Clear polyolefin heatsink from 3M worked OK and it was possible to seal the ends by melting. I could not find one with glue.
However, I'm trying to go forward with a custom enclosure made from polycarbonate. I have designed it to be openable and sealed with an O-ring. The O-ring is set up as piston cylinder style.
The PCB became even thinner (3.1 mm) allowing the enclosure to be only 4.7 mm. Now my problem is to find suitable screws for such a small and thin enclosure. The screws need to be recessed into the enclosure. The total lenght of the screw (including the head) must be less than 4.5 mm, preferably 4 mm to allow some tolerance. The thickness of the enclosure halfs at the screws is 2.2 mm, since there will be 0.3 mm thick fabric in between. Due to O-ring configuration no compression from screws is needed, it's enough to just keep the halfs together.
The first installation and possible battery change after a few years is done by the user. The screws must work at least 3 times.
What kind of screws would fit this application? Thread forming screws or machine screws? What kind of nut arrangement for the latter?
The suitable size would be M2 (or #2). Thread forming at only 4 mm length are very hard to find and surpricingly expencive. Will they hold with such a short thread? Only 1.5-2 mm.
Also M2 thread incerts for only 2.2 mm thickness are hard to find. I found one, but it seems not designed for recessed installation. Square or hexagonal nuts can be found at 1.2 mm thickness. Would making a recession for it work?
The screws need to tolarate weather. Maybe A2 or brass is OK?
At least the first enclosures will be CNC machined, since the mold cost approximations I have got have been 5 000-10 000 €. Is that expected?