I would appreciate references to these reports showing tin whiskers
are inhibited by storage above 80 C.  On the one hand that's nice.  On the
other, if the tin coated surface is a copper item to be soldered, I have a
concern about excessive growth of the SnCu intermetallics.  Protracted high
temp storage could make it grow thick enough to inhibit solderability.
Does anyone have references for this?

Thanks,
Kirk Mueller






[log in to unmask]@IPC.ORG> on 10/06/2000 12:34:52 AM

Please respond to "Leadfree Electronics Assembly E-Mail Forum."
      <[log in to unmask]>; Please respond to [log in to unmask]

Sent by:  Leadfree <[log in to unmask]>


To:   [log in to unmask]
cc:
Subject:  [LF] Tin whiskers test - proposal for committment


     Hello,

     It is time and place i think to start to take decisions on that
     whiskers growth test .Most of the world wide experts i guess are
     around that forums.

     Among the results we built and we have seen from others , it is clear
     than hot storage above 80°C will reduce whiskers growth , the best
     test to accelerate a room temperature growth (shelf storage) is to
     store at 50-55°C .
     It is may be not the only test to be performed but it must be
     performed .
     The other option is likely to be a humidity & temperature storage
     test which can range from 30°C60%rH which is about room temperature
     of a clasiic store to 95°C-95%rH recently proposed by a forum member
     form OMRON.

     I suggest to move ahead and each forum member to engage its company
     about the necessity to provide storage data at 50° to 55°C in dry air
     when speaking about whiskers.

     Beside lets open the door for a second or third test conditions on
     which you may need more data to all commit and may even be customized.

     Data must be provided with a maximum length which may be drawn from
     the inspection system : for example no whiskers means no whiskers
     longer than X µm or mils .

     We do need in ST Microlectronics to receive that storage data (at
     50-55°C) from any supplier ( process supplier or assembly
     subcontractor ) when speaking about coatings with less than 5%
     allowing element.

     Please vote on that proposal


     Secondly i propose to vote also on the accepation of the fact that
     reflow tin , tin dipped coatings do not grow whiskers.


     I am sure that base on that poll results a standard can be prepared by
     IPC or other relevant organizations



        best regards

           Luc P.

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