Laser Etching PCB Artwork - I

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Laser Etching PCB Artwork - I

Post by parkview » Mon Sep 19, 2016 1:58 pm

Recently there was an interesting Hack-A-Day blog post with someone building a specialised X-Y motorised PCB plotter platform: It's a great series on the iterative project build.

Initially I wondered if I could add a pen onto my laser cutter, but Stephen suggested I try laser etching PCB's directly. My first go was laser etching my version of Stephens KiCAD Battery charger board:
SW Makers Battery board.jpg
SW Makers Battery board.jpg (48.66 KiB) Viewed 1847 times

Above, some of the tracks connecting the central IC are down to 9.8mil (0.25mm). They didn't come out too well, so i thought it would be time to do a track size calibration test PCB. This is the simple circuit I used:
cal_Test.2.jpg (63.3 KiB) Viewed 1847 times

I then laser etched the above circuit 6 times using different speeds and laser power. Here is the over all board (first 5 and some other tests) before it was cleaned:
overall_view_pre-clean_sml.jpg (56.56 KiB) Viewed 1847 times

and the same board once it's been cleaned with Methylated Spirits:
overall_view_post_clean_sml.jpg (71.91 KiB) Viewed 1847 times

They kind of all look the same, so lets zoom in to view just a few of the 15mil (0.38mm) tracks.

Here is a 50mm/sec at 40% power ~ 9mA:
15m-50m_50mm-at-40percent_15m.jpg (211.27 KiB) Viewed 1847 times

100mm/sec at 20% power - 4.5mA:
15m-50m_100mm-at-20percent_15m.jpg (302.56 KiB) Viewed 1847 times

just as a reference, here is the same speed and power, but of a horizontal etch:
15m-50m_100mm-at-20percent_15m_hor.jpg (256.08 KiB) Viewed 1847 times

just to see how it went I upped the speed to 200mm/sec at 40% power. You can see the individual laser cuts as it swung back and forth:
15m-50m_200mm-at-40percent_15m.jpg (405.32 KiB) Viewed 1847 times

The best seemed to be 100mm/Sec at 20% power. This took 2min. 45 Sec. to etch the paint off a 33mm x 59mm area:
15m-50m_100mm-at-20percent.jpg (2.44 MiB) Viewed 1847 times

I noticed that one trial of 50mm/sec at 40% power the laser would actually burn up the laser dust, giving a sparkler effect as it progressed:
laser sparkles.jpg
laser sparkles.jpg (39.25 KiB) Viewed 1847 times
Last edited by parkview on Thu Sep 22, 2016 10:56 pm, edited 3 times in total.

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Re: Laser Etching PCB Artwork - II

Post by parkview » Mon Sep 19, 2016 2:05 pm

Lastly, I did do another trial going down to 9.8m (0.25mm) tracks, but it seemed to be below what could be reliably etched. These where done at 50mm/sec at 40%:

Vertical etches:
9.8m at 50mm-40percent_ver.jpg
9.8m at 50mm-40percent_ver.jpg (41.64 KiB) Viewed 1846 times

9.8m at 50mm-40percent_hor.jpg
9.8m at 50mm-40percent_hor.jpg (38.9 KiB) Viewed 1846 times

Overall board - 85mm x 65mm, took 18m 26s to etch at 50mm/sec:
Post-Cleaning Calibration test 9.8m to 60m.sml.jpg
Post-Cleaning Calibration test 9.8m to 60m.sml.jpg (33.56 KiB) Viewed 1846 times

I tried two kinds of flat back paint, with this one giving excellent strength and finish. The copper board was sprayed with three light coats, about 2min apart and then dried for 30min before laser etching:
Flat Black - Spray Paint.sml.jpg
Flat Black - Spray Paint.sml.jpg (73.92 KiB) Viewed 1846 times

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Re: Laser Etching PCB Artwork - III

Post by parkview » Wed Sep 21, 2016 10:43 pm

OK, now that I have a masked PCB, the next step is to etch away the unwanted copper.

First off, I lasered another two images, in an area that I could easily cut out:

calibration test.1.jpg
calibration test.1.jpg (54.16 KiB) Viewed 1842 times

SW Makers Turtorial Battery Charger Board:
calibration test.2.jpg
calibration test.2.jpg (83.26 KiB) Viewed 1842 times

Here they are all cleaned up ready for etching:
calibration test.cleaned.jpg
calibration test.cleaned.jpg (85.61 KiB) Viewed 1842 times

I used a Bunnings Hydrochloric Acid (?%) and hydrogen peroxide (3%) in a 1:2 ratio and rocked the bath and brushed the board gently with a sponge every now and then. You can see that the RH board is nearly finished:
etching boards.jpg
etching boards.jpg (44.46 KiB) Viewed 1842 times

They turned out pretty well for a first go:

Track Calibration board:
calibration test.1.etched.jpg
calibration test.1.etched.jpg (43.05 KiB) Viewed 1842 times

and the Battery charger board:
calibration test.2.etched.jpg
calibration test.2.etched.jpg (69.82 KiB) Viewed 1842 times

Well, that looks ok, so lets zoom in and have a look at the fine 9.8mil and 15mil interconnects to the central chip:

First off, here is the lasered board before cleaning the dust off the board:
closeup_pre-cleaned.jpg (25.67 KiB) Viewed 1842 times

Then the same section after cleaning:
closeup_cleaned.jpg (75.73 KiB) Viewed 1842 times

and after etching:
closeup_etched.jpg (20.11 KiB) Viewed 1842 times

And just for stamps, lets have a close look at the 15mil section of the calibration board:
calibration test.1.etched.closeup.jpg
calibration test.1.etched.closeup.jpg (72.38 KiB) Viewed 1842 times

So, what could be done better?

