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October 2012

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Subject:
From:
Bev Christian <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Bev Christian <[log in to unmask]>
Date:
Mon, 8 Oct 2012 20:09:03 -0400
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Phil,
Very strange.

Has the ROSE tester been calibrated?
Physically what is different between one test sample and the other two?
Were all three test samples ROSE tested together or separately? 
Were they shipped together or in separate bags or even in totally separate
packages?
How far away is your manufacturing facility from the lab?  Next door? Next
city? Next state? 
What are you getting for chloride readings for your blanks?

Bev


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Phil Bavaro
Sent: Monday, October 08, 2012 7:30 PM
To: [log in to unmask]
Subject: [TN] ION CHROMATOGRAPHY - EXCESS CHLORIDE CONTENT

We have some results that have left me puzzled.  We are processing the
IPC B-52 test PWAs using water soluble paste/flux and we can pass the
ROSE test (of course) and the SIR test, but fail the IC test for
excessive choride anion content.

Here is what baffles me.....our control sample is similar and worse than
the test samples.

There seems to be some documentation that the chloride ion might be
related to mishandling and/or soldermask not being properly cured but I
don't have any experience with this test result so I am not sure how to
respond to that (hopefully Terry will chime in on this).  We processed
all the samples using the proper gloves and bags and doubt that we
contaminated them.

We are trying to meet the requirement of 0.9 micro-gm/cm-cm maximum and
our failing control sample is 3.36, one test sample is 4.67, and the
other two samples are running at .91 and .90.  What value for chloride
anion content does a normal WS process yield? Are these numbers way out
of range for normal test results or is chloride always a pesky result?  

I am looking for the answer to the question "is this really a problem?"

The control sample was washed but did not have any paste applied to it
at all.  The test samples were run through the full assembly reflow
process then cleaned and Rose tested before shipment to the lab.

All the rest of the results for the IC test are passing so I don't know
quite how to proceed from here.  

My current plan is to run another set of tests with more than one
control sample, and then to simulate various phases of clean (IOW barely
cleaned, half cleaned, and then a couple of fully cleaned samples).  As
I am not really familiar with IC test results, I want to see the what
the constituents of the "dirt" really look like from an IC test
perspective as well as repeat the previous test results.

One item I have noted is that we did not have our chosen board supplier
build these boards but instead bought these off the shelf from one of
the dummy component suppliers.  But the thought was that as long as they
were cleaned using our normal process, they should be acceptable.
These particular test samples use FR4 and not the high Tg polyimide that
most of our PWBs are built from.

Any comments on this would be appreciated.

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