I am sorry but I don't see the pictures. Not understanding the complete
stack up of your flex but it sounds like you are having a lot of movement
during the vendors processing of the manufacturing panel which in turn gives
the assembly process a headache.

- Small pallets are best when processing type 3 circuits
- You can ask your flex vendor to give you the offsets they used @ drill or
final layer image and use these for your paste stencil.
- I have seen the gold wash between metal and actually stick to the
pre-cured adhesive that is sometimes left behind after etch if using a LF9
type of material. This only happen when we had mass exposed areas like fine
pitch components.

Please update your contact for Jim Mahoney
[log in to unmask]
Thank you, 
Jim Mahoney 
Quick Turn Flex Circuits, LLC 
Applications Project Manager 
P# 603-821-6571 
F# 603-821-5723 
M# 603-305-6250 

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-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dave Connitt
Sent: Thursday, March 05, 2009 3:09 PM
To: [log in to unmask]
Subject: [TN] ENIG Question

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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