Maximum Voltage between PCB layers?

[Magnethicc]

How can I ensure sufficient voltage insulation between layers of PCB?
for example 800V between 2 conductors placed on 2 different layers, how can I figure out what needs to be the prepreg/core thickness to ensure safe operation? (lets assume it is mains connected tracks so overvoltages and transients can occure).

Thank you.

 

[KlausST]

Hi,

I´d surely conduct my PCB supplier.
Different material, different ways to produce (like vakuum laminating), different precision standards, different layer count .... and and and...

Klaus

 

[ahsrabrifat]

Determine the minimum dielectric thickness (prepreg/core) required between two conductors placed on different layers of a PCB to safely withstand 800V (AC or DC), considering safety margins for mains-connected applications. You must follow some safety standards including IEC 60950 / IEC 62368,UL 796 , UL 94,IPC-2221B,IEC 60664-1. These standards define clearance, creepage, and dielectric breakdown requirements. The following links will give you some guidelines.

https://www.advancedpcb.com/getattachment/951519e6-0c82-41f7-ab09-433579bd6d5b/prepreg-thickness-chart.pdf

PCB Conductor Spacing and Voltage Calculator | Sierra Circuits

Try the PCB Conductor Spacing and Voltage Calculator to get your minimum spacing between two conductors right.

www.protoexpress.com

Detailed PCB safe distance - Engineering Technical - PCBway

Safe distance , including clearance ( spatial distance ) , creepage distance ( creepage distance ) and distance through insulation Clearances : two adjacent conductor or a conductor with the shortest...

www.pcbway.com

 

[Magnethicc]

Okay thank you for your answers, I see the figure 0.4mm comes up alot which is interesting.

I'd I find something concrete I will update here.

 

[FvM]

"Safely withstand 800 V" is no full specification. We have working voltage or test voltage, functional, basic or reinforced insulation, different overvoltage categories.

Quoted 0.4 mm minimal insulation thickness can be e.g. found in IEC61010 in paragraph 6.7.2.2.3 Inner insulating layers of printed wiring boards and is valid for reinforced insulation of mains circuits < 300 V phase to neutral and any overvoltage category. It can be used without further considering substrate voltage strength. There are similar default insulation thickness values for higher mains voltages specified.

Alternatively you can refer to specified test voltages for the respective insulation category and manufacturer voltage rating which usually allows considerably thinner insulation layers.

To answer the specific 800 V question, please explain across which isolation barrier the voltage is observed.

Hardest reinforced insulation requirements are e.g. only applied for safety critical isolation between high voltage and exposed low voltage circuit.

 

[marce]

Get the material specs for the board you are having manufactured, then work out the thickness of dielectric required to give you the required insulation for the voltage difference, you have to isolate.
For general designs, just to be safe I keep at least 0.4mm between higher voltage traces. I.e. don't put them on the next layer down on a 4-10 layer design. If possible go for top and bottom layers and you have plenty of insulation.
FR4 is a good insulator...
FR4, a common PCB substrate material, has a typical dielectric strength (breakdown voltage resistance) ranging from 800V/mil to 1500V/mil, or 45-70 kV/mm. This means it can withstand a voltage of 800 to 1500 volts for each mil (0.001 inch/0.0254mm) of thickness. The actual breakdown voltage can vary based on factors like manufacturer, resin content, glass weave, and the presence of voids.