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
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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]>
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12/09/2009 07:24 PM
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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
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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
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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
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[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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