Was the test performed on the flex itself and not the whole assembly? If the answer is ' yes', I do understand better, because then the test was a test on the PI's resistance to humidity. With other words, a water vapour penetration test. Inge ----- Original Message ----- From: "Eric CHRISTISON" <[log in to unmask]> To: <[log in to unmask]> Sent: Wednesday, June 25, 2008 9:50 AM Subject: Re: [TN] Bias voltage test in damp heat > Alternatively you could suggest to the customer that they save time on > qualification by ditching the 1000 hours 85/85 and simply submerge the > equipment in a bucket of warm water for a day. The water uptake will be > much the same. > > Good luck. > > > > Douglas O. Pauls wrote: >> Steve, >> I agree that this is madness, unless the telecom supplier has an end use >> environment of 85/85 where power-on in humid conditions is a reality. >> Assuming that the equipment is not functioning in a steam environment, >> here is the "science" that you are looking for. >> >> Designers, when they have knowledge of the material characteristics, will >> design spacings dependent on the dielectric strength or dielectric >> withstanding voltage of the laminate. The values in the data sheets for >> the laminates specify these parameters, but only for lab ambient >> conditions, not after 85/85 conditioning. When you expose a hydrophilic >> material to a long exposure in hot/humid conditions, then you don't have >> that same dielectric strength (dramatically reduced) and you have >> violated the design assumptions. Polyimide is such a hydrophilic >> material. I believe Brian Ellis referred to it as blotter paper, in >> which I would concur. If you allow the circuit to dry out, then you >> return to the expected dielectric strength. You may already be at an >> unrealistic threshold with 2500 volts/mm gradient, as Brian also pointed >> out. >> >> Unless the designer had a firm value for dielectric strength of the >> substrate after 85/85 conditioning, which would change as the substrate >> rapidly dried out, then the design would not and could not work. >> >> Doug Pauls >> >> >> >> >> Steve Kelly <[log in to unmask]> Sent by: TechNet <[log in to unmask]> >> 06/25/2008 10:09 AM >> Please respond to >> TechNet E-Mail Forum <[log in to unmask]>; Please respond to >> Steve Kelly <[log in to unmask]> >> >> >> To >> [log in to unmask] >> cc >> >> Subject >> [TN] Bias voltage test in damp heat >> >> >> >> >> >> >> Good Day To All, >> >> Back in April I posted some queries on the tech-net about high voltage >> testing after 85C/85RH testing and was basically told this test was >> impossible and I agree with that assessment. But some things have a life >> of >> their own. >> >> To re-iterate: We are building a 4 layer flex circuit. All layers are 18 >> micron copper and all lines and spaces assuming perfect etch are 100 >> micron >> lines and 100 micron spaces. My customer for some reason signed up to >> pass a >> 250 volt test after 1000 hours of 85C/85RH damp heat test. My premise is >> being in this case a polyimide build if they dried the circuit after this >> test it should pass. They do not want to dry it and still have it pass. >> The previous threads in summary said this test was "madness" - I agree >> but >> what is the scientific explanation of why this is madness. >> Please note this requirement is being driven by very large telecom >> companies >> and the worlds largest provider of internet gear. >> Thanks again for the help. >> >> Regards Steve Kelly >> >> >> Steve Kelly >> >> (416) 750-8433 (work) >> >> (416) 750-0016 (fax) >> >> (416) 577-8433 (cell) >> >> >> >> --------------------------------------------------- >> Technet Mail List provided as a service by IPC using LISTSERV 15.0 >> 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 15.0 >> 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 >> ----------------------------------------------------- >> >> > > -- > Eric Christison Msc > Mechanical Engineer > Consumer & Micro group > Imaging Division > > STMicroelectronics (R&D) Ltd > 33 Pinkhill > Edinburgh EH12 7BF > United Kingdom > > Tel: +44 (0)131 336 6165 > Fax: + 44 (0)131 336 6001 > > --------------------------------------------------- > Technet Mail List provided as a service by IPC using LISTSERV 15.0 > 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 15.0 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 -----------------------------------------------------