Kimmey, Frank wrote:
>
> Hiya TechNet,
>
> I am trying to find out more info on printed sparkgaps. We are presently
> using 3 different configurations (depending on which one the EE likes
> the looks of). Are there any good guidelines for sparkgap creation
> (other than 7kv/cm) for protection against ESD, Lightning, etc.
> I would appreciate if some of you would share (if allowed) your sparkgap
> footprints (with any test results). If you send me info offline I will
> compile and post the results (followed by offline sends of my final
> report to any interested parties).
> Thanks for all the help!
> FNK
>
> Frank N Kimmey
> EM Designer
> C&K Systems, Inc
> [log in to unmask]
> (916) 353-5366
>
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Hi Frank,

I was wondering if you received any information in response to your
TechNet request for the
design of  "sparkgaps" for EOS (electrical overstress).

If not, the following are some brief considerations:

Do you really want to do it using printed board technology?  Concern:
Depending on the
discharge energy, the plasma formed between the spark gap electrodes
will form a plasma
composed of the electrode metal(s) .  When the vaporized metals will
condense on the insulative
material(s) between the electrodes, in other technologies this is called
plasma plating and PVD
(physical vapor deposition).  The condensed metals will change the
sparkgap's breakdown
characteristics and in EE's lingo cause "jitter".  Depending on the
normal (source) operating
current capability of the conductive patterns, it may be some what
current limited and will
eventually "short" out the conductors, until the next high energy pulse
"blows out" the
conductive/resistive  bridge between the electrodes.  If it's a higher
source of current, the I^2 x R
loss will heat up the conductive bridge and burn it out, or the
conductive bridge will test the short
circuit current capability of the power source, or it may blow the
protection fuse.

I assume you've investigated single or multi-point sparkgaps of various
types; such as pointed,
curved and planar, like the following illustration.

General Types of Single Electrode Configurations:

Point-point ---> <---, Point-Curved ---> (---, Point-Planar ---> |---,
 Curved-Curved ---) (---, and Planar-Planar ---| |---, or other
combinations thereof.

Or the Multi-Electrode Configurations:

Point-Point, Point-Curved, Point-Planar, P, and other variations
thereof.

| |---> <---| |,  | |---> /---| |,  | |---> |---| |
| |         | |,  | |     |---| |,  | |         | |
| |---> <---| |,  | |---> |---| |,  | |---> |---| |
| |         | |,  | |     |---| |,  | |         | |
| |---> <---| |,  | |---> \---| |,  | |---> |---| |

I don't know of any reference data for printed board "sparkgaps" you
might try a literature search
based on sparkgap detonators (if you use the internet, you might be
visited 'in the US' by the FBI
or the AFT organizations).

As you may be aware, the electrical characteristics of the conductive
patterns associated
components may have un-planned electrical effects, such as if the
conductive patterns
(electrically) look-like a lumped-constant transmission line, you may
have a "switched oscillator"
 which will have some serious electrical ringing in the conductive
patterns.  The spark gap may
give you a false sense of security in that it may  not have sufficient
response time (turn-on) to
adequately protect the electrical/electronic circuitry.  ESD (and
lightning) have very short leading
edge rise times (typically < 10 ns).  The ionization time of gasses
(air) is much longer.  Perhaps
you should consider other forms of EOS protection, such as silicone
carbide devices (Transorbers
-- spelling?) which have very fast turn-on times (sub ns and ps).  You
should consider "electrical
field" mapping to ensure the electrical stress concentrations are where
you want them, and lastly,
don't forget that sharply pointed electrodes will more easily
"vaporize" and somewhat change
the sparkgap length with each EOS.

Hope this helps,

Ralph

--
Ralph Hersey

Ralph Hersey & Associates
3885 Mills Way
Livermore, CA 94550-3319
PHN: 510.454.9805
FAX: 510.454.9805
e-mail: [log in to unmask]

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