Ron
You need to calculate how much impurity (e.g., gold mixes in with the
solder).  Technically, there is always a decrease in melting point with the
addition of small portions of impurities.  But more impurities will raise or
lower the Tmelt from that point on.  You need to look at the metallurgical
phase diagrams with those metals.  Note: typically gold will increase it
given enough gold.

Carey
-----Original Message-----
From: Hollandsworth, Ron <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Tuesday, October 26, 1999 6:51 AM
Subject: [TN] Subj: Change in Melting Points


>Good Morning TechNet
>I have a question concerning the melting points in the soldering process.
>63/37 (Eutectic solder) has a melting point of 361 degrees F.  I think that
>is like close to 183 C.  In a reflow or handsoldering operation you are
>applying a specific amount of solder or solder paste on a pad.  Now, here
is
>the question, does the melting point of the solder joint, say for a repair
>or rework situation, does the melting point rise above that 361F/183 C?
>That 63/37 has now been mixed with perhaps gold or something else.  This
>question was ask this morning and my reply was that yes it would seem like
>the eutectic point would rise.  There are those of you TechNetters out
there
>that thoroughly understand how mixing metal A with metal B and what the
>result would be.  Hope this is not to crazy a question.  Any additional
>comments on like Silver melting point and melting point in a rework
>situation would also be appreciated.
>
>Thanks
>Ron Hollandsworth
>[log in to unmask]
>
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