# ESD damage and relative humidity

Discussion in 'Electronic Design' started by garyr, Jul 26, 2013.

1. ### garyrGuest

What is the likelihood of ESD damage occurring if the relative humidity is
100%?

2. ### Syd RumpoGuest

About 4.3%, or 100/(e^pi) as a first good approximation, although
bilateral effects caused by Cauchy scattering have some effect in areas
of significant frombulism.

Cheers

3. ### DaveCGuest

What is the likelihood of ESD damage occurring if the relative humidity is

http://esdsystems.descoindustries.com/whitepapers/wp_humidity.html

Remember that junction failure isn't the sole possible outcome of an ESD
event. Weakening ("degrading" in ESD parlance) of junctions will shorten
operational life, not evident immediately after an event.

3M has a nice handbook:

http://www.digikey.com/Web Export/Supplier Content/3M_19/PDF/3M_StaticCont
rolMeasures.pdf?redirected=1

With polyester carpet, I think even underwater you could get a healthy shock!
(c; <<<- note smiley

Dave

4. ### Guest

Pretty low. Unless there is an electric eel nearby.

Matt Roberds

5. ### John SGuest

So, it was the tepid water they objected to?

Chilly water makes for more turgid nipples.

7. ### Guest

You should be able to model the situation with your circuit connected
by a variable resistance to a charged capacitor. Some of the charge
will bleed to nearby ground planes, while the rest goes to ESD
sensitive parts.

With a constant voltage source (say 10 kV) connected to the capacitor
a few cm from the device, the maximum constant leakage current can be
calculated.

Alternatively, charge up the capacitor and let it discharge through
the resistance and get the RC time constant for different distances.

If a charged finger moves towards the device at constant speed, the
resistance drops rapidly, discharging the human body model capacitor.
How low does the voltage drop just before contact ?

Some interesting data can be found with Google search expression like
"moist air conductivity" (with quotes). It appears that the air
conductivity will increase with at least two orders of magnitude, when
going from dry to moist air.

8. ### John SGuest

They objected to the nipples or the turgidity? We need to get to the
root of the problem. Or something.

9. ### Guest

Soldering, or mechanical assembly? There are places *I* never want to
feel a drop of hot solder and I am sure ladies have similar concerns.

Mechanical assembly might be OK as long as you don't mind occasionally
losing washers and stuff down the tub drain, and having to replace rusty
hand tools.
They wanted naked old people instead?

Matt Roberds

Blame Milla Jovovich. OMG! They're full of milk!

DAMNIT, Janet! *I* wanted to marry her!

We'll never find out now! She'll probably never sport those torpedoes
in a flick again. It is truly a sad day. :-(

(just kidding)

11. ### Jasen BettsGuest

That depends if you go out in the rain or not

Raindrops are often electrostatically charged.