Hi,
In the early days of SMT, many people tried lower melting point temp solders
on the second side.  It is common practice now to use the Sn/Pb eutectic on
both sides relying on surface tension to hold the components.  I personally
do not know of anyone using 2 different melting point solders on
double-sided boards these days.  In order to attain lower melting points,
one must use a bismuth-containing alloy.  Customers were not happy with the
less than shiny joints.

Chris Christian
Indium Corporation of America

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Jerry Mosur
Sent: Wednesday, February 13, 2002 10:09 AM
To: [log in to unmask]
Subject: [TN] Reflow Process


Hello,

As a part of our preparations to set up an internal SMD line, I would like
to get your opinion on the following topic.
What are the problems, if any, associated with reflowing the double sided
SMT board using solder paste with different melting points for top and
bottom.
Is this a fairly common process?
If not what would you recommend as a best assembly process for double sided
SMT boards?


Thanks in advance,

Jerry

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