[Carl] wanted to put his force sensors on a transparent PCB and had to ask his board vendor for a special sample. Flexible PCBs are available on transparent substrates made of PET, but they are not as common as polyimide boards. As [Carl] found out, these boards are a bit thicker, a bit less flexible, and don’t hold up to very high heat as well as the standard boards. Undeterred, he designed a 3D Christmas tree using the clear boards. The result that you can see in the video below looks pretty good and would have been hard to duplicate with conventional means.
When you build the board it is as a flat spiral, but lifting it in the center allows it to expand into a conical tree shape. The circuit itself is just an LED blinker, but the flexible board is the interesting part.
Don’t let the heat put you off, as though the boards deformed at temperatures around 215C and require careful soldering, your projects will probably not run at that temperature.
There was a time when any sort of flexible PCB was a big project. Now it is easily done and not particularly expensive. [Carl] mentions he violates some best practices for the sake of speed and aesthetics, but the result works fine and it looks pretty cool.