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January 1997

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Tue, 23 Jan 1996 23:43:25 +0000
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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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