Depends (Dough TM). If you assemble millions of cards and to sigma 6, then even small percentage of local solder problems causes huge problems. One single pad issue can stop a mass production line for days, Well, it's too long for debating. Inge -------------------------------------------------- From: "Bob Landman" <[log in to unmask]> Sent: den 18 April 2010 09:59 To: <[log in to unmask]> Subject: Re: [TN] PCB Shelf life > We have found ENIG and HASL to have 1 year+ shelf life without any special > care being taken > for boards of various sizes (from 2" x2" up to 4" x 6"). > > Bob Landman > H&L Instruments, LLC > > ----- Original Message ----- > From: Inge > [mailto:[log in to unmask]] > To: [log in to unmask] > Sent: Fri, > 16 Apr 2010 13:33:32 -0400 > Subject: Re: [TN] PCB Shelf life > > >> We have found a factor that is not to be found in any standard or >> paper, >> namely, the size of the components. If you have e.g. a mobile >> telephone >> card, all components are the tiniest that are to be found on the >> market. >> With that follow extremly small solder pads equal to extremly >> small solder >> volumes. Such card are more sensitive to solder tarnish than >> board with >> much bigger components. Therefore, Ericsson have a storage >> maximum of a >> couple of weeks only. I have never seen a investigation of that >> condition. >> Nor any calculations or rules. >> >> Inge >> >> -------------------------------------------------- >> From: "Bill Belanger" <[log in to unmask]> >> Sent: den 16 April 2010 10:14 >> To: <[log in to unmask]> >> Subject: Re: [TN] PCB Shelf life >> >> > Hello Angel, >> > >> > As a former PCB fabricator, I'm not sure that the base material >> has a >> > shelf >> > life. It's usually quite stable, and lasts a very long time in >> the field. >> > >> > Solderability, however, is a different story. Some surface >> finishes can >> > preserve solderability for many years, such as HASL (Hot Air >> Solder >> > Level), >> > which essentially coats any exposed copper with solder. Others, >> such as >> > immersion tin and OSP (Organic Solderability Preservative), >> measure their >> > shelf life in months, weeks or days. >> > >> > Hope this helps, >> > >> > Bill Belanger >> > >> > --------------------------------------------------- >> > 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 >> > ----------------------------------------------------- >> >> >> ______________________________________________________________________ >> This email has been scanned by the MessageLabs Email Security >> System. >> For more information please contact helpdesk at x2960 or >> [log in to unmask] >> ______________________________________________________________________ >> >> --------------------------------------------------- >> 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 >> ----------------------------------------------------- >> >> > > ______________________________________________________________________ > This email has been scanned by the MessageLabs Email Security System. > For more information please contact helpdesk at x2960 or [log in to unmask] > ______________________________________________________________________ > > --------------------------------------------------- > 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 > ----------------------------------------------------- ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- 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 -----------------------------------------------------