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January 1997

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Subject:
From:
"Wander, Nicholas G RV" <[log in to unmask]>
Date:
Mon, 27 Jan 97 12:39:00 CST
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The soldering alloy we used here at Unisys, Roseville, MN was the 58%   
bismuth and 42% tin eutectic. The melting temperature is 281 deg. F. We   
used it for soldering a .300 thick, 50-layer board. We used this low   
temperature solder to reduce Z-axis expansion of this extremely thick   
board.

Nick Wander
Printed Circuit Engineering
Unisys, Roseville, MN.

 ----------
From:  [log in to unmask][SMTP:[log in to unmask]]
Sent:  Friday, January 24, 1997 2:38 PM
To:  [log in to unmask]
Subject:  Re: Reflow Soldering of PTH Connectors

Gabe-
Dave Hillman pretty much summed it up.  In general, alloys with Bismuth
(which allows for lower melting and liquidus temperatures, do tend to be
relatively brittle (as compared to good  ol' SnPb.  However, in view of   
the
reliability data, your application may be okay.  A number of years ago,   
if I
recall correctly, Unisys (Roseville) was using a SnPbBi alloy but the
reliability was ample for their application.  My main contact in that   
(now
defunct) group was Mike Buseman who is now with MSL in Roseville, MN.   
 You
might try to reach him or Don Burr (who I believe is still with
Unisys-Roseville) for further details.

Phil Zarrow
ITM, Inc.
[log in to unmask]


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