You could also possibly seal them up with the various methods suggested, and then subject the package to steam-aging. This would simulate long term storage under the worst of conditions. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of bob wettermann Sent: Monday, December 14, 2009 12:14 PM To: [log in to unmask] Subject: Re: [TN] Storing of Copper Sheets Dear Technettters: Thanks for your previous grim assessment of the possibility of extending the shelf life of the tin-coated copper sheets. Since then we have discovered that there may be several commercial products-namely corrosion inhibiting bags and papers, that could help in this particular circumstance. Their chemistry allegedly "coats" and "protects" the surface of the metals to inhibit rust and oxidation. The recommendation from several corrosion barrier bag companies is to place several of the approx 1mil tin-coated (at some point it may be soldered to) sheets into a specially-formulated PE bag. This bag through volatilization and contact will protect the sheets against rust, oxidation. Allegedly it inhibits corrosion as well as oil, water and moisture. The manufacturers are telling us that one can expect efficacy of 18-24 months after heat sealing each bag which could contain no more than 50mm thick in materials. Some manufacturers suggested interleaving similar "saver papers" every 3-5 sheets. They will be stored in a temperature-controlled approximately 68-72F low humidity level environment. Does anyone have experience with some of these products? Do we believe what we are being told? Regards Bob Wettermann PH 847-767-5745 --- On Thu, 12/10/09, Douglas Pauls <[log in to unmask]> wrote: From: Douglas Pauls <[log in to unmask]> Subject: Re: [TN] Storing of Copper Sheets To: [log in to unmask] Date: Thursday, December 10, 2009, 10:55 AM Nope, been a resident of Deweyville for many years now. Been thinkin' of runnin' fer mayor next year....... Doug Pauls Steven Creswick <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 12/10/2009 10:06 AM Please respond to TechNet E-Mail Forum <[log in to unmask]>; Please respond to Steven Creswick <[log in to unmask]> To [log in to unmask] cc Subject Re: [TN] Storing of Copper Sheets Doug, You are treading into Dewey's territory now... :-) Steve -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls Sent: Thursday, December 10, 2009 9:16 AM To: [log in to unmask] Subject: Re: [TN] Storing of Copper Sheets Though one would have to ponder if this would lead to cold solder joints...... Doug Pauls "David D. Hillman" <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 12/10/2009 07:33 AM Please respond to TechNet E-Mail Forum <[log in to unmask]>; Please respond to [log in to unmask] To [log in to unmask] cc Subject Re: [TN] Storing of Copper Sheets Hi Steve! Not off the top of my heat. I am pretty sure I have the activation energy in my database somewhere but it would take some time to dig it out. As Syed pointed out, there is going to be a diffusion limit or at least a practical limit point where which would make freezing copper sheets an action worth taking. Dave Steven Creswick <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 12/09/2009 07:24 PM Please respond to TechNet E-Mail Forum <[log in to unmask]>; Please respond to Steven Creswick <[log in to unmask]> To [log in to unmask] cc Subject Re: [TN] Storing of Copper Sheets Dave, Any idea what the average net activation energy might be?? Steve C -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Syed Ahmad Sent: Wednesday, December 09, 2009 6:53 AM To: [log in to unmask] Subject: Re: [TN] Storing of Copper Sheets Depends upon activation energy?! -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman Sent: Tuesday, December 08, 2009 4:59 PM To: [log in to unmask] Subject: Re: [TN] Storing of Copper Sheets Yes, freezing would extent the time some length but I don't know specifically how long without running the numbers thru the diffusion equation. Dave "John Burke" <[log in to unmask]> 12/08/2009 04:55 PM To <[log in to unmask]> cc "'TechNet E-Mail Forum'" <[log in to unmask]> Subject RE: [TN] Storing of Copper Sheets But will push the time frame out right? John Burke (408) 515 4992 From: [log in to unmask] [mailto:[log in to unmask]] Sent: Tuesday, December 08, 2009 2:51 PM To: John Burke Cc: 'TechNet E-Mail Forum' Subject: RE: [TN] Storing of Copper Sheets Hi John - yes, if that deep freeze is in liquid nitrogen - otherwise diffusion is still going to progress on its merry way to the same end result. Standard freezing temperatures will not slow down the diffusion process enough to prevent degradation. Dave "John Burke" <[log in to unmask]> 12/08/2009 04:48 PM To "'TechNet E-Mail Forum'" <[log in to unmask]>, <[log in to unmask]> cc Subject RE: [TN] Storing of Copper Sheets Unless of course he stores them in the deep freeze........ John Burke (408) 515 4992 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman Sent: Tuesday, December 08, 2009 2:40 PM To: [log in to unmask] Subject: Re: [TN] Storing of Copper Sheets Hi Bob - unfortunately you are going to lose the solderability of those sheets somewhere in the 6-12 month time frame depending on which immersion tin formulation you are using and due to diffusion issues will lose the solderability of the sheets on a permanent basis somewhere in the 12-24 month time frame depending on the thickness of the immersion tin plating. You may be able to "reactive" the surface for some other operation but you will need to somehow make sure the surfaces to not passivate (aka oxidize) preventing the next process operation. My recommendation is talk to your favorite plating supplier. Good Luck. Dave Hillman Rockwell Collins [log in to unmask] bob wettermann <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 12/08/2009 11:11 AM Please respond to TechNet E-Mail Forum <[log in to unmask]>; Please respond to bob wettermann <[log in to unmask]> To [log in to unmask] cc Subject [TN] Storing of Copper Sheets Dear Technetters: If you planned on storing 10z copper sheets with a bright immersion tin coating for several years in 24 x 24" sheets-how would you do it? We have several internal opinions from interleaving of saver paper to moisture barrier bags to other types of bags. Thanks! Bob Wettermann PH 847-767-5745 --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------- 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 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