Gabi,

A couple of things for you to consider.

You don't want to base your gap size on breakdown in air.  You will need to
account for the dielectric material of the PCB and possibly a conformal
coating or solder mask on top of the etch.

You need to decide whether or not you really want a discharge gap inside
your unit possibly close to critical components.  A breakdown inside your
unit may be more trouble than the problem it solves.

Bob Howland
dBH Consulting

-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Gabi Hoffknecht
Sent: Wednesday, February 20, 2002 11:33 AM
To: [email protected]
Subject: Using PCB traces as transient voltage suppressor



Hi all,

I have seen PCB designs with two triangular shaped copper pads pointed
towards each other at very close proximity, meant as an air gap discharge
path for transients. Does anyone have information about such designs,
whether they work and how well ? At a breakdown voltage for air of 1
Megavolt per meter, they should theoretically work: 10mil distance would
have a breakdown voltage of only 254V. Such a PCB design basically comes for
free, so I was thinking of adding it on top of my already existing series
impedance - TVS network.
Thanks in advance for your comments.

Best regards,
Gabi Hoffknecht

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