We are working on a product that contains an LED module consists of 66 LEDs (33s x 2p - 100VDC load voltage).
We'll use aluminum PCB due to the thermal requirements but the customer requirement claims that the insulation voltage for the aluminum PCB should be at least 1kV.
The PCB company manufactured the PCBs for us according to the requirement above then we tested it in our lab. Here's the test procedure:
- Short the supply terminals of the LED module.
- Apply increasing AC voltage gradually between the back side (i.e. aluminum) and the front side (the shorted terminals) until the generator stops (The generator beeps then stops automatically under a faulty condition -e.g. short- so we can determine the insulation voltage).
The results are quite interesting:
- The insulation voltage is lower than 100Vac for an unused, empty PCB.
- The insulation voltage is around 1.2kV for a final LED module (i.e. LEDs placed on the same PCB).
The image below shows an empty PCB (top) and final LED module (bottom):
Is this normal? Where can this difference come from?