When to trash the solder paste

I concur with Chunks.

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I have instituted a policy that probably seems a little extreme to some, but is worth the cost in my eyes. Once a jar of solder paste is opened, it must be thrown away at the end of the work day (Properly discarded, of course). We use the small 250mg jars of paste, as to minimize the amount that is lost.

My company, unfortunately, doesn't have a real good climate control system in place, and the SMT line is in the middle of the factory. I found we are often out of the recommended temperature range of the paste we are using (range was 23C-27C). During the day in summer, and in the morning in winter, our SMT defects would spike.

Anyway, I figured I would share my experience with the question you have at hand.

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