John Perry sent an email (at the end of my discussion) in preparation for the Apex meetings this past spring. The question he asked was (essentially) what magnification should be specified to inspect boards with.  I am bringing it up before the fall meeting in Las Vegas to get some feedback on my recent experiences and suggestions for 6012.



We purchased two lots of boards (from two different shops) and they both had reduced trace widths.  Of course we did not discover these until surface mount solder inspection - after two units had been fully assembled and tested - and ready to ship to the customer.  Surface mount inspection is not designed to inspect for traces but once you see it you can't ignore it.  And of course surface mount inspection is performed at 10X minimum magnification.

While we were investigating the reason for the escape, we found than both companies have designated their etch operator to also act as the QC inspector.  They are able to do this by 'controlling' their processes and believing only catastrophic failures can get to etch, and the operator will catch all catastrophic failures. My opinion is that inspecting panels at production rates, while also running the equipment, is not practical.

Inspecting boards at final, for in-process defects, is the wrong time to inspect.  In fact many of the items 6012 requires to be inspected (weave exposure, measles, surface imperfections etc)  can only be inspected prior to soldermask application but the only place inspection is required is at final inspection. (Paragraph 3.3)

I would like to propose that a requirement be added that for Class 3 and/or Space Grade that a formal QC, subsequent to etching and prior to soldermask be required. We can haggle about the magnification but I believe 1.75x would be sufficient. This would allow the board shop to inspect relatively quickly (as opposed to requiring an oppressive 10x) and because you are examining the board as bare copper, small defects will stand out.

Following my signature is the original email John sent.

Thanks,
Pete


Pete Menuez
Supplier Quality Engineer
L-3 Communications Cincinnati Electronics
7500 Innovation Way
Mason, Ohio 45040
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513-573-6401 Voice
513-573-6767 Fax









-----Original Message-----
From: John Perry [mailto:[log in to unmask]]
Sent: Wednesday, February 09, 2005 12:30 PM
To: [log in to unmask]
Subject: [IPC-600-6012] IPC A-600 6012 and 2221 task group at Expo 2005


Colleagues,



The D-31b IPC-2221, D-33a IPC-6012, and 7-31a IPC-A-600 task groups will
all meet jointly at IPC Printed Circuits Expo/APEX 2005 during the D-30
Rigid Printed Board Committee meeting taking place on Monday, February
21st from 1:30 pm - 5:00 pm in Room 303B of the Anaheim Convention
Center.



The agenda for this joint meeting is listed below.



In advance of the meeting, please give some consideration to the 3rd
agenda item, as detailed in item 5 of the IPCWorks 2004 meeting minutes
for D-33a/7-31a:



The task groups were asked to consider a rewrite of the magnification
level requirements described in 1.5 of IPC-A-600G and 3.3 of IPC-6012B.
The initial request was to tighten the magnification required as several
board shops witnessed escapes of rejectable product after determining
that the anomalies could not be detected at the initial magnification of
1.75X.  This opened up the larger question of what is the resolution
capability of 3 diopters (1.65X to 1.85X) and 5 diopters (3X).  It was
agreed that there is a need to create a Gauge R&R to determine the
resolution capability of inspection equipment at 3 diopters and 5
diopters to allow for the build of more specific criteria for 3.3 of
IPC-6012C and 1.5 of IPC-A-600H.



An attached .jpg image illustrates the availability of visual inspection
tools that support 5 diopter or greater resolution.  If you have any
feedback on this issue feel free to use this e-mail thread within the
IPC-600-6012 forum - I will collect any feedback for review at the
02/21/05 meeting.



Here is the planned D-30 meeting agenda:



1) Review items addressed for IPC-2221B working draft at the 2005
Interim Meetings in Tempe, AZ



2) Review input from Sun Microsystems relative to spacing boundary for
new measling criteria as discussed in item 3 of the D-33a/7-31a IPCWorks
2004 minutes



3) Review input on resolution capability for visual inspection equipment
at 3 and 5 diopters as discussed in item 5 of the D-33a/7-31a IPCWorks
2004 minutes



4) Review request for clarification/rewording of notation in Table 3-2
of IPC-6012B and Table 4-3 of IPC-2221B relative to reduction of surface
copper wrap



5) Review status of D-33d Via Protection effort towards IPC-4761
guideline release



Regards,



John Perry

Technical Project Manager

IPC

3000 Lakeside Drive # 309S

Bannockburn, IL 60015

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1-847-597-2818 (P)

1-847-615-7105 (F)

1-847-615-7100 (Main)