Hello Earl,
did you know that english 'earl' comes from scandinavian 'jarl' which does not mean what it means today, but a 'clan head'. You are seemingly that..he-he.
Cleanliness..standards..norms..SIR..this and that philosophy..I bow deeply in adoration, but there is one tricky area: dirty spots. You can take (best) board out of machine and test and lean back, wonderful <x ug/sq, but in practice you can oftenly find hidden microspots which are predistinated caries cells. E.g. active flux residues under chip caps or under part of a BGA or similar not-easily-auto-inspected spaces. We have seen excellent boards that have been acceptable in ug/sq point of view, but after damp heat tests we have been shocked to see LOCAL corrosion, maybe just some sq mm or less, but enough to cause function failure. I feel that the overall contamination is not such a threat as these microcells. Speaking outdoors parts of cause.
Notice, I'm not against the from-whole-board contamination weight, we use it oftenly, but the (hidden) microcontaminations are oftenly forgotten. All people yawn? Sorry, I'll jump out here...
Ingemar Hernefjord
Ericsson Microwave Systems
-----Original Message-----
From: Earl Moon [mailto:[log in to unmask]]
Sent: den 9 augusti 2002 06:14
To: [log in to unmask]
Subject: Re: [TN] Board cleanliness
Hell Bev, you need a little more fire and brimstone in your life. I take a
bunch every morning for breakfast on my Cheerios, or is that Wheaties?
If we want to go back a ways, the now defunct MIL-P-28809 said something
like 2 megohms/cm, or something to that effect concerning assembled board
cleanliness. Therefore, the axiom was use only DI water exceeding that
requirement to ensure the cleanliness issue was resolved.
I just want to know bare board cleanliness requirements now. I also would
like to know how to make this information a requirements in my master
drawing notes and what document to reference. That document doesn't seem to
be 600 or 6012.
Earl
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