Hi Chris

Here are some of the answers as I see them:

 We thermally stress circuit boards at 550o F (288o C
 ) for ten seconds, referencing test method IPC-TM-650, Number 2.6.8.,
 revision
 C, date 8/97, sections 5.4 - 5.6.
 But how often should we replace the solder ?
 Is there a time constraint or quantity constraint that dictates when
 to replace the solder with new material ?

        Since you are using the solder for thermal stress and not solderability,
there are
        very few constraints on the solder in the pot since it is a heat source and
it's
        composition is not critical to the test.

        If you were also using the pot for solderability testing, you would follow
the
        recommendations found in J-STD-001.

 In addition, is there any information concerning the procedure for
 replacing  the solder in the pot ?
 Is there a percentage of copper that must be added to the 63/37 tin/lead
 solder ? Or some other preparation needed for proper solder flow.

        As for a complete replacement the solder should be molten and we just
        pour it out into another container - very carefully.

        You could also cool the bath and skim off material that solidifys first since
        it will contain contaminates - such as copper and then add additional fresh
        solder.

        The solder should flow very well at 63/37, if the samples are properly fluxed
        prior to floating.


Hope this helps.  Let me know if you need further clarification.

Susan Mansilla
Robisan Lab

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