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December 2009

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Subject:
From:
"David D. Hillman" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Tue, 8 Dec 2009 16:58:47 -0600
Content-Type:
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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]>


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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

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