Comments on: Laser etching printed circuit boards

By: Dave

Dave — Thu, 24 Sep 2009 05:43:18 +0000

Very interesting. I may try this for SMT stencils. I usually send PCB’s out, but I’ve been looking for a good solution for cheap solder paste stencils.

I have an old and crotchety Epilog Summit that still does 10W or so. I’ve tried making stencils in drafting mylar, but the power setting is just too touchy, there is a fine line between getting a clean cut and getting goo.

The best material I’ve found so far is 17lb drafting velum, which makes a decent 2 or 3 use stencil. 0.8mm lead pitch TQFPs are almost doable but not reliable, and I’ve not had good luck with anything finer pitch. Works great for SO parts and 0603, etc.

So I’m thinking I’ll try your trick, but use 0.003″ brass sheet metal. That should make a decent stencil.

-dave

By: Nabeel

Nabeel — Sat, 06 Jun 2009 12:27:50 +0000

0013 400019331 000421 EACH 1
BOARD , PRINTED CIRCUIT: FUNCTION: UV
EPROM; ADDITIONAL DATA: UV
EPROM,M27C1001-10F1 128KX8BI 1MB, TS
STOCK NO. 169-3439, MFR: ST
ELECTRONICS, MFR PART NUMBER:
M27C1001-10F1 FDIP32W, USED FOR MARK V
CARDS. FOR GE GAS TURBINE INSTALLED IN
ASIR POWER STATION. GENERAL
ELECTRIC/DIELEKTROL/LENTRONICS P/N#
M27C1001-10F1 ST ELECTRONIC P/N#
M27C1001-10F1 APPLICATION:
MFR NAME:REFER TO MFR ON LINE 500
MFR P/N :M27C1001-10F1
Bid Number Bid Send Bid Close
Q090690252415L 02/06/2009 16/06/2009

0005 203647889 000260 EACH 1
BOARD , PRINTED CIRCUIT: FUNCTION:
EARTH FAULT DETECTION; ADDITIONAL DATA:
APPLIC:FOR BATTERY CHARGER; TYPE:
125TPR100; CODE: A6873-010P0T1; VOLTAGE
RATING : 125 VDC; CURRENT RATING : 100
A; SAFT NIFE P/N# B00625400300
Bid Number Bid Send Bid Close
Q090589781255L 02/06/2009 10/06/2009

0007 203647889 000260 EACH 1
BOARD , PRINTED CIRCUIT: FUNCTION:
EARTH FAULT DETECTION; ADDITIONAL DATA:
APPLIC:FOR BATTERY CHARGER; TYPE:
125TPR100; CODE: A6873-010P0T1; VOLTAGE
RATING : 125 VDC; CURRENT RATING : 100
A; SAFT NIFE P/N# B00625400300
Bid Number Bid Send Bid Close
Q090589781255L 02/06/2009 10/06/2009

By: Jack Freeman

Jack Freeman — Fri, 29 May 2009 18:21:12 +0000

Pretty cool!

Check out this place, http://www.etchingpros.com, they do laser etching – on marble slabs up to 4 x 8 feet! Now that’s a serious laser!

By: Kevin

Kevin — Thu, 30 Oct 2008 16:04:45 +0000

Brandon- I also run a 45w Epilog and there is a setting in the driver that lets you do bottom-up engraving. That prevents the redeposit as the laser starts at the bottom of the board and works towards the top with the airflow direction instead of against it. I don’t know which other lasers offer that in the driver though. Makes a huge difference in engraving two-colored plastics.

By: ray

ray — Mon, 11 Aug 2008 10:23:04 +0000

as for garrett’s response, we also did screen printing before we lasered the boards. i think (i’m not sure, i wasn’t involved wit h this process) they printed out the patterns on transparency’s and transfered them onto the light sensitive green stuff (emulsion? it’s been awhile) but that wasn’t very good for tight boards. some of the paint would smear over and connect tracks. so in the end we did it all with lasers as part of our high school tech-ed class.

