Hi Lou
We changed to twice a year from monthly.  We did this about a year ago, and have not had concerns with it.

I guess the big thing you need to feel comfortable is the likelihood of this causing problems.  We monitor two solder pots, and the wave solder machine.  In the 10 years monitored we've never been over the limits, and there is enough data that I'm comfortable we would see a trend in time.  Now, if the use of these pots change dramatically (e.g. if we start tinning a lot of gold leads) then I will worry.

So - my recommendation:
If you have reasonably stable usage patterns, and good history, then 6 month intervals is fine.  If your usage varies dramatically , or you have had instances where it's gone from fine one month to bad the next, then stay with what you are comfortable with.

regards

Graham Collins
Process Engineer, Litton Systems Canada, Atlantic Facility
(902) 873-2000 ext 6215

>>> [log in to unmask] 07/11/01 10:54AM >>>
TechNetters, I'd appreciate comments on contaminant analysis of a wave
solder pot.  We had been sending a sample out for analysis (type "C" I
think it is, by the mil spec) once per month.  Now the solder supplier is
telling me that once every six months is more than enough.  I've been
taking the contaminant data and plotting Q charts (for short-run SPC the
modern way, as I've been mentioning in this forum) with the monthly data.
 What has been your practice and recommendation?

At the moment, it is hard for me to feel comfortable with a twice-yearly
analysis of what seems to me to be an important material in our
manufacturing process.  Lou Hart

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