09/26/2019 at 15:59 •
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...Read more »
09/09/2019 at 16:43 •
Arc Badge was born out of failure. Post DEF CON or really any major conference where a lot of creative people are in the same place, you can't help but leave with a dozen sparks of inspiration. Some of those sparks never go beyond the initial idea phase for one reason or another but some sparks grow into a raging fire that will hopefully be used to forge something wonderful. Post DC26 I had "a great idea for a badge". It featured multiple PCBs, lights, sounds, and had a really popular theme. Unfortunately I barely knew how to light up an LED so I had a lot to learn to make it happen and well basically life got in the way and next thing I knew it was almost spring 2019.
The project wasn't where I needed it to be so I shelved it. I decided instead to focus on making a Shitty Add-on Totem for the SAOs I was designing for DC27. I thought it'd be really cool to have a Totem shaped like an Arc Reactor and even cooler if it lit up and could change colors so eventually that idea evolved into Arc Badge.
Here were my design goals for Arc Badge:
- Do Double Duty as a Indie Badge & a Costume Prop
- Be instantly recognizable to anyone familiar with the MCU Iron Man
- Accommodate Two SAOs
- Make the Lanyard easy to Connect & not interfere with the SAOs attached to the Badge
These first two goals were born out of what I liked to do before I started making badges: Making Prop Replicas. The third goal is what made me decide to go with the Avengers Infinity War/Endgame style Arc Reactor. The two "Ears" at the top of the overall triangle shape provided a natural place to have SAO headers protrude from. The final goal was born out of lessons learned from DC26. We had already made changes to the SAO standard so that it was a keyed 2x3 vs a regular 2x2 so we were going to have better overall stability but sometimes SAOs popped off because the lanyard on the badge that was hosting them would knock them off.
Lanyard Placement is very important.
A great deal of thought was put into how the lanyard would connect and where it would be placed. From the picture above you might notice that the two yellow dots indicating where screws would go are not in the correct place. This drawing is from an early concept. I knew that Arc Badge was going to be made up of 3 layers: The top "Art" board, a 3D Printed Spacer, and the bottom board where all of the electronics would actually be.
So working with that I decided the best place to put the lanyard would be on the standoffs that the top board attached to. This greatly influenced how the 3D Printed Spacer would be designed and is actually why it was ultimately 3D Printed vs being laser cut out of acrylic.
For one I could 3D Print them myself on my Prusa MK3, second I could design the model to have cut outs for the stand off so a Lanyard could easily access it and connect to it. I designed the spacers in Inkscape and then pulled them into TinkerCAD to extrude them into 3D and then to cut out the areas where I needed the lanyards to have access to the stand offs. It was important to design the gap to be large enough for the lobster claw to easily clip on and to have some room to move as necessary.
There were about 1/2 a dozen prototypes of these spacers. You may have noticed from the two pictures above that I started by printing them in halves. This was so that I could print out as many spacers as possible at the same time. I ultimately abandoned the two part design because sometimes where the two parts met they would bow out a little from between the two PCBs. Structurally it wasn't a big deal but aesthetically...Read more »
04/11/2019 at 03:15 •
So if you've seen damn near anything I've done for the last 18 months then you've seen examples of using Reverse Mount LEDs and also manually mounting LEDs upside down.
I like shining LEDs through PCBs, it's a great lighting effect and it isn't as harsh a light as you get from having the LEDs on the top side of the board. However there are a handful of draw backs to using them.
Reverse Gullwing LEDs:
- They're expensive.
- "Reverse Gullwing" LEDs are just expensive. Even quantities of 1,000s RGB Reverse Gullwing LEDs are over $0.40/ea as compared to $0.02-0.04 you typically see with a comparable size LED.
- They're exceedingly rare.
- This point is pretty obvious based on the price but there are only about 3 manufactures that make LEDs in this package and only 1 of them makes the RGB variant.
- Minimal light propagation
- If you're putting an LED directly onto the PCB that it's shining through then you only get a circle that is about 9mm in diameter. This varies based on the color, voltage, resistor used etc but in general it's only 9mm and it takes a crap load of LEDs to cover a relatively small area. This only exacerbates the first issue.
Reverse Mounting Normal LEDs:
- Not Pick n' Place Friendly
- Soldering LEDs Upside Down on purpose involves a lot of manual labor and is not solder paste or Pick n' Place friendly, this means it's a solution that does not scale well at all.
- Same Light Propagation Problem as Reverse Gullwing LEDs
So between these two solutions there is the classic "Cheap, Fast, Good, pick two" dilemma. Reverse Gullwings are Expensive, but fast and good. Manually soldering LEDs upside down is Cheap, Slow, but also Good. Now let's look at another solution: Side View LEDs.
Side View LEDs
Side View LEDs are exactly what the name says. They're LEDs that instead of shining up or down they shine at a right angle. Side View LEDs are cheap, pick n' place friendly, and you can get them in every standard LED color including UV and RGB. My initial interest in Side View LEDs came from wanting to use the UV variant on some projects to get that eerie glow you get when UV light is shined onto FR4.
This is an effect I still intend to use on future projects but I also saw the possibility that I could use Side View LEDs in place of Reverse Mounted LEDs. Unfortunately it isn't as simple as just replacing one foot print for another. Side View LEDs were not designed to be used for this purpose, they're designed to, well, shine light at an angle and are typically used as indicator lights in most consumer applications, think something along the lines of status indicator lights on a Laptop. As such there is a tremendous amount of light bleed that you have to control.
The other major issue with using Side View LEDs is that the light that does shine below them isn't as bright as using a Reverse Gullwing or a typical LED mounted upside down. Due to their vary nature the light they output isn't in a circle it's more like a 1/2 Circle or a very wide cone so you have to rethink your designs to take advantage of that as well.
I designed a simple prototyping board so that I could get measurements and figure out how to best work with these LEDs before I put them in a project. I am very glad I did this because despite having seen other examples of Side View LEDs being fantastic drop in solution for back lighting PCBs I instead found it had its own draw backs.
- Uneven Lighting
- So this is similar...
- They're expensive.