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July 2001

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From:
Mike Fenner <[log in to unmask]>
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Date:
Wed, 11 Jul 2001 15:50:51 +0100
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Suggestion: If you feel so uncomfortable with this long period what you
might want to do initially is to pull a sample every 4 weeks or so but only
send every third or fourth or whatever for analysis. Then if you do see a
big change you can go back and analyse the intermediates to see when it
happened. "Expired" samples can be returned to the pot. You can then
increase the analysis period until you get a measurable change or to six
months or whatever with confidence.

Mike Fenner
Indium Corporation of Europe
T: + 44 1908 580 400
F: + 44 1908 580 411
M: + 44 7810 526 317
W: www.indium.com


-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Graham Collins
Sent: Wednesday, July 11, 2001 3:10 PM
To: [log in to unmask]
Subject: Re: [TN] Wave solder pot analysis


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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