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August 2005

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Subject:
From:
Paul Baine <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Fri, 12 Aug 2005 11:30:17 -0400
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text/plain (43 lines)
Hello all,

I have not used this forum for a few years so I hope I'm doing this
right.

I have a question re calculation of defect percentages for PCB
Assemblies.  The old MIL-STD-2000 standard defined a "defect
rate" as the number of observed defects divided by the "normalizing
number".  The standard requires calculation of the following:

(1) an Assembly Defect Rate, which is the assembly defects
divided by the normalizing number, where Normalizing Number is
(total no. of components, component leads, terminals and wires on
the
assembly plus one for the PWB);  and

(2) a Solder Defect Rate, which is the solder defects divided by the
normalizing number, where Normalizing Number is (total no. of
terminals plus total no. of solder connections).

I cannot find any guideline in J-STD-001 or IPC-A-610 for
calculating defect rates.  I am trying to find some non-time-
consuming method for calculating the Normalizing Numbers.  For
example, would the Solder Normalizing Number just be the total
no. of component leads?

I would appreciate some guidance.  Thanks in advance.

Paul Baine
Q.A. Manager
C-Tech Ltd.
Cornwall, Ontario, Canada

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