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November 2005

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TechNet E-Mail Forum <[log in to unmask]>, "Whittaker, Dewey (AZ75)" <[log in to unmask]>
Date:
Tue, 29 Nov 2005 14:49:20 -0700
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TechNet E-Mail Forum <[log in to unmask]>, Cheryl Johnson <[log in to unmask]>
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Cheryl Johnson <[log in to unmask]>
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MY daughter dropped phone in toilet first week she had it.  Took it back, we
didn't have extended warranty.... Wasn't going to buy her ANOTHER one.
Friend took it apart, dried it out... one week later, it just started
working again.
Months later, she lost it - we cancelled her number, phone bill has never
been so low...

Sincerely,
-----------------------------------
Cheryl Johnson, C.I.D.+
Manager
ExcelStor US Office, Engineering Services
Email: [log in to unmask]
Tel: (303) 684-7291
Fax: (303) 684-7268
Mobile: (303) 809-5815
-----------------------------------


-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Whittaker, Dewey
(AZ75)
Sent: Tuesday, November 29, 2005 10:55 AM
To: [log in to unmask]
Subject: Re: [TN] Humidity and enclosed RF board


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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