Disclaimer: The OSHPark boards pictured were designed by me (TwinkleTwinkie) but were paid for by OSH Park.
OSHPark recently announced their new "After Dark" finish option for their PCB Prototyping service which brings a wonderful new alternative to their traditional Purple Solder Mask & ENIG Copper Finish. "After Dark" brings two major changes to what you normally see from an OSH Park board: Black FR4 and a Clear Solder Mask.
Black FR4 is one of my personal holy grails for creating PCB Art. Although it isn't exactly unobtainium it is typically expensive and only a handful of Fabs have it as an option so as a result is rarely seen, even in #BadgeLife. The only example of it I am aware of is Queercon 13's Blooper Badge.
Blooper's amazing aesthetics is owed in part due to its use of a Clear Solder Mask & Black FR4 substrate. It was so influential that it pushed me over the edge to try out PCB Art and directly inspired the Mr. Robot Badge by @MrRobotBadge the following year.
Thanks to OSHPark's addition of their "After Dark" option this once rare combination is now readily available to anyone, and the best part is it doesn't cost more than their normal option! So to prepare you for making your own "After Dark" PCB Art I've updated my "Pharaoh OSHCat" SAO to show off the new characteristics and capabilities of this new option.
Clear Solder Mask
Working with a clear solder mask isn't really any different than working with an otherwise opaque solder mask. Artistically it gives us two colors: Copper, & Shiny Dark Gray. The copper color comes from the copper that is under the clear solder mask. The Shiny Dark Gray comes from the clear solder mask where there is no copper under it.
With most solder masks the presence of the Solder Mask and the Copper layer just means you get a lighter color of whatever the Solder Mask is, the exceptions being Black & White which are completely opaque. With a Clear Solder mask, as the name implies, you see the copper traces almost as if they didn't have any copper finish or solder mask on them. What this means is we can show off the beauty of the copper without directly exposing it and it also still gives us the use of the Copper Finish, in this case ENIG, to create stark contrasts in color.
The Matte Black comes from the total absence of the Solder Mask & Copper. Its color and "finish" comes from the bare Black FR4 and its matte color and reflectivity is somewhere between a normal Black Solder Mask and a Matte Black Solder Mask. From an art & design perspective this means instead of just one dark shade of black to work with you get two: The shiny dark gray from the presence of the solder mask, and the very dark black from the total absence of both the solder mask and copper layers. This reflectivity could be used in some creative ways when presented in the right lighting conditions.
Other than the obvious black color some other differences between Black FR4 and typical FR4 is that Black FR4 does not light up green under UV Light and because it is black it is completely opaque. Because it is completely opaque you cannot use Black FR4 when you intend to shine light through the board, you will have to have a cut out of the area the light is meant to shine through. A benefit of using hot glue as a light diffuser means that you can still use that technique here and just have the hot glue fill the area you intend to light up.
Silk Screen & Copper Finish
As with typical OSHPark boards the silk screen is still White applied with a High Resolution DLP technique and the Copper Finish is ENIG (Gold). There are no differences between how you would use them on a After Dark board or a normal order.
OSHPark After Dark is Beautiful
I am really excited about the possibilities that readily accessible Black FR4 brings to the world of PCB Art. I'm looking forward to seeing how others take advantage of it, whether it just be a wonderfully complex Prototype board or an intricate Art Board (whose to say both aren't art?).