I'm not aware of any standards for long term storage, but we've stored some boards for many years, so here's some opinion. Tin/lead finish doesn't oxidize very readily, so I'm not sure about the value of storing in nitrogen, unless you're trying to keep the boards dry. But if you want to keep them dry, you can do as well with dry-pack, i.e. a heat-sealed moisture barrier bag with desiccant and humidity indicator card. According to J-STD-033, this kind of dry-pack system is good for at least 12 months at <40C/90%RH. In practice, it's good for quite a bit longer than that, but if you want some insurance, double-bag them (seal the first bag inside a second). The biggest problem with long-term storage will be intermetallic growth, which depends on time and temperature. This often shows up first with solderability problems at the knee of the plated-through hole ("weak knee"). But if you have good tin/lead thickness, it shouldn't be an issue. If you want to slow down this reaction, about the only thing you can try is to keep the boards cool, but this won't help much, and introduces other complications. -Joe -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of [log in to unmask] Sent: Thursday, July 15, 2010 5:28 AM To: [log in to unmask] Subject: [TN] PCB storage Hello Technetters, we have to store High reliability SnPb assemblies for some years. They will be stored under N2 cabinets and temperature 22°C±2°C. Are there any standards about the storage times or technical articles on the subject ? Thanks. CANTAGALLO Luigi Technology Engineer [log in to unmask] ______________________________________________________________________ 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 -----------------------------------------------------