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March 2009

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Subject:
From:
Ted Tontis <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Ted Tontis <[log in to unmask]>
Date:
Thu, 5 Mar 2009 16:09:41 -0600
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What is your current incoming inspection process for the flex circuits?
Are you requiring the board supplier to perform 100% electrical testing or
AOI?
	As for the registration issues I think a one up pallet and one
circuit perform better throughout the process (depending on size and
complexity) I am guessing that because you noted that there is a fine pitch
component and gold it is somewhat complex. 
	Do you have your boards numbered so you can verify the location on
the manufacturing array? If so have you noticed a trend they may lead to a
process problem, on the board supplier's side? For example you notice that a
certain number of boards from a specific area print paste and place better
then others?  
	If you think your pallet may be the problem, loose fit, try placing
double sided tape on the PCB and run it through your SMT line. If the board
is shifting you should see the parts drifting or not being placed correctly
on the board.

Ted T. 





Hello All,
I have a question regarding a strange situation regarding reflow
soldering ENIG finish boards.
We have seen a few boards that have what seems to be gold "washing "
down between pads and creating shorts. This seems to come and go. This
is a flex circuit that is placed on a pallet to go through our SMT line.
One other bothersome issue is that we are having difficulty getting
proper solder stencil alignment across all the flexes in the pallet. I
am pushing to have the flex "panelized" from the vendor to increase
positional accuracy but the jury is still out on that.
I suspect these two issues are related. If the solder gets deposited
"off pad"slightly could the washing process be moving some of the gold
in between pads? I attached an example.
Has anybody come across this?
If so, what was the solution?
 
Thanks,
Dave Connitt CID+

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