Hi everyone,

I sent the message below last week and I didn't get any response to the
questions.  I'm not even 100% sure that anyone received the e-mail, and I
hope that everyone understands that I'm not saying that I think mixing is
OK, that's why I'm asking.  I'm new to SMT and I want to understand
completely the ramifications to mixing, if any.  Thanks.


I believe this topic has come up on the technet, so I apologize if this is a
duplicated question.  I need to know what the proper procedure for handling
solder paste.  Right now we mix solder paste that has been used all day(4-8
hours) with new solder paste.  I know it has been said that one should not
do this.  But, with our process I do not see any quality issues(I think)
that is a direct result of this mixing.  So, that leaves me with several
questions:

1. What will the mixing of old and new do to a solder joint?

2. What tells me(visually) that mixing is a bad thing?

3. What is everyone else doing with their process?

4. Does anyone measure the amount of solder they use so that they have
minimal left over at the end of the day?

5. If the old is kept separated from the new, can it be used then?

6. What does everyone do with the used solder paste?

Any response would be greatly appreciated!



Jim West
Manufacturing Engineer

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