Was she just trying to surf the web with her phone?
Dewey
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of John Burke
Sent: Tuesday, November 29, 2005 10:38 AM
To: [log in to unmask]
Subject: Re: [TN] Humidity and enclosed RF board
You mean apart from the one where my daughter ran into the ocean with a
mobile phone in her pocket??........................8-)
John
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Eric CHRISTISON
Sent: Tuesday, November 29, 2005 9:34 AM
To: [log in to unmask]
Subject: Re: [TN] Humidity and enclosed RF board
Agree with Richard about the environment. Letting the enclosure breathe
is also a good plan; how many mobile phones fail due to humidity related
failures?
You might also consider adding a breathing desiccator to the enclosure
although they tend to be expensive and need replaced every six moths or
so.
Regards,
Eric Christison
Mechanical Engineer
Home, Personal, Communication Sector - Imaging Division
STMicroelectronics
33 Pinkhill
Edinburgh
EH12 7BF
Tel: +44 (0)131 336 6165
Fax: +44 (0)131 336 6001
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard
> Sent: Tuesday, November 29, 2005 5:25 PM
> To: [log in to unmask]
> Subject: Re: [TN] Humidity and enclosed RF board
>
>
> It also depends on the environment where the box will live.
> If it is near the sea, there is a much higher probability of failure
> if any moisture does enter from outside.
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas O. Pauls
> Sent: Tuesday, November 29, 2005 11:01 AM
> To: [log in to unmask]
> Subject: Re: [TN] Humidity and enclosed RF board
>
> Well, it depends.
>
> You say that the casing seals the electronics from the external
> atmosphere. How well? Is it a hermetic seal? Are you using an
> elastomeric gasket? Do you package with an inert cover gas? What is
> the design life of the product and what are the consequences of
> failure?
>
> In my experience, even those enclosures assumed to be "hermetic" are
> not, and that usually means moisture will eventually get in and will
> have a hard time getting back out.
> So it all depends on how well insulated your case keeps the
> electronics throughout the design life. Elastomeric gaskets willl wear
> out. Field repair is often less than optimal.
>
> If moisture gets inside the case, it will condense on your boards when
> you go through dew point. Can it grow dendrites?
> Yes. What is the risk? It Depends. Dendrites have been observed to
> grow in as little as 3.5 volts DC. There is no "safe" level of
> humidity because the degree of risk is dependent on both humidity and
> the amount of ionic soil. The dirtier it is, the less humidity it
> takes. Some papers have suggested 70% RH as a threshold, but this is
> usually SIR type of testing, not field trials. In addition, if your
> product is functioning in some of the more polluted areas of the
> world, and the enclosure is not hermetic, then the pollutant gasses
> also get into the enclosure and do nasty things.
>
> Doug Pauls
>
>
>
>
> "Tempea, Ioan"
> <itempea@POSITRON
> .QC.CA>
> To
> Sent by: TechNet [log in to unmask]
> <[log in to unmask]>
> cc
>
>
> Subject
> 11/29/2005 10:43 [TN] Humidity and enclosed RF
> board
> AM
>
>
> Please respond to
> TechNet E-Mail
> Forum
> <[log in to unmask]>
> ; Please respond
> to
> "Tempea, Ioan"
> <itempea@POSITRON
> .QC.CA>
>
>
>
>
>
>
> Hi Technos,
>
> application: one RF board and one antenna, no conformal coating, both
> sealed inside of a casing; outdoor unit, will see temp and humidity
> variations.
>
> question: assuming that the boards are well insulated from the
> exterior, should I worry about long term rel of the boards? Otherwise
> said, due to temp variations, can the residual humidity inside the
> casing condensate on the boards and cause damage? Or can it make grow
> dendrites?
>
> And a general question: For dendrites we need a potential difference,
> humidity and dirt; is there any threshold for the humidity level,
> below which dendrites will not grow?
>
> Thank you,
> Ioan
>
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