Hi Paul, This is one of those "It Depends" questions. Most of the studies I have read with respect to storage of tin-lead HASL boards suggests a shelf life of up to twelve months. I have not seen any studies for boards with that surface finish being stored for that extended period of time (2 years). In my opinion, the ideal situation would be to purchase the boards as you need them and eliminate the issues surrounding extended storage. But since you already have the boards that is not an option. My 2 cents are to make sure that if you plan on storing them, that you package for the long term (2 years) and not for the short term (6mos). I would suggest vacuum packaging them in a clean, moisture and debris resistant container (e.g. Kapak heat-sealable bag). Depending on how many boards you have to store and their dimensions, it may be advisable to store them in a dessicated environment after vacuum sealing them. Controlling the humidity is going to be key to reducing the oxidation rate. Unless you use a nitrogen blanket to store the boards, you will not eliminate oxidation, but by controlling the humidity, you should be able to slow the process a bit. It is hard to say what will happen after long term storage, but I would suggest checking a few boards (provided you have extra) for solderability. If the boards solder as you expect, then you may be safe to continue to assembly. If you have problems, you may want to consider a mild saponified wash to remove any oxidation or debris that has accumulated from storage and repeat the solderability. Best of luck! Joe Russeau Process Analyst Precision Analytical Laboratory, Inc. 4106 Cartwright Dr. Ste. A Kokomo, IN 46902 P: 765-455-1993 F: 765-455-1996 E: [log in to unmask] ----- Original Message ----- From: "Black, Paul" <[log in to unmask]> To: <[log in to unmask]> Sent: Tuesday, August 09, 2005 2:31 PM Subject: [TN] PCB Storage > Hi All, > > I have some bare PC boards that may be built up in the future, but not in the near future. I would like to put them into storage until needed (anywhere from 6 months to 2 years). The boards are .062" FR-4 HASL boards. What would you recommend for protection, assuming that the storage conditions are typical of an office environment? Would I have to do anything special to them when they are removed from storage? Any suggestions would be greatly appreciated. > > Thank you, > Paul Black > Manufacturing Engineer > Kronos > E-mail: [log in to unmask] > > --------------------------------------------------- > 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 -----------------------------------------------------