[Moved] what does incisions in a board mean?

[at89atbits]

I came across a statement "analog front ends can be protected against leakage currents by incisions in board layout".
What does incisions in the board layout mean?
How is it obtained?

 

[zsolt1]

Re: what does incisions in a board mean?

the statement is not common .... probably : if you cut the circuit from the board it's 100% shore that the analog front and is protected against leakage currents :laugh: (of course because nothing will pass to the board ). Now seriously : generally you can protect analog front ends by adding series current limiting rezistors & zenner diodes to cut off spikes.

 

[esp1]

Re: what does incisions in a board mean?

hi,
Its sometimes done on PCB's that carry high voltages.

The actual PCB material is completely cut away between the copper tracks, leaving an open 'slot' between the tracks.

E

 

[zsolt1]

Re: what does incisions in a board mean?

esp1 pointed right if the context is about high voltages. When working with high voltages (>1kV) spark gap's (eclators) can be used as cheep protection devices. At an over voltage pulse coming to the spark gap , the electric field between the tracks exceeds a critical level and a breakthrough (spark) occurs in the dielectric (the air) so it can't propagate further on the circuit. The critical level is distance dependent, so the protection level can be adjusted. If you need more explicit info about this just ask

 

[marce]

ESP1 is talking about slots to minimise the creepage distance between conductors, look up clearance and creepage on the web...ISO-60950

Could the original poster links us to the document the statement comes from.

 

[D.A.(Tony)Stewart]

Surface contamination is worse than air for leakage as well as charge buildup leading to HV breakdown. In these situations where this is important air slots are milled in the design.

this interior milling operation is an inclusion. There may be other reasons for mounting hardware or cutouts.

Each inclusion is another step in the process , but usually a minor step with automated drill, mill toolsets if within limits.

 

[marce]

Hence creepage distance is approx. 2X clearance distance

http://www.creepage.com/