Brian,
Yes, I consider the bare boards to be very suspect. I have experienced problems in the past with supposed "ready to go, off the shelf" test articles which were bought at a dummy parts source "because it was cheaper and available". As always, we get what we pay for. In this case, I don't even know which PWB fab house built up the bare board or what kind of processes it actually went through.
Phil
-----Original Message-----
From: Brian Ellis [mailto:[log in to unmask]]
Sent: Monday, October 08, 2012 10:40 PM
To: TechNet E-Mail Forum; Bavaro, Phillip @ MWG - TW
Subject: Re: [TN] ION CHROMATOGRAPHY - EXCESS CHLORIDE CONTENT
Don't forget that many epoxies (etc.) contain chlorides, resulting from the pre-polymerisation reaction between epichlorohydrin and sodium hydroxide. It is easy to leach some of this out, especially if the subsequent cross-polymerisation is not stoichiometric.
Brian
On 09/10/2012 02:29, Phil Bavaro wrote:
> 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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