I cannot find clear information on running mains and low voltage on adjacent layers on FR4 PCBs. I understand how much creepage distance to allow, but for example, can I run - 50Vdc, 240Vac, 0Vac, ground, on a 4 layer 1.6mm FR4 PCB. Would it be more appropriate to use a 6layer pcb, leaving blank layers between 50V/240Vac/0Vac?
Could someone point me to a standard on this? I have had not much luck with Kervill's Low Voltage Directive.
Answer
This is information you get from the datasheet of the prepreg/laminate you use. Example here from Isola: http://www.isola-group.com/wp-content/uploads/2012/09/IS420-Lead%C2%ADfree-Laminate-and-Prepreg-Data-Sheet-Isola.pdf
This specific material datasheet show something like 30 kV isolation per mm material layer to layer.
If you rely on this, make sure the material is fully specified in the PCB fab drawing.
Also note you can pretty much count on the laminate thickness, but the Cu traces will sink into the prepreg effectively reducing the resulting layer to layer distance.
No comments:
Post a Comment