The two PCBs for the Revolving light arrived today and I felt both delightful and dismayed. Delighful because JLCPCB came through with the goods which means, they can do this without breaking a sweat. Dismayed because these 8mm discs are really going to be a b1tch to solder and all that. Still, this is going to be a fun weekend…
If you must know, that is my thumb on the left. The idea is to solder the 0805 LEDs upright, like a tombstone. The upper PCB would then join the positive solder pads together. Think of a sandwich where the 0805 LEDs are the filling while the PCBs are the top and bottom bread.
When Inspiration hits
I hate it when an idea suddenly pops up. While I was putting an item into my bag and then turned right to face my table, the though just came in. Having just received the PCBs from JLCPCB moments ago, this sudden thought would mean another order to those PCB makers again. The idea was that instead of using the upper PCB as it is, (a circle), why not have some grooves cut into it. These grooves, in theory, not only aligns but holds the 0805 SMD LEDs in place after being soldered. In theory, soldering to the lower PCB would be easier. Anyway, below are my attempts to materialise my ‘Inspiration’.
The first thing is to create a new PCB layout using InkScape.
Then import the PCB layout or outline into my EaglePCB.
This time, there are a lot of cleaning up to do. EaglePCB interpreted the layout as having double lines. I had to remove the excess which took quite a bit of time.
After that, I had to make sure every ends of single line joins to the next. This can be done by moving and checking each line. This action also helps reveal other abnormalities which needs to be removed as well.
Finally, the new design is complete.
And JLCPCB did not give any errors at all.
So, this idea works but its going to be a lot of work because…
24 Hours later – The Fail
OK, perhaps that Inspiration was more of a forewarning. I soldered the LEDs onto the PCBs and it was quite difficult. The LED’s solder pads are too near to the wire solder pads. When I solder the wire, the LED would come off and vice versa. Once I go that fixed, soldering the top PCB was another issue because I have make sure the LED’s solder pads are aligned. Boy, that is not easy.
This is how I prepare the PCB for soldering. It’s like the Cylon Raider all over again. I like to use 3M’s double-sided PCB as during soldering, their glue lasts slightly longer. Anyway, the PCB pads has been soldered under a layer of rosin flux. I’ll be doing the same to the SMD LEDs. These LEDs are slightly larger than the intended 0805 versions.
So far so good. As I mentioned, these SMD LEDs are slightly different from the 0805 version and the have a dome on top.
This is where the design failed. As I soldered the wires, the heat from the wire’s solder pad transferred to the LED’s solder pad and so, the LEDs fell off. If I soldered the wires first and then the LED, the same thing will happen. This is bad.
This is how it looked like when soldered. I will not power it on since there are a lot of un-soldered pads in there.The second problem is when the upper PCB is placed on top, there is no reliable method to keep them aligned and so, a few LEDs missed their soldering pads.
