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Conundrum

Sat Jun 21 2008, 11:11AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

Hi all.

I had a discussion with someone a while back about whether the NUV light from a Blu-ray or HD-DVD laser diode would be powerful enough to "burn" the photosensitive coating on a piece of FR-4 PCB.

It works!!!! just tried it now and I can see patches of the green photoresist have visibly changed reflectivity where I "drew" on them with my focussed HD-DVD laser running at about 37.5mA (parallel 2K4 resistor means I am actually feeding it 39mA) with about a 0.2 second exposure.

Setup is the diode with the Blu-ray lens placed directly on top with about a 0.1mm gap, encased in some low melting point alloy with connections and resistor shielded by epoxy.
Currently running from LM317T with 39 ohm and 180 ohms in parallel from Adj to Out.
(memo to self:- check output current BEFORE hooking up diode!!)

Next step will be to set up a modified "print" head using a stepper and board feeder.

I would expect a Blu-ray laser to work more effectively however the one I removed from the broken PS3 laser module was a lot more sensitive than expected and suffered COD during testing (and also had pre-existing damage showing up as "lines" on the uncollimated output.

This laser was removed from a surplus HD-DVD Xbox 360 drive, which there seem to be quite a few of (I wonder why haha) and these are the cheapest source other than PS3 lasers. I got mine for Â£32 on Ebay with mains adaptor and remote, plus you can use the gutted drive to play DVDs as the red laser diode is separate from the HD diode.

regards, -Ae

Finn Hammer

Sat Jun 21 2008, 02:55PM

Registered Member #205 Joined: Sat Feb 18 2006, 11:59AM
Location: SkÃ¸rping, Denmark
Posts: 741

Conundrum wrote ...

Next step will be to set up a modified "print" head using a stepper and board feeder.

This could become something big, but wouldn`t the next logical step be to dump the PCB in drain cleaner to see if it has developed at all?

Chers, Finn Hammer

Hon1nbo

Sat Jun 21 2008, 04:05PM

Registered Member #902 Joined: Sun Jul 15 2007, 08:17PM
Location: Pacific Northwest USA
Posts: 1042

very good idea, as those diodes emit quite a bit of UV... I would love to see a full homemade PCB machine... I am sure this would be a must try project...

...

Sat Jun 21 2008, 05:14PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

I would try looking for bare diodes on ebay, I got a 130mw 405nm diode for about $60 (and there are still some left for sale)

In any case, I hope you can make this idea work!

Conundrum

Sat Jun 21 2008, 07:55PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

Hmm. I assume that by "drain cleaner" you mean something based on sodium hydroxide.

Catch is, I can't get that over here. I can get washing soda or caustic soda, but a solution of the former did nothing.

Tried Jessops but no go (though they did have some acetic acid "stop" bath bottles)

Any ideas?
BTW it looks like I may be getting another BLU-ray diode to play with as this new one still won't read disks due to some sort of alignment issue. I am loathe to send it back so as soon as the new deck arrives this one is getting modded :)

Finn Hammer

Sat Jun 21 2008, 09:58PM

Registered Member #205 Joined: Sat Feb 18 2006, 11:59AM
Location: SkÃ¸rping, Denmark
Posts: 741

Conundrum wrote ...

Hmm. I assume that by "drain cleaner" you mean something based on sodium hydroxide.

That`s right, but the main point was that I thought it would be a good idea to develop this first test piece
before building a whole cnc machine.

Cheers, Finn Hammer

Experimentonomen

Sun Jun 22 2008, 09:26AM

Registered Member #941 Joined: Sun Aug 05 2007, 10:09AM
Location: in a swedish junk pile
Posts: 497

Why not just mod a laser printer as in removing the drum and redo the mechanics to accomodate a flat board, then replace the laser with one with the right wavelenght ?

Conundrum

Sun Jun 22 2008, 10:45AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

Interesting idea, but you'd have to replace the optics as the blue diode is reallly hard to focus. I had to work for nearly an hour making incremental adjustments on the epoxy lens mount just to get a reasonably good spot geometry.

OTOH, if you gut a Bluray module you can remove that little microscopic circular grating under the lens, put this above the laser diode (if need be leave the lens intact but trim its mountings) and the resultant beam should be a lot "cleaner" but you'll lose some output.

I set the focus for about 8cm but obviously this can be shortened.

see here

This guy is selling brand new Blu-ray diodes
hope this helps, -A

...

Sun Jun 22 2008, 06:19PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

but for the same price this guy is selling 150mw ones

BTW, for focusing I have had very good luck using the cheepo diode colminators (like

you just unscrew the end a little to correct the focus

GeordieBoy

Sun Jun 22 2008, 07:53PM

Registered Member #1232 Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881

Wouldn't a focused laser diode write in such thin lines (like 10 micron spot size or smaller?) that exposing photoresist on a PCB using a focused laser diode would take forever?

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