I want to design a four layer PCB, where on the top and second layer are voltage up to 600V present. While I find many information about trace spacing, I don't find anything about isolation between the different layers. Is it possible and safe to have a voltage (difference) of 600V between two (or more) layers?
I'm planing to use a normal FR4 PCB and I know the breakdown voltage of 300V/mil. But is the breakdown voltage also safe?
Electronic – High Voltage Multilayer PCB
multi-layerpcb
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Best Answer
Yes you should be fine as long as you take care with the design
The IPC-2221 provides typical electrical properties for common materials (FR4, Polyimide etc... ) & as you stated, the electrical strength is around 39kV/mm.
A copper clad laminate would therefore, in theory, be perfectly capable of withstanding 600V.
That said ... There are a few consideration and not just in the x-y plane with regards to trace separation (again IPC-2221)
Pad & track corner design. Round them off to mitigate buildup of charge & maximise the corona inception voltage. This is a must for medium voltages & not so much with the low voltages of 600V, unless altitude is a real consideration.
FR4 absorbs moisture quite readily & this reduces the electric strength capability.
Prepreg voiding (and also laminations) While in theory the electric strength is 39kV/mm, in practice manufacturing can result in localised areas that do not meet this.
My personal recommendation would be to separate the high voltage via the prepreg instead of the laminate. Double-prepreg the stackup as well to mitigate instance of voiding (what is the probability that two voidings occurrences align? ).