By: ray

ray — Mon, 11 Aug 2008 09:29:31 +0000

we did this in high school in 2000, we used a thick blue paint from our graphics department, and etched off the paint using a negative of the circuit with our wood shop department’s etching laser.

By: garrett

garrett — Tue, 05 Aug 2008 11:41:41 +0000

@7: the magical chemical i'm using is 99% rubbing alcohol from safeway on a paper towel. It takes off the residue without destroying the resist pattern. Oh, and the paint I'm using is Rust-Oleum "Painter's Touch" flat black from Home Depot. I go ahead and wipe the copper clad with alcohol before spraying it, though I don't know if it really matters. I'm using a 45 watt Epilog laser at 100 speed and 50% power, 600DPI. That's a little more power than they recommend for painted brass, I wanted to make sure the paint was really vaporized off the surface.

The main thing I like about this method is the reliability. Whatever you put in your PCB absolutely will appear in your resist pattern. Press-n-peel or laser toner transfer, you may not get everything down. With toner transfer on magazine paper, you even have to scrub all the fibers out of the ink. Sometimes I'd spend 15 minutes carefully scrubbing a board and then finally a few IC pads would fall off.

Getting the pattern onto the board requires one overnight drying step, and then 5 minutes laser time, but the pattern will absolutely make it onto the PCB and then very little preparation before etching.

I'm going to do some more experiments; double-sided boards, spraying paint on an etched board and then lasering off the pads to make soldermask, I even have an idea for silkscreen. Lots of fun....

By: andre

andre — Mon, 04 Aug 2008 22:17:37 +0000

re. laser activation of resist:- see my article on using an HD-DVD laser diode to expose resist :)

-A

By: Tyson

Tyson — Mon, 04 Aug 2008 21:09:07 +0000

Maybe the laser could activate the resist on a photosensitive board? Usually that photoresist is UV sensitive, and I don’t imagine the epilog uses a UV laser, but maybe you could experiment with longer exposures to the laser. You’ll want to keep your environment otherwise dark when you’re doing this, because room lighting will eventually expose the whole board.

I found photoresist to not be difficult to expose; when I used it, I used a household compact fluorescent light bulb, and it only took a few minutes to fully expose the board.

By: Brandon Kinman

Brandon Kinman — Mon, 04 Aug 2008 21:00:53 +0000

So, I have done this with a laser cutter, and am finding that the flat black spray paint that I am using simply is not good enough. When it is ablated by the laser, it has a tendency to redeposit on the copper surface, and must then be removed using some chemical that also has a tendency to remove the paint which you don't want gone.

Unless I find something better than flat black spray paint, I am convinced that the PressNPeel method is easier.

The upside to this technique is that you are able to create smaller features with the laser cutter than you can with the PressNPeel technique.

By: garrett

garrett — Mon, 04 Aug 2008 02:15:25 +0000

Yeah, the Epilogs can’t burn away copper. Also, I found the flat black spray paint to be as close to ideal as I can imagine. You could see the pixel corners from the 600DPI file I used, even higher resolution is possible. Maybe I just happened onto some paint that works especially well.

By: K.

K. — Mon, 04 Aug 2008 02:00:42 +0000

you can do it directly, you just need to crank up the power. LPKF makes laser systems that do just that: http://www.lpkfusa.com/protomat/pl_s.htm
The catch is that the systems cost 150k+

By: James

James — Mon, 04 Aug 2008 01:59:02 +0000

or maybe wax which you could remove in boiling water?

By: barry99705

barry99705 — Mon, 04 Aug 2008 01:28:54 +0000

I’m pretty sure you can just “etch” the photo negative right on the board. The laser will vaporize the copper. You’ll need to play around with the power settings though, and it’s probably not the fastest way to do things. Hell you could probably raster cut the edges if you want to do multiples.

By: SuperJdynamite

SuperJdynamite — Mon, 04 Aug 2008 01:06:09 +0000

Maybe using layout fluid would work better. It’s designed to put a thin even film on metal which you then scribe into to mark cut lines. It typically has a complementing remover liquid that takes it off.

IF it stands up to the etch process I think it would be ideal.