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 > > --------------------------------------------------- > Technet Mail List provided as a service by IPC using LISTSERV > 1.8e To unsubscribe, send a message to [log in to unmask] with > following text in the BODY (NOT the subject field): SIGNOFF > Technet To temporarily halt or > (re-start) delivery of Technet send e-mail to > [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE > mailing per day of all the posts: send e-mail to > [log in to unmask]: SET Technet Digest > Search the archives of previous posts at: > http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------