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August 1999

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Subject:
From:
John Brewer <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 25 Aug 1999 11:04:36 -0400
Content-Type:
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Phil mentioned:

>i really doubt that your customer would accept your nitric acid, acetic
acid
>cleaning process without data to backup your capability to clean up the
>cleaner.  i mean this stuff will eat up copper.  nothing like flying
around
>in an aircraft while residues are eating away at your electronics.

Ouch! Yes, I'd recommend against this too. In a previous life, dipping a
PDP11 module (ok, so it was an OLD previous life!!) into a weak acid
solution
to clean off some organic flux residue resulted in electro-plating shorts
between
the leads of cerdip parts.  The boards had come right off test, and likely
had
charge still in various caps, etc... I delidded the parts, sheared the bond
wires
and low resistance shorts still existed between pins.

A 5% visual reject rate became a 80% functional failure rate, and we ended
up scrapping the entire run. (the manufacturing engineer who had come up
with this idea was VERY popular for a couple weeks!!")

The moral of the story was "beware of getting any acid solutions anywhere
near a populated PWB"...

John

John Brewer
Component Engineering Supervisor
Square D Company
[log in to unmask]

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