Steve,
From one anal retentive cleaning fetishist to another, I understand and have
long practiced the philosphy that hand cleaning is NOT acceptable for
shippable hardware. Period. My reasoning is this.
First, enough handling occurs during rework that other contaminats than flux
are on the assembly, with body salts being the most criminal. If I clean the
flux off of U7, but leave a nasty fingerprint between power and ground at a
bypass cap, what have I done!
Second, if I test for these contaminants with my spiffy bulk ionic
contamination tester, it will say that there was a fingerprint, or something,
but not where or how concentrated the dirt was. In most cases a few
fingerprints will PASS???
Third, because of the above, a special cleaning is imposed on conformal coated
assemblies immediately prior to the drying, masking, coating operation.
Steve Mikell
SCI Systems
Plant 13
------------------( Forwarded letter 1 follows )--------------------
Date: Thu Sep 03 15:40:54 1998
To: [log in to unmask]
From: [log in to unmask]
Sender: [log in to unmask]
Reply-To: [log in to unmask], [log in to unmask]
Subject: [TN] Cleanliness Experiment/Demonstration Ideas?
Hi Ya'll!!!
I was wondering if anybody has any good Ideas that will graphically show
people the importance of proper cleaning. Let me preface this a little; I want
to come up with some way that will hit home to our rework people that hand
cleaning after touch-up doesn't cut it. There's a couple of operators that I
know that aren't convinced that what they're doing is very detrimental to long
term reliability, otherwise they wouldn't do it. Worse yet, their supervisor
I know, thinks I'm some sort of anal retentive cleanliness freak that's making
much ado about diddley.
I've shared many articles about field failures due to electromigration
with everyone, tried to explain the basic science behind what's happening
when electromigration occurs, but I'm afraid I'm not making an impression
because I still catch operators hand cleaning assemblies that should be going
through the inline cleaner.
I feel that if I had some sort of "show and tell" experiment that I
could run here, and they could see with their own two eyes what goes on with
the residues left from hand cleaning, might be a little more effective to show
them the error of their ways better than me lecturing to them about the evils
of hand cleaning an assembly.
I know that there's probably a few of you thinking; "If I had an
operator that wouldn't follow the processes I set, then hasta la vista
baby...hit the road." Believe me, I've thought about it...but except for this
one issue, they're skilled people. Something else I've thought about at the
same time was something I learned in the Navy, that if you're having problems
with an individual, you don't give them orders to another duty station to get
rid of the problem, because you may see that individual again at your next
duty station still with the same problems. I feel it's the same with the
operators in question, I'd rather try to get rid of the bad habits rather than
fire someone, because here in silicon valley, it's a small world when you work
contract manufacturing...I just might see that operator again at the next
company I work at.
Any idea's any of you have would be most appreciated!!!
-Steve Gregory-
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