I've asked Eurocircuits -- who I've often used to make my circuits for the past couple of years -- if we could collaborate on experimenting with new techniques for PCB manufacturing. To my delight, Luc, Dirk, and their manufacturing team were very welcoming and excited about the idea and were great at producing samples. Their PCB manufacturing expertise is instrumental to the making of boards that are unique but that are also mass-manufacturable and affordable. This is our first experiment.
For a long time now, I've been wanting to create boards that have more than just a single soldermask colour. There is no technical reason that this cannot be done -- it's only a matter of fab willingness, and, of course, cost. The advantage of using soldermask over silkscreen, by the way, is twofold: better resolution, and better registration. (There's also no reason why multiple silkscreen colours can't be done.) Eurocircuits have been at the forefront of innovating in PCB ordering, and have also been offering clients the ability to add graphics to PCBs with their PCB PIXture feature. They add the graphics with soldermask, so they are familiar with a multi-pass soldermask process.
Of course I designed the circuit using our own PCBmodE. The circuit has five warm white LEDs on the bottom side of the board, and an SMD micro-USB connector footprint in the centre of each edge. The idea is that one could choose where to place the USB connector according to the intended use of the board. If it hangs on a wall, it would make sense to populate the connector on the bottom. If it's used as a coaster, side or top placement makes sense. When powered, the light from the LEDs reflects off the surface the board is on and shines through the FR4, gaps in copper, and soldermask.
The visual design is rather arbitrary, but is meant to create engaging structures and also see how well superimposed soldermask layers look like -- then we could have three colours!
OK, enough with the words!
The first variant is 'yellow'. It has black and white soldermask on the top and bottom with yellow silkscreen added on the top.
The second variant is 'red'. This one has white, black, and red soldermask (no silkscreen on the top) with an ENIG finish.
The sharp-eyed would have noticed that the black and white colours are 'dotted' -- this is the technique that Eurocircuits use for PIXture. The main difference from 'yellow', however, is the lack of copper around the text, so light goes through nearly the entire board. This lets the two blue-ish soldermask colours on the back create a very neat and colourful effect.
Which variant if your favourite?
To enclose the board, I've used the same 3mm acrylic pieces -- lovingly made by oomlaut -- that I use for the 'superhero' plaque, but with added spacers for the LEDs and USB connectors. If this plaque becomes a 'thing', an opaque acrylic shim may be a good addition to block the light from seeping through the sides.
Naturally, we love circuits at Boldport and Eurocircuits; this Valentine's Day we really made an effort to show it ;)