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I used a DIY kit and made a PCB milling machine. So far I am happy with it but it is slow and the minimum thickness of the lines is depends on the tip's size.

I want to replace the cutting bit with laser diode to ablate copper layer directly to ablate acid resistant paint so I would overcome the issues I mentioned.

EDIT: As Spehro Pefhany explained removing copper layer with laser requires much powerful laser than a simple laser diode. At this point using a laser diode to ablate paint would be a better way to do this.

Here are my questions:

  • What type of laser diode I need to use to remove ~1 mm thick paint layer?
  • How can I calculate the minimum power I need to ablate the paint layer?

I read about laser diodes, driver circuits, protections (diode itself and human body) but I could not find a decent source about my questions.

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  • \$\begingroup\$ I'm not sure how to calculate the amount of power you'll need but it'll be well over the limit of laser diodes. Even wood engraving machines use gas pumped lasers. Also consider what it will do to the substrate. \$\endgroup\$
    – PeterJ
    Feb 25, 2014 at 2:34
  • \$\begingroup\$ It also likely won't be appreciably faster. \$\endgroup\$
    – Ignacio Vazquez-Abrams
    Feb 25, 2014 at 2:42
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    \$\begingroup\$ I have heard of people using a UV laser to expose a photoresist pcb and etching as normal. However it is much easier just printing a design on to a transparency, like you do using the normal photoresist method. It is also easier to align a double sided pcb that way. Ablating paint or using the photo resist method you still have to deal with chemicals. Which is messy and moderately time consuming. So I suspect you wont save much time, unless you are trying to produce a larger volume. But if you are making more than 5 you may as well get them made by one of the various online outfits. \$\endgroup\$
    – DarcyThomas
    Feb 25, 2014 at 8:48
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    \$\begingroup\$ Changing your question after you got an answer means that Spero's answer no longer makes any sense. Future readers won't understand what he's on about, and voters will downvote him for not answering the right question. If you want to change your question that much, it's better to start a whole new question. \$\endgroup\$
    – The Photon
    Feb 25, 2014 at 15:43
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    \$\begingroup\$ This question appears to be off-topic because it is not about electronic design. \$\endgroup\$
    – Dave Tweed
    Feb 26, 2014 at 16:47

5 Answers 5

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I used a 808nm 0.5W laser diode and it can remove paint from over the copper layer.

I have explained it in the posts of my blog, from buying to the current results. The URL is:

http://gabuleu.blogspot.fr

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    \$\begingroup\$ (1) While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference. Link-only answers can become invalid if the linked page changes. (2) Self-promoting your blog is not a good practice on EE.SE . \$\endgroup\$
    – Nick Alexeev
    Jun 12, 2015 at 0:28
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    \$\begingroup\$ Confirming @NickAlexeev point, the link now states "Sorry, the blog at gabuleu.blogspot.com has been removed. This address is not available for new blogs." \$\endgroup\$
    – Ben Crowhurst
    Apr 15, 2021 at 21:34
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An ordinary laser diode won't cut it (literally). You need something like a Q-switched laser, pulsed at 10's of kHz. The peak power has to be extremely high to ablate copper (>2500°C), and some nasty fumes come off the epoxy substrate, which have to be exhausted.

Even a 40W \$CO_2\$ CW laser won't cut thin metal foil- it just bounces off.

Here's a commercial unit (costs as much as a really nice automobile).

enter image description here

If you really want to fool around with this sort of thing, you can find suitable lasers on the surplus market, but it's not going to be a matter of attaching a little diode to an engraver head.

Class 4 lasers are not toys!

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    \$\begingroup\$ I saw this product and liked it so much but it's price tag (~$175k) is far beyond hobbyist level. \$\endgroup\$
    – dvdmn
    Feb 25, 2014 at 4:27
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    \$\begingroup\$ Watch the video youtube.com/watch?v=PhH05jNyjCk&list=PL2C566A88EF45284C of that beast in operation. It truly is (electronic) engineering porn. \$\endgroup\$
    – markt
    Feb 25, 2014 at 8:37
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    \$\begingroup\$ @markt let's get a NSFWallet tag on that one \$\endgroup\$
    – scld
    Feb 25, 2014 at 20:13
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    \$\begingroup\$ What about this machine?, lpkf.es/productos/creacion-rapida-prototipos-pcb/… Its specs says that it is using 100mW and 355nm, but i am not sure if it is using Q-switching with high peak power, because of its size and power supply specs I am confused. \$\endgroup\$
    – Jairo Andres Velasco Romero
    Apr 20, 2016 at 23:51
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Others are ahead of you on this project: http://www.diyouware.com/

DiyouPCB is a PCB printer which uses a Blu-Ray™ pickup

They are getting some very good results, notably they are still using a photo-resist process and not etching the copper off directly with the laser.

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To answer the original question: it looks like it might be possible to do with a 20 W fibre laser (1064 nm) as documented here: https://www.kurokesu.com/main/2021/01/07/making-fine-pitch-pcb-prototypes-with-fiber-laser/

According to the article, it took about 20 cycles to cut through 0.035mm copper foil with some passes using up to 90% power.

The format of the laser used is a Dual-Mirror Galvonometer (galvo) laser.

enter image description here

enter image description here

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What about this prototype ?

https://www.youtube.com/watch?v=4SNkzoOvoD8 (1st version)

https://www.youtube.com/watch?v=uIIwU29H3E8 (2d version)

It answers exactly to the original question and is home made with some recovery equipment and it seems that it removes copper perfectly and fast.

It would be quite nice to reproduce this printer and make it open source... If someone has an idea (and time)...

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  • \$\begingroup\$ ...The guy use 405 nm laser diodes @ 90 mA. I may be wrong but these parts look close to the requirement : digikey.com/product-detail/en/D405-120/38-1035-ND/3438595 (405 nm, 150 mA => 90 USD) digikey.com/product-detail/en/D405-20/38-1034-ND/3178450 (405 nm, 75 mA => 45 USD) \$\endgroup\$
    – asm8086
    Nov 5, 2014 at 9:42
  • \$\begingroup\$ Can you add a bit of a summary of what the YouTube videos are about to make the answer a bit more self-contained in case the videos are ever removed? \$\endgroup\$
    – PeterJ
    Nov 5, 2014 at 12:31
  • \$\begingroup\$ The video shows a laser that removes the paint, the pcb is in acid bath at 5th minute of the video. yet it s exactly what I want. \$\endgroup\$
    – dvdmn
    Dec 7, 2014 at 3:27

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