Lou,
        While not addressing your original question, why don't you just skim
the copper out?  Your SPC chart will let you know when to do this.

Ryan Grant
Advanced Technology Engineer
MCMS
(208) 898-1145
[log in to unmask]


> -----Original Message-----
> From: Lou Hart [SMTP:[log in to unmask]]
> Sent: Wednesday, December 06, 2000 1:03 PM
> To:   [log in to unmask]
> Subject:      [TN] Copper contamination is wave solder
>
> 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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