1) If you compare the top photo of the freshly lasered board, you can see that all the resistor outlines are present, but not after the dust has been cleaned off the board (third photo). Obviously I have to be a lot more gentler in this cleaning phase. Next time I will try some compressed air and using a fine brush to see if that helps. This would also help with the 9.8mil tracks as well. You can also see that one of the fine alignment cross hairs has been rubbed away on the LH side, but it didn't look that robust to start with.

2) The etching was a reasonable 10 min or so. Unfortunately I didn't time the process, but it didn't seem unreasonably long. The Battery charger board could have been left in the etchant solution for another 60 seconds or so, as there is still a bit of copper left around some of the central fine tracks. These will now have to be carefully dremaled out.

3) I have had a go at roughly measuring the tracks and they seem to be about right. Interesting that in the top RH corner of the bottom photo you can see that even see the zig-zag of the laser etching out the paint mask has been transferred onto the copper - just like it should.

4) this is a handy fast technique - if you have a laser. In under 15min, you can laser a board and have it etched. Very handy for prototyping a PCB layout before sending off to have a board professionally created.

5) I cleaned up the previous lasering tests on rest of the PCB board with acetone. Then re-sprayed the sections with a few fresh coats of paint. This will keep the PCB from oxidising and fresh for when I need it next.

I can see some of my previous one off project vero boards will be re-created as a PCB. :)

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Re: Laser Etching PCB Artwork - IV

Post by parkview » Thu Sep 22, 2016 10:47 pm

Well, I had to give it another go to see what thinner tracks might look like. I also wanted to have another go at comparing vertical lasering vs. horizontal lasering. This time the board's tracks were set to: 8 (0.2mm), 9 (0.23mm), 10 (0.25mm), 11 (0.29mm) and 12mil (0.3mm):
calibration.3.sml.jpg (40.28 KiB) Viewed 1840 times

Although the above board artwork looks fine, the laser cutter software can only import JPG files, not SVG files directly. To do this, I import a much larger JPG file and then manually shrink the image down to a known object size. In the above art work, I was using 10mm through hole resistors, so I made sure there was 10mm between the pads.

One thing I suspected from the previous days etching, was that during this process pixel artefacts occur during the shrinking process. The above art work looks perfect, but it's very clear that some thing is going on. The art work was brought in vertically and shrunk down. After lasering I then rotated it 90 deg and did another board. You can see that there is a large difference in track sizes, for example compare the top 10, 11 tracks on the vertical and horizontal boards:

Vertical laser etched:
calibration.3.ver.jpg (30.26 KiB) Viewed 1840 times

Vertical etched and cleaned:
calibration.3.ver.etched.jpg (26.35 KiB) Viewed 1840 times

Horizontal laser etched:
calibration.3.hor.jpg (31.38 KiB) Viewed 1840 times

Horizontal etched and cleaned:
calibration.3.hor.etched.jpg (27.43 KiB) Viewed 1840 times

When I closely look at the RDWorks laser cutting software, I can see that some of the lines are shadowed in grey - from the aliasing. This is less noticeable on thicker tracks.

I wont bore you with a mired of photos, but this time I lightly cleaned the horizontal board and didn't clean the vertical board at all. The former was etched in around 22 min (how time flies when your having fun) and the non-cleaned board took around 37 minutes and it took a lot more wiping down in solution. Eventually the remaining paint fell off. It's hard to see, but the no-cleaning board came out the best, but perhaps some of that might be due to a cleaner etch. I pulled the partially cleaned board out a bit too early.

So how did the thin tracks go? Apart from the art work issues, the PCB etching came up reasonably well. Have a look at a close up of the 8mil section:
calibration.3.hor.etched.closeup.jpg (40.27 KiB) Viewed 1840 times

I am taking the bottom track to be 8mil. The top one might be 6 or 7 mil. I don't currently have my microscope reference sheet, so I can't correctly measure the thickness at the moment. There is continuity on the top track, but it doesn't look to be a reliable line thickness.

Just out of interest, I think by default the component outlines are around 5.5mil or 0.145mm thick, so no wonder they are so easy to wipe off, or over etch into oblivion.

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Re: Laser Etching PCB Artwork - I

Post by seaton » Fri Sep 23, 2016 12:11 am

Looking good!

Definitely works at the bigger sizes no problems. I think the finer SMD is a challenge no mater what even on my CNC

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Re: Laser Etching PCB Artwork - I

Post by Jubbp » Thu Oct 06, 2016 12:26 am

This is just so cool. Great work Paul!!

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Re: Laser Etching PCB Artwork - I

Post by BeJay » Sun Oct 16, 2016 9:16 pm

I have cnc'ed my first PCB, and it was really good, but nothing like the resolution you have here. I'm going to convert my old hadron3D printer into a PCB cnc I think. Great work as always Paul!

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