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Date: | Fri, 24 Jan 97 04:42:15 cst |
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Hi Gaby - You are not going to like this but the cracking phenomena
you are seeing has been documented and is going to be a problem! The
NCMS has/is completing a VERY large study on Lead-Free solder alloy
evaluation. They covered a huge amount of work - everything from cost
analysis, manufacturability and several flavors of solder joint
reliability investigations. I am not allowed to give out specific
details but they did find that with some of the Sn/Pb/Bi alloys that
on thru hole technology assemblies due to solidification physics that
cracking occurs. They will be publishing a portion of this data at the
TMS meeting in Orlando in February and at the IPC Expo in March. There
is some really neat data (well, from a metallurgist standpoint anyway)
going to be coming out of this effort. I suggest you contact Jerry
Rosser at Hughes (or is it Raytheon now?) for more info. His email is
[log in to unmask] . Good Luck.
Dave Hillman
Rockwell Collins
[log in to unmask]
______________________________ Reply Separator _________________________________
Subject: Reflow Soldering of PTH Connectors
Author: [log in to unmask] at ccmgw1
Date: 1/23/97 7:35 PM
Hello,technetters!
We perform double reflow on boards populated with SM LEDs on one side
and on the other side SMCs and PTH connectors.
In order to prevent the LEDs to go twice through hgh temperature
profiles -the second one being even loger-we tried to use a solder
paste with a lower melting point:Sn43Pb43Bi14 which is not eutectic.
The cross section of the pin in hole showed some solder voids-which
were present also when using Sn63 paste and are accptable from our point
of view-but also cracks which originated from them along the pin or
along the hole wall.Our boards are 0,1microns gold plated.
Could anyone explain why it happed and give us some advice?
Gaby
P.S.Thanks to CONDOR and DAVE HILLMAN for their former replies!
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