The Pi4 does not need a fan. There is a grand total of 10 watts of heat to dissipate, 15 watts max supply but that includes power sent to peripherals and wifi.

The Pi4 does not need a fan. There is a grand total of 10 watts of heat to dissipate, 15 watts max supply but that includes power sent to peripherals and wifi. A matchbox sized heatspreader which just touches each of the warm components will work assuming a bit of ventilation is arranged to let 40-50C air float away. The heatspreader shouldn't even benefit significantly from being a top conductive alloy - a bit of tin lid will do the job. Experiences with shifting 200 watts for cpu cooling has people thinking dedicated alloy sinks and fins and fans are appropriate, but this is just 10 watts - it's child's play ;/