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July 2008

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Subject:
From:
"Stadem, Richard D." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Stadem, Richard D.
Date:
Fri, 18 Jul 2008 09:03:02 -0500
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I agree with Brian.
Ionic testing should be done just after cleaning for a Class C-21,
C-123, or C-212345 assembly, but not just to prevent flux from
hardening. The ionic testing is performed as a process control for the
cleaning operation, and if not done in a timely manner many boards may
be insufficiently cleaned before the problem with the cleaning process
is discovered. This means that teardown, containment and re-cleaning
must be performed on a much larger quantity of "dirty" boards than would
have had to have been done had the problem been immediately detected.
But, yes, any flux remaining on the PWB will likely harden and give
lower ionic testing measurements than if tested immediately after
cleaning for the same amount of polar contaminants.

On the other hand, ionic testing is also used to verify cleanliness to
facilitate conformal coating of clean boards. If the boards are going to
sit around for any length of time it is assumed that they are still
flux-free, but ionic testing may not detect the accumulation of dust,
fibers, etc., thus there is no point in running another ionic test. It
would not be able to detect any of that type of debris anyway. 

Therefore the IPC-HDBK-001 states that cleaning should be performed
immediately after soldering if possible, and "the residue measurement is
done to determine any trends (increasing or decreasing) in residues"
detected. The Handbook, in section 8.3.7.2 states that "the ROSE test
was originally developed as a PROCESS CONTROL TOOL to determine
DAY-TO-DAY process variations for assemblies soldered with (fluxes).

What good does it do you to determine you have a trend 6 months after
the fact? 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
Sent: Friday, July 18, 2008 1:05 AM
To: [log in to unmask]
Subject: Re: [TN] Question on Timeliness of J-STD-001D Ionic
Contamination Cleanliness Testing

This is just another example (all too common in our industry) where
rigid adherence to standards negates common sense.

Ask yourself what ionic contamination testing is for. Is it a process
control for your soldering/cleaning operations? Is it an insurance
policy for the correct application of conformal coating? If the answer
to both questions is yes, then, if the two operations are spaced in
time, you must do it twice, not once (on different boards!!!!)

Brian

- bogert wrote:
> July 17, 2008
> 
> J-STD-001D, paragraph 8.3.6 requires that, if cleanliness testing is 
> mandated, the testing must be performed after final cleaning (i.e., 
> prior to conformal coating).  We have an OEM who performs cleaning 
> within 1/2 hour after wave soldering.  The OEM also does post hand 
> soldering after wave soldering and does local cleaning of the hand 
> soldered joints in max 1/2 hour after soldering.  However, several 
> days or weeks may pass between the wave soldering and hand soldering 
> operations before conformal coating is done.  The OEM does the 
> cleanliness test just prior to conformal coating as is mandated by
> J-STD-001 since the cleaning after hand soldering is the "final 
> cleaning operation".
> 
> My question is since the cleanliness test is not done until several 
> weeks after wave soldering/post wave soldering cleaning was done, will

> the ionic cleanliness testing mandated by J-STD-001 (standard 
> instrument test like Omegameter) be caple of detecting ionic
contamination?
> 
> Seems to me that if the cleaning process is having problems, harmful 
> Type M or H flux residue, if not completely removed by the cleaning 
> process, may solidify to the extent that the DI water/Alcohol 
> cleanliness test may not be capable of dissolving the hardened residue

> precluding detecting ionic contamination.  Is this a valid concern or 
> not?  Is there any data that shows the ability of the test equipment 
> to detect ionic residue over time since cleaning?  Do we need to make 
> any changes to J-STD-001, paragraph 8.3.6 based on my question? If so,

> please propose recommended wording for the change.  Thanks for your 
> support.
> 
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