Bottleship Flex 61

The flexible LED matrix board for the Bottleship project.

Updates

May, 2026

I hand-assembled the rest of one of the flexible PCBs, programmed the processor with a test pattern, and stuffed it into the bottle. The processor does work, after a bit of touching up with more flux and a fine soldering iron tip; I was worried about this as the coverlay does not separate the pads so I used as little paste as I could and hoped for the best. Placing the 0402 resistors (470 Ohm for operating at 5V) was also quite difficult. The cheap 0603 warm-white LEDs I got a reel of from AliExpress (4,000 for about £6) don't look significantly different from the more expensive branded ones I had previously got from LCSC. I used solder paste with an advertised melting point of 138°C and a hot air tool at 250°. The board did bend a little but didn't melt or burn, perhaps the caution about high temperatures mostly applies to the transparent FPC material.

A small glass bottle, within is a single round semi-transparent orange flexible circuit board with a concentric pattern of 61 lit up warm white LEDs. The board is held up by a red abd black wire and not yet properly mounted or aligned with the bottle.
One layer, bottled.

April, 2026

The v1 test board has arrived, and I've taken one of the five panels out to experiment with. The tabs worked well and can easily be removed with scissors. The boards however are very flexible, so I'm not too sure if they will stand up to the intended mounting. On the other hand this makes it seem like they could easily be curled up during the installation process.

JLC had asked for confirmation of the order as the distance between pads on the QFN-20 processor footprint was too small for the flex PCB coverlay web (solder mask). It has been produced as a single opening now, and may be more difficult to solder.

I soldered one of the 0603 LEDs by hand and it's possible, but not so sure about the processor and 0402 resistors. I've ordered some "low temperature" solder paste and a hot air tool (although I didn't get a stencil because I was being cheap, and the plan was to make a solder paste extruder for my pick and place machine project) to try soldering some more of the LEDs and try if it all breaks apart during installation.

animated gif of a round flexible PCB of orange polyamide taped to a blue background. Only the central LED has been soldered, and flashes white as multimeter probes are touched to the contacts
It lights up!

March, 2026

I started on a flexible version of the bottleship-hex-61 prototype board.

As I wanted to fit within JLC's "special offer" size of 100x100mm, I started with the PCB panel arrangement. I determined the maximum dimensions of each board and their placement on the panel using SolveSpace to work out the constraints. This gave me a 42mm circle with a 10×10mm tab on one side to work with, just enough to fit the microcontroller and connector pins. I tweaked the hexagonal arrangement to pull the LED's on the outermost ring onto an actual circle with even spacing. This does result in a slightly less evenly spaced arrangement overall but should be more suitable for mounting in a round bottle or jar where it is mostly viewed from the sides. I used kikit to panelize and prepare the gerber files as before, but this time wrote a custom layout plugin that would put the boards in the specific positions and orientations. I also attempted to make the panel more suitable for laser cutting (using --copperfill for extra stability, --framing 'tightframe; slotwidth: 0.5mm;' for a thinner outline slot, and --cuts 'none' to leave the tabs to be cut with a knife or scissors later).

Maybe I will try soldering the LEDs on one of them by hand. Unfortunately I missed that JLC require 0.5mm gaps between exposed pads in the solder mask layer (coverlay web) for flex PCBs, so the 3x3mm QFN-20 package of the CH32V003 will arrive with one big opening and probably be impossible to solder by hand.