Do COB LEDs usually need electrically insulating from the heatsink?
Do COB LEDs usually need electrically insulating from the heatsink?

The LED chips inside the module are already isolated from the heatsink on the back. They must be because these modules contain many LEDs in series and that is why they need around 20 - 30 V to work. Each LED needs around 3 V so there must be many in series.

This can only work if all LEDs are isolated from the heatsink. So you can safely assume that the heatsink is already isolated from the LEDs . I would not make the voltage difference too large though but up to 50 V should generally be OK.