Intermetallic growth rate over time is constant with temperature. Once the intermetallic reaches the surface of either the via or the pad lack of wetting will be come apparent particularly on the areas of the pad that were entering the air knife first since these can show very thin tin lead thickness'. To really answer this question you need to know how thick the tin lead is and then you can give an indication of storage life at a certain temperature. The thinner the HASL the shorter the storage life at a given temperature. The lower the temperature the longer the storage life for a given thickness of HASL. "Pack 'em in dry nitrogen gas and throw them in the freezer" would maximise the solderability in any event. John ------------------------------------ Avanex John Burke Senior Manager RoHS Compliance [log in to unmask] 40919 Encyclopedia Circle Fremont CA 94538 tel: 510 897 4250 fax: 510 979 0189 mobile: 510 676 6312 ------------------------------------ -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Dehoyos, Ramon Sent: Tuesday, August 09, 2005 1:13 PM To: [log in to unmask] Subject: Re: [TN] PCB Storage I have encounter resistance from a mentality type of folks that strongly argue that HASL boards need to be etched and replated after 12 months. These people recommend TIN/LEAD uplating instead of HASL if the boards are not going to be used within a year. Their argument is that the intermetalics in the barrels would render the boards unsolderable. Any thoughts on this mater? Ramon -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Franklin Asbell Sent: Tuesday, August 09, 2005 4:01 PM To: [log in to unmask] Subject: Re: [TN] PCB Storage While I certainly do not recommend this practice, I had some boards in my desk for 5 years, under some papers, beneath a box...I had 'forgotten' they were there, just for kicks I soldered them without bake and they looked good. For storage in an office (or controlled)environment I would suggest vacuum seal with dessicant for the environment you suggest. Time in itself for that period should not be an issue, just keep them sealed and they may last up to 7 years or more. Franklin -----Original Message----- From: Black, Paul [mailto:[log in to unmask]] Sent: Tuesday, August 09, 2005 2:32 PM To: [log in to unmask] 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 ----------------------------------------------------- --------------------------------------------------- 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 -----------------------------------------------------