Electronics Forum | Thu Jul 27 07:50:35 EDT 2006 | davef
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Electronics Forum | Mon Jul 24 11:35:42 EDT 2006 | Jimk@ics-inc.org
We have experienced a problem with tin leaching or discoloration of lead terminals on random parts on solder side of a paste/paste operation. The profile has been used on previous production runs and there doesn't appear to be any heat damage to othe
Technical Library | 2014-06-23 14:50:52.0
It was unusual to see chip terminations change colors when tin lead solders were used but with the introduction of lead free reflow soldering and the corresponding increases in reflow temperatures terminations are now changing colors. Two conditions are present when reflow temperatures are increased for lead free solder alloys that leads to discoloration. Reflow temperatures are above the melting point of tin (Sn MP is 232oC). Air temperatures commonly used in forced convection reflow systems are high enough to both melt the tin plating on the termination allowing it to be pulled into the solder joint due to solder joint liquid solder surface tension leaving behind the exposed nickel barrier. Now those metal oxide colors will be visible due to high air temperatures during reflow.
