks can you get? 0.25mm? 0.1mm?

    Thanks for sharing!! Good work!!

  5. nophead:
    1. paint black the both side of the raw pcb. (I think we left for a day to drying)
    2. Burn the black paint with a laser cutter, where you want to etch away the copper. It is almost completely disappear, if not, while you etching with a sponge, you clean the smut/soot/grime.
    You can see, how nice it burned away on the “chemie arzenal” picture. The board is after the laser cutter and just before of etching.
    3. etch the board

  6. casainho:
    > I ended up not understanding. Did you paint the board with black
    > paint and later used the laser on it?

    > What did laser for the paint? did it removed/burned the paint?

    Look at my answer to nophead.

    > So the acid aren’t able to remove the paint from the board?

    No, this dried black paint withstand both H2O2+HCl solution, both FeCl solution. Also it has a thickness. So even if you manage to clean something off with a sponge, there is still paint protecting the copper.

    But it is easy to clean off with a “nail remover”. The nail remover what Im using you can see at the point 9. I believe pure acetone would work equally nice.

    > How did you do the holes for vias?

    After I etched the board, I drilled it with a 1mm drill bit. Where vias is supposed to be, I used leg of resistors. Basically I used up the legs of the parts what the circuit requires. Only the big green connectors needed an 1.5mm drill bit.

    In future I plan to do it in a CNC machine (and later in my reprap machine), and drill the holes with 0.8mm. Also I have seen a “vias tool”, where you apply the via, just like a rivet. By hand. Dunno where I have seen on mouser or on farnell.

    > What minimal size for tracks can you get? 0.25mm? 0.1mm?
    Sorry I can not really answer this question, because dunno why I was only able to draw one width of traces in Kicad. Looks like the kicad, what Im using contains this bug, because I have not really seen anybody else having this problem. This is the Kicad coming with ubuntu 10.04 i think. (2010-04-19 BZR23xx)
    The ubuntu has this package: bzr2407~karmic-1

    But if you look at the “top” and “bottom” text, it is really thin.

    I think, it is limited by the resolution of the laser cutter.

    Maybe I will do some of the Chris’ controller board, just I cant do it any more experiences before 28 of September.

  7. Many thanks for your info. Another question, your laser is of 40W? how much did it cost?

    As for rivets, you can buy on Ebay relative cheap bits of 0.6mm and use this 0.4mm copper rivets: http://www.megauk.com/through_hole_rivets.php

  8. casainho: The laser is a 40W CO2 laser, yes.
    It costs about 1400-1500 EUR and has a 200×300mm working area.

    However it uses the exact same belts as rapman machine, and the carriage is looks very similar to Mendel, the only difference, that it is made of aluminium. (ie. it uses the same 624 bearings).

    If this machine was mine, I would definietly change the electronics inside it, because it comes with some chinese CAD program, which is hardware keyed, and buggy as hell.
    Only the “brain” board should be changed, and discover how is it wired to the laser regulator board. (I think through a pwm output). Other then that it has two stepper output, and 2 endswitch input. Seems pretty simple to me.

  9. Hello,
    really nice post and good progress.

    I really like the idea of lasering a completely painted board.
    As I do my own boards too, with toner transfer, I am really curios about your tin solution. Would you mind explaining what it is and how it is applied?

  10. DarkerMark: At point 10, you can see the photo of the chemical tinner.
    I simply put the etched pcb into this solution for 10-20minutes until the copper becomes silver colored. I refill the tinner into its original flacon. As you tin more and more board, it becomes slower and slower, but I dont mind.

    The product is TN160, and produced here by Wolf Inc. Here is the product homepage:
    http://www.wolf.hu/gb/index.php?id=tn150

  11. You can laser engrave again to make a “silk screen” mask. This allows you to put text and symbols on it for guiding people through the assembly process.
    That’s what I did here:
    http://picasaweb.google.com/erikdebruijn1/RepRapDev#5402063834069457554

  12. Erik: Im not sure, how well I can solder the burned paintings.
    (Ie. I need to paint one more time the etched, tinned pcb, this time for the texts.)

    I will definietly try it out, since, I can put a protective paintings on it. Would be awesome to produce black colored pcb. It’s stylish after all…;-)

    Nice idea!

  13. Laser etched black paint is a great idea.
    Another blogger built a low power laser etcher 1-5 watts I think. It would probably have the power to get through the paint, he cut a hole in a jewel case.
    This could be an easy mod for a reprap.

  14. … for perfect aligning the two sides you should drill 4 symetrical holes in the edges and the same holes in the bed, so you can turn the PCB without misaligning …

    Viktor

  15. VDX: I only thought about two horizontal holes at the middle line of the pcb.
    But yes, Im on the problem already;-)

  16. Hello :-)

    Did you made more PCBs with this method? what is the smaller pitch you did? 0.5mm??

    Did you try to make the holes using the laser? or simple cut the PCb with the laser after being etched, in parts without cooper?

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