Bob, I'm a little confused on your question. (OK OK--enough with the
confusion snickers. This is confusion over and above my normal level.)
 
IPC generally uses the term Printed Circuit Board (PCB) "fabrication" to
relate to building of bare boards and PCA for boards that have been
"assembled." Your additional text centers around solder connections and
operations on the board so I suspect you are referring to assemblies.
 
IPC's DPMO committee spent significant time at a number of meetings to
reach consensus on the definition and use of DPMO rather than the
undefined PPM. As a result, DPMO is specifically defined in IPC-7912 and
IPC-9261 but PPM has general use definitions that are not the same from
user to user. The term PPM probably has wider historical use and some
users of the term are applying the same meaning as DPMO. In discussion
with Bob Willis of the SMART Group in the UK, their use of PPM follows
the 7912/9261 DPMO meanings. 
 
Having said that, there are two standards in fairly wide use. Both of
these standards use J-STD-001 and IPC-A-610 to establish defect lists.
Neither document tracks causative actions--the solder connection was
defective because too little solder, poor wetting, bridging, etc.
Regardless of the cause, it's counted as a defect. IPC-7912 defines
component, placement and connection opportunities and defects as
measured AT THE END OF THE ASSEMBLY PROCESS or AT INCOMING INSPECTION BY
THE END USER. IPC-9261 provides the tools to develop DPMO of EACH
ASSEMBLY PROCESS and to develop projected yield figures for the overall
assembly.

Jack Crawford
Director, Certification and Assembly Technology
[log in to unmask]
847-790-5393
fax 847-504-2393
  

-----Original Message-----
From: bob wettermann [mailto:[log in to unmask]] 
Sent: Wednesday, October 22, 2003 7:11 PM
To: [log in to unmask]
Subject: [TN] Board Shop Outgoing QC Measurement Suggestions


What is the the most common practice for measuring the outgoing QC
levels of a PCB fabrication facility? Are ppm defect rates used? If so
how are they practically measured-by the number of solder joints, the
number of operations performed per board or...?
 
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BWET


Bob Wettermann
PH 847-767-5745

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