TechNetters, 

I've made SPC charts to track tin, copper, gold, and antimony in our wave solder machine.  The operator skims dross from the solder pot every morning.  We send a solder sample the first of each month to Kester for analysis.  Over the past 7 months, there has been a monotonic increase in copper concentration and the past two months have been above the upper control limit.  The copper concentration is still well within spec (0.3%, if I am correct, according to the relevant IPC standard) at 0.14%, but I want to make sure we know what is happening.

Any comments on these observations?  Some years back I had charts for a HASL machine and over perhaps 12 months the semimonthly copper concentration wandered between 0.21 and 0.24 %.

Lou Hart

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