# Laser diode to remove copper layer from PCB

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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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. –  PeterJ Feb 25 at 2:34
It also likely won't be appreciably faster. –  Ignacio Vazquez-Abrams Feb 25 at 2:42
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. –  DarcyThomas Feb 25 at 8:48
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. –  The Photon Feb 25 at 15:43
This question appears to be off-topic because it is not about electronic design. –  Dave Tweed Feb 26 at 16:47

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).

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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I saw this product and liked it so much but it's price tag (~\$175k) is far beyond hobbyist level. –  dvdnhm Feb 25 at 4:27
Watch the video youtube.com/watch?v=PhH05jNyjCk&list=PL2C566A88EF45284C of that beast in operation. It truly is (electronic) engineering porn. –  markt Feb 25 at 8:37
@markt let's get a NSFWallet tag on that one –  scld Feb 25 at 20:13

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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