Hi Chis,
Are you an assembler or board mfg? In any case it sounds like you got audited by someone who doesn't look at the whole picture but simply wants to satisfy a survey form. As I understand it, mostly the contaminate limits recommended for solder are there to provide us with an outline so as to keep us from having solderability problems. If your solder becomes contaminated such as high levels of copper you should start seeing this in the form of poor quality reflow on the pads or joints. As far as tin /lead ratio, when was the last time you had a failure for this?
As far as the question goes for containment, poor solder quality as far as the joints or pads go would be contained in house by your quality departments and would not be governed by the results of your solder analysis. As far as composition, if you maintained statistical data that showed an ongoing control of the process, there should be no reason to sample daily. Most of us don't have the equipment in house to analyze the solder and the costs of daily testing would be prohibitive. I would recommend that you take and retain daily samples but test monthly. This way if you where to ever have a failure, you could have the retained daily samples tested sequentially until you have determined the date of failure. Then containment would simply be a matter of identifying the lots processed on the days that the solder was out of spec. If the parts have already shipped you could notify customer of your findings.
My guess would be that even if you notified a customer of an out of spec limit , say your tin lead ratio was a little off, but the solderability was acceptable to the customer, they would not be all that concerned anyway.
Just my thoughts,
Ed Cosper
Director Quality Assurance and Engineering
GEI Circuits Inc.
----------
From: Chris_Smith[SMTP:[log in to unmask]]
Sent: Monday, June 01, 1998 7:46 AM
To: [log in to unmask]
Subject: [TN] Solder Sample Testing?
Ladies & Gentlemen,
I am currently working on a schedule for solder pot sampling. The
pots will be tested every 30 days and two samples will be taken from
each pot. This way if one test happens to fail, we can send the other
sample to verify the test. The problem I have ran into is what to do
if it fails. In a recent customer audit I was asked what kind of
containment would we have if the test failed? Since we are using the
ANSI/J-STD-001A there are clearly defined limits that must be met. It
is my understanding that when you test the solder you are testing for
the last 30 days. The problem I have is this. If I test the pot on
1-1-98 and it passes I'm fine. But when I test again on 2-1-98 and it
fails I have a huge problem. Since the last day I can prove the
solder was within limits was Jan, 1 that makes everything suspect bad
material to that date. I can't write the procedure to recall
everything for the last 30 days, I need a different solution. If you
have any information on how your company handles this please let me
know. Please keep in mind, that we must meet the ANSI-STD and any
element out of range is considered a failure to our customer,
regardless if the solder integrity is affected or not.
Thanks
Chris Smith
Manufacturing Engineer
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