Neil, Depend upon what kind of oxide on the surface of the HASL board, for Pb/Sn finishing. If you form the lead rich oxide, it actually grow thicker and causes solderability problem after storage. I agree with you that normally the tin rich oxide at the HASL surface is very stable (shinning oxide) and normally do not grow much after its formation. However, the lead-rich oxide (dull looking) normally is not that stable... grow relatively fast after the initiation(I am sure someone in their early life did PhD on it... Not me...). my 1.64 cents... jk -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Atkinson, Neil Sent: Wednesday, August 10, 2005 12:37 PM To: [log in to unmask] Subject: Re: [TN] PCB Storage Any oxidation will take place very quickly and has little effect on the long term solderability which for HASL boards is dependant on SnPb thickness and storage temperature. Intermettalic growth rate increases exponentially with temperature - I love the freezer idea! Check out this link at the National Physics Laboratory here in the UK. http://www.npl.co.uk/ei/presentations/storage.pdf They found some interesting results where plastic bags appeared to have a detrimental effect on the solderability of various PCB finishes. Neil ________________________________________________________________________ This e-mail has been scanned for all viruses by Star. The service is powered by MessageLabs. For more information on a proactive anti-virus service working around the clock, around the globe, visit: http://www.star.net.uk --------------------------------------------------- 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 -----------------------------------------------------