Vented lid for Raspberry Pi 4

Description

A 90x62 mm lid for the usual flat Pi 4 case. Nine 4 mm slots run along the board directly over the SoC; under load that is 8-10 C better than a closed lid, measured with a thermocouple on the chip rather than by hand.

A 4 mm rim runs round the edge and centres the lid in the base without screws. The four 2.8 mm holes take M2.5 standoffs if you want it bolted down.

Print slots up, no supports: 4 mm gaps bridge without sagging. If you use PLA, bear in mind a loaded Pi 4 brings the case to 45 C, and a lid in summer sun can warp.