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HD-DVD PCB maker

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LAN_403

EEYORE

Mon Jun 23 2008, 03:25AM

Registered Member #99 Joined: Thu Feb 09 2006, 06:10PM
Location: florida, usa
Posts: 637

GeordieBoy wrote ...

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?

You could just bring the laser out of focus a little...Right?
Matt

GeordieBoy

Mon Jun 23 2008, 09:57AM

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

> You could just bring the laser out of focus a little...Right?

...but that will presumably decrease the power density meaning it will take much longer to expose?

Conundrum

Mon Jun 23 2008, 07:06PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059

will have to investigate this. I did obtain some Na(OH)2 so can now develop the PCB. Unfortunately it looks like one of my chemicals mullered up the photoresist but thats no biggie as there's still enough to expose it again.

The power density is high enough that at 0.1mm focus it will still expose a fairly large area (0.3mm diameter when I tried it) so ironically the problem is going to be avoiding over exposure.

Update:- It works, just finished the (slow as molasses) etching now. See below for my ingenious Macgyver-style PCB etch heater..

Update 2:- Have ordered some spray-on PCB photoreactive coating, will update you as to how well this works with the same diode and/or UV LED array (30s exposure time)

-A
"Bother" said Pooh, as the warp nacelle fell off...

Conundrum

Tue Jul 08 2008, 06:26PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059

Update:- I discovered a slight problem with the Ebay purchased photosensitive material as it is the "blue" type inferior dye. It does work but is about an order of magnitude less sensitive.

I suspect that rapidly spinning the PCB during spraying will get around this problem (google "spin coating") and will try this next. In the meantime, perhaps an additional modification would be to irradiate the vicinity of the focus area with UV light from conventional NUV LED's to presensitise the PCB and let the laser do its work more quickly.

Side effects would include a chance of burn-through, but the increase in throughput would be worth it.

Please advise. I can't believe I'm the only person to be working on this...
regards, A

Carbon_Rod

Wed Jul 09 2008, 11:05PM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

For thin coats slow dry at a 60' angle.

note if any droplets appear there was too much emulsion applied.

Photo plotters were around for many years, but became much less popular in the late 90's.

aonomus

Thu Jul 10 2008, 01:43AM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

You got posted on Hack A Day I think....

Conundrum

Sun Aug 10 2008, 01:38PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059

*This* is what happens when you use a proper 150mW Blu-ray burner diode instead of a wimpy HD-DVD read laser.

Obviously you ABSOLUTELY MUST USE safety goggles!!!!!!!! I used one of those gas welding goggles which does work but would strongly recommend the correct equipment.

(end of safety rant)

Diode is being run at approx. 95.6mA which is well within its safe limits. The seller says he has run them up to 120mA but for test purposes this is fine.

Safety circuits include:- parallel 1K resistor and 0.1uF capacitor, input smoothing and zener, so that in the unlikely event of a regulator problem or other anomaly the diode should survive.

As you can see, I've encased the diode in low melt 95c alloy and mounted the lens the same way, this is not ideal but it does at least allow reasonable run times without risking thermal runaway.
I estimate heat being generated is around 0.7W at 95mA
The assembly is mounted on a surplus heat pipe from a broken PC motherboard, and fixed to the HP LJ module with epoxy.

I had to remove the two beam shaping lenses as it turned out they defocussed and absorbed the beam too much, without them the dot looks much sharper and the beam is nice and round with few artifacts.

UPDATE 2:- Spin coating the PCB with resist works well, you need to do this in low light however or your hard work will be wasted. I
used a modified PC PSU fan motor and glued the PCB to it, then started from the inside edge and worked outwards at about 1cm/sec then let it dry. The results speak for themselves :)

1218385702 96 FT0 Spincoat

Here are some pics.

Conundrum

Fri Jan 02 2009, 05:06PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059

Hi..

I have mounted the scan module onto a spare scanner cover, so it now has stepper and CDROM drives as the X and Y grids.

The scanning area is approx 2" across (with modified laptop drive unit) and it also etches through the glass thereby preventing the annoying PCB alignment problems.

Observe.

-A

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