Using a paint pen on a PCB? - Page 1
Forum section: electronics / general

author: Piquan
author_rank: Newbie
timestamp: November 11, 2018, 12:00:09 am
content: I'm going to be ordering a small set of PCBs from Macrofab. The PCBs are meant to be decorative as well as functional, and to get a personal touch, I'd like to sign them (they're for friends and family). I've made an area clear of vias, holes and components (there are traces under the soldermask), but I don't know if a paint pen will work on top of a solder mask.I'm thinking of using a metallic silver oil-based paint pen (e.g.,https://www.sharpie.com/markers/art/oil-based-paint?sku=SHOilBasedPaintSilverFine). This would be on a green LPI soldermask (R-500 GHB).Has anybody tried this, or other methods of writing on soldermasks? I really want this to be in light-on-green, so I don't want to put a bunch of silkscreen down to write on or something like that, and I want it to be a bit more personal than just putting my signature on the silkscreen.

author: oPossum
author_rank: Super Contributor
timestamp: November 11, 2018, 12:09:47 am
content: Ordinary black permanent markers work on solder mask. When I worked as a tech we would initial the PCB with a sharpie after doing QC. I don't think you will have a problem with a paint pen.

author: mrpackethead
author_rank: Super Contributor
timestamp: November 11, 2018, 02:42:56 am
content: what are you making?

author: Piquan
author_rank: Newbie
timestamp: November 11, 2018, 08:28:46 am
content: Quote from: mrpackethead on November 11, 2018, 02:42:56 amThis is a Christmas decoration. It's a PCB in the shape of a Christmas tree, with blinking LEDs scattered around it.Some of the "ornaments" on the tree are large copper pads, which act as capacitive touch sensors, to allow the user to adjust the brightness and select the blink pattern. The cap sensors and logic are managed by an ATtiny84A, and the LEDs are driven by a TLC5947.Power is from a USB connector. I originally planned to make this an ornament that would hang from a tree with LiPo power, but had a hard time managing safety issues with bare copper + LiPo + year-long storage between use + random other ornaments and debris, all hanging from a dead tree. So I switched to a decoration that could sit on a shelf or desk, held upright by a 3d printed base that looks like a stack of presents.Since this is a decoration, this is very much a case of "function follows form". Relevant to this thread, the back soldermask says (in large, friendly letters) "Merry Christmas 2018" / "Love Always," followed by a space for my signature in silver ink pen. Since I didn't want the metal-infused ink to short something (or add capacitance to my sensor lines), I cleared out the relevant space of vias.All this is inspired by a Modern Electronics article I read as a kid in the 80s. That version used a 555, a counter (7490, I think, maybe a 7493), and a demultiplexer (74138?) along with some diode-ORs to sequence the flashing LEDs. It used things like 20% carbon resistors, because they looked pretty as decorations. (At least, more so than the more-common carbon composition resistors of the day.) I decided to rebuild it with modern technology as a decoration to give to friends and family.The whole thing is open source. I'm still fiddling with it, but I've got some of my work (schematic+PCB in KiCad, and firmware) athttps://github.com/piquan/christmas-tree

author: djacobow
author_rank: Super Contributor
timestamp: November 12, 2018, 11:51:44 pm
content: Quote from: Piquan on November 11, 2018, 08:28:46 amSo I did something much like this last year with a Hanukkah menorah. I actually personalized the menorah PCB itself with a mixture of silkscreen and solder mask. I put in a ground flood everywhere, and so where I had written a message in mask, I got a nice silver lettering, which works well for Hanukkah (blue board, silver writing) Actually, PCB houses have much better control on solder mask than on silkscreen, so everything written that way looks sharper and better than had it been silk.This year I re-ran that PCB, but without a personal message, and I'm selling them on Tindie and Amazon:https://www.tindie.com/stores/djacobow/

author: Piquan
author_rank: Newbie
timestamp: November 13, 2018, 08:06:26 am
content: Quote from: djacobow on November 12, 2018, 11:51:44 pmThat sounds like a great project! I'm glad to hear it worked well enough to make a product; best of luck with it!I avoided a ground flood, since it can lower capacitive touch sensitivity. In my experiments, though, I found that I get plenty of sensitivity (at least at the workbench), so if I had time to make a few more board revs, I would try it with a ground plane.If I understand you right, you used HASL plating for your PCB; is that right? I'm using ENIG, which would also look nice that way, although I was hoping for a more silver color for this bit of the design. Hmmm, maybe I could cut the solder paste stencil in some spots to get some silver.It looks like you did this for the "חנוכה" / "Hanukkah" label at the bottom; is that right? (It's hard to tell; in the picture with the white background, the label looks very similar to the solder mask, although the difference is more distinct in the picture with the table.)

author: brabus
author_rank: Frequent Contributor
timestamp: November 13, 2018, 08:10:58 am
content: The only marker that works for me:Staedtler Lumocolor Permanent. I personally use the fine (F) tip.Still have boards with markings from 10 years ago, as good as they were just signed.

author: bd139
author_rank: Super Contributor
timestamp: November 13, 2018, 09:30:27 am
content: Quote from: brabus on November 13, 2018, 08:10:58 amAgree with this. Those pens are more than excellent.

author: djacobow
author_rank: Super Contributor
timestamp: November 13, 2018, 03:42:11 pm
content: Quote from: Piquan on November 13, 2018, 08:06:26 amThat's right, I used HASL. I think ENIG is generally great, but I wanted the silver color. Yes, I used it to spell "חנוכה" / "Hanukkah" on the front. In the original version there was also the year. On the back I used silk, but in the original version "with love from XXXX" on the back also in mask.Capacitive touch is something I should have looked into. I have a good supply of small tactile switches at very low cost, but free is always better for this sort of thing.

author: 1276-2449-1-ND
author_rank: Regular Contributor
timestamp: November 30, 2018, 01:30:58 pm
content: I had problems with the metallic ink pens smudging over time. Now I use paint pens (the kind that rattle), but white is kinda thin when it writes (but black is excellent.) The paint pens also don't come off with IPA.