Mornin' Bob,

Below is a pretty interesting paper that was done by Dr. Colin Drury
called; "Visual Inspection Reliability: What we know and why we need to
Know it."

http://www.hf.faa.gov/docs/508/docs/drury_doc.pdf

Although this paper is geared towards aircraft airworthiness inspection,
I think it's pertinent because the factors involved in visual inspection
is pretty much the same no matter what one is inspecting.

-Steve Gregory-

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of bob wettermann
Sent: Thursday, January 11, 2007 5:35 AM
To: [log in to unmask]
Subject: [TN] Manual Visual Inspection of PCB Assemblies

Ladies and Gents:

Perhaps you can shed some light on an issue I am sure many of you have
faced in the prototyping arena. This issue has to do with the
expectations one should have wrto to "catching" defects (missing, out or
rotation, solder joint problems, etc) for ultra low volume (10 or less
finished assemblies) or prototype PCB assemblies.

We have internalized that only 80 % (on a good day) of the board is
actually inspected  by even the best of QC inspectors. That  leaves 20%
of the board uninspected and one should come to expect, in the absence
of paying/having time  for in-circuit or functional testing, defects to
occur. This is just one of the downsides for building low  volume
(usually fast turn) PCB assemblies. Do you agree?

 Does anyone know of any round-robin testing in our industry that has
helped quantify or document the effectiveness of manual inspection? Has
a specific testing task force ever investigated this issue? Is there a
general industry need for such?

Regards

Bob Wettermann


Bob Wettermann
PH 847-767-5745

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