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April 2007

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Subject:
From:
Wayne Thayer <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Wayne Thayer <[log in to unmask]>
Date:
Thu, 19 Apr 2007 09:15:05 -0400
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Well, it is SAC, so it looked ugly to start with, right?  I believe it
will look even uglier--very grainy with lots of protrusions, but none
long enough to bridge the gap between pins.  Depending on how the layers
in your Polyimide board are held together, your laminate may embrittle
drastically.  The ENIG, if done perfectly, will survive, but if there is
any flaw in the nickel process you will see nice black pad failures.

I would be surprised if the solder joints themselves (ignoring the
black pad possibility) did not survive, but obviously the extremely
large grains they would turn into would be even less capable of
accepting some creep than the SAC was originally.

Perhaps if you did this in vacuum or in nitrogen it would look a bit
nicer when it was done cooking.

Wayne Thayer

>>> [log in to unmask] 4/18/2007 2:38:04 pm >>>
Hi all,
 
Just curious, what would you think that a SAC 305 solder joint on a
SOIC
that was made on a ENIG finished polyimide board would do after
spending
140 - 168 hours at 350 F. ?
 
Just wondering is all...
 
-Steve Gregory-

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