Anil
Yes! I agree that this does not help. However, a French client of mine has traced
wind-borne sea salt inland under some weather conditions, so this factor may be more
serious than is commonly thought.
The strategic computer room of a UK Royal Navy ship, placed right in the interior of
the structure, is equipped with the most sophisticated air conditioning/filtering. One
such ship, in dock for refitting, had a fitter wedge the door open for a job he was
doing where space was limited, for a couple of days during what was reported as winds
of 3 -4 Beaufort. I was informed that malfunctioning of some equipment occurred and,
as a safety measure, the totality of the equipment was replaced. This was reported to
me by an ex-Ministry of Defence employee.
Even worse is salt scattered on roads for ice prevention. The wheels of passing
vehicles throw up a mist of concentrated brine which spreads everywhere.
I reported these phenomena in my book published in 1986.
Brian
Anil Kher wrote:
> Upto 1 km inland of coastal areas and during monsoon there is 50 ppm of salt
> in the aerosol owing to heavy surf / winds. This tends to enter the
> electronic instrument chasis and can condense at dew point on the PWB.
> This environment would be HARSH.
> Anil Kher
> ----- Original Message -----
> From: Brian Ellis <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Wednesday, December 29, 1999 12:47 PM
> Subject: Re: [TN] Harsh Environments?
>
> > David
> >
> > Sorry, I'm not with you on this one. 20 - 25°C/40-80% RH is a perfectly
> normal
> > office-type environment. In my view, a mildly harsh environment starts at
> about 35°C
> > XOR a RH > 80% or a harsh one at 30°C AND > 75% RH. Where I live, we have
> summer temps
> > up to 47°C with low RH and our car electronics (even radio and
> window-winders) perform
> > normally after the car has been sitting in the sun and you cannot touch
> anything
> > inside, it is so hot. Last night, in midwinter, the temp dropped to 13°C
> and there was
> > an equivalent dew point, indicating 100% RH, with c. 1 mm of precipitation
> in the form
> > of condensing dew. Again, external electronics worked fine, including
> cheap movement
> > detectors. I cannot be persuaded that either of these conditions are
> really "harsh", so
> > much as normal.
> >
> > The ionic contamination is not part of the environment and a cut and dried
> figire of
> > 1,5 µg/cm2 eq. NaCl is meaningless without knowing the applications, type
> of circuitry
> > etc. In some cases, with low voltage gradients, this level would be
> perfectly safe even
> > at 80°C/90% RH. On some HDIS circuits with high voltage gradients, even
> 1/10 this level
> > may be dangerous, provoking something akin to Doug Paul's arc welder.
> >
> > I honestly do not believe one can be categorical about this kind of thing.
> Perhaps you
> > would like to expound further as to your reasoning????
> >
> > Have a good pre-millennial year
> >
> > Brian
> >
> > David Douthit wrote:
> >
> > > Technetters,
> > >
> > > I would like some expert opinions on what constitutes a "harsh
> > > environment".
> > > In order to stimulate some debate the following is one proposed
> > > definition.
> > >
> > > "Due to the highly competitive nature of the electronics industry and
> > > costs of coating the issue of whether coating is required or not can
> > > become a hotly debated topic. The primary issue is "What is a harsh
> > > environment?".
> > >
> > > The following general rules can be considered as the boundary line
> > > condition for a "harsh environment". There are three minimum conditions
> > > which must exist in the localized area of the circuitry at the same time
> > > with or without power applied:
> > > 1. A relative humidity of 60% or higher.
> > > 2. Temperatures above 0 degrees C.
> > > 3. The deposition of ionic contaminates on the circuitry surface which
> > > will exceed 1.5ug
> > > of NaCl or its' equivalent per square cm during the expected
> > > lifetime of the product.
> > >
> > > Consideration of these conditions must also include shipping, storage,
> > > and handling of the product. These conditions are a reference point and
> > > exceptions are possible. Researching these environments are required to
> > > determine if these conditions exist."
> > >
> > > Thank you for your time.
> > >
> > > D. A. Douthit
> > >
> > > ##############################################################
> > > TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
> > > ##############################################################
> > > To subscribe/unsubscribe, send a message to [log in to unmask] with
> following text in
> > > the body:
> > > To subscribe: SUBSCRIBE TECHNET <your full name>
> > > To unsubscribe: SIGNOFF TECHNET
> > > ##############################################################
> > > Please visit IPC web site (http://www.ipc.org/html/forum.htm) for
> additional
> > > information.
> > > If you need assistance - contact Gayatri Sardeshpande at [log in to unmask]
> or
> > > 847-509-9700 ext.5365
> > > ##############################################################
> >
> > ##############################################################
> > TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
> > ##############################################################
> > To subscribe/unsubscribe, send a message to [log in to unmask] with
> following text in
> > the body:
> > To subscribe: SUBSCRIBE TECHNET <your full name>
> > To unsubscribe: SIGNOFF TECHNET
> > ##############################################################
> > Please visit IPC web site (http://www.ipc.org/html/forum.htm) for
> additional
> > information.
> > If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or
> > 847-509-9700 ext.5365
> > ##############################################################
> >
>
> ##############################################################
> TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
> ##############################################################
> To subscribe/unsubscribe, send a message to [log in to unmask] with following text in
> the body:
> To subscribe: SUBSCRIBE TECHNET <your full name>
> To unsubscribe: SIGNOFF TECHNET
> ##############################################################
> Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
> information.
> If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or
> 847-509-9700 ext.5365
> ##############################################################
##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in
the body:
To subscribe: SUBSCRIBE TECHNET <your full name>
To unsubscribe: SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or
847-509-9700 ext.5365
##############################################################
|
