And so, after the first inspiration hit a few days ago, I had another. This time, instead of making the sandwich, the idea is to use a single PCB board with the 0805 LEDs soldered in the middle. It is very difficult and time consuming to align the two halves together to match the soldering pads of both PCBS. The introduction of the holes in the PCB is to minimise the wires from moving about in the molten solder when I am dealing with the the 0805 LEDs.
This is the typical dimensions of a 0805 SMD LED which is a standard 2.0mm (L) and 1.25mm (W). Where they differ would be the height of the resin lens and also, the size of the solder pads. But I am banking on the gap between the two solder pads, which averages to about 1.05mm although in the image above, it was 1.20mm. (Diagram courtesy of https://www.tinytronics.nl)
Funnily enough, the test on the right could be the basis of a T-shirt design. Anyway, after taking the 0805’s height dimension in to account, I have redone the 5x gaps using the 1.26mm x 1.10mm rectangle. The PCB design is now double sided where its thickness is enough for the 0805 LED to fit in the middle. The LED is then soldered onto the red rectangle solder pads on both sides. The top (red) would be for the 5 signal wires while the 1x bottom (blue) would be for the power. Their current limiting resistors are already designed on the Main PCB.
Roughly, this is how JLCPCB showed the PCB to be. When I looked at the design, there is no difference. But on closer inspection, the difference is there.
The only difference between the Top (left) and Bottom (right) would be the subtle copper trace from the hole to the solder pad on the left. As for the bottom, the trace is actually a connecting ring near to the centre of the, um, donut.
For the time being, this would be the plan for the Top Revolving Light. I am hoping that this would work but it would take a lot longer to solder and align them. So, yes, I would need to design another ‘jig’ to help expedite the soldering process for production, if it comes to that.
Looking back at the design, if this was to be up-scaled to say, 1:18, it might be possible. The size of the PCB would be about 10.6mm which, maybe, I can use through-hole LEDs instead. And I can even solder a MF microcontroller (top) in there. The only problem would be the polarity protection diode which would be half the size of the chip fighting for space and, I cannot solder the SMD LEDs like what I panned now. Although the advantage is that I do not have to route 6 wires to the PCB, I would have to sacrifice one microcontroller MF chip (top). Compared to the usual SN package (bottom), the cost of the MF package is about 75% more.
