Peter,
You've asked good questions but unfortunately there aren't any good
answers. One can take an OSP coated board or part of a board and
analyze the extracted OSP and then back calculate what the average OSP
thickness was but you won't know if every location was covered with the
average thickness or you could use sophisticated surface analysis tools
to examine the coating at various locations but that is as you say hit
or miss. These are some of the reasons users moved away from OSP (i.e.,
you can't readily tell if all features are coated and you don't know if
they are solderable until you assemble the boards and see how they
assemble.
Regards,
George
George M. Wenger Andrew Corporation
40 Technology Drive, Warren, NJ 07059
(908) 546-4531 [log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Peter Verbiest
Sent: Friday, March 26, 2004 7:31 PM
To: [log in to unmask]
Subject: Re: [TN] Measuring OSP in PTH's
Thanks Mike,
We are seeing inconsistencies in hole fill during wave solder on a card
that
was previously immersion Ag finished and yielded minimal hole fill
problems.
It is true that we may be able to overcome the inconsistencies by
process
changes (i.e. selective pallet redesign, different fluxes/preheat
settings,
etc.) but first we would like to understand;
1. Is OSP uniformly coating the inside of PTH barrels on virgin PCBs and
to
what extent is PCB thickness and/or hole size affecting the coating
thickness.
2. Is CuO present in barrels in virgin cards. (Could perform x-sections
and
analyze but this could be hit and miss.)
3. Is CuO present after 1 SMT reflow, 1 aqueous wash, 2 SMT reflows, 2
aqueous washes, etc.
Thanks all,
Peter
-----Original Message-----
From: Barmuta, Mike [mailto:[log in to unmask]]
Sent: Thursday, March 25, 2004 3:25 PM
To: 'TechNet E-Mail Forum.'; 'Peter Verbiest'
Cc: Barmuta, Mike
Subject: RE: [TN] Measuring OSP in PTH's
Peter: You may want to check the TechNet archives there's a lot of
information on OSP coatings.
The coating itself is a reaction mechanism with the exposed surface
copper
of the PCB. It forms be a uniform thickness on the holes and surfaces
and is
pretty much self limiting. It is not like a paint or even a rosin type
coating that would have various types of build-up thickness at edges,
lips,
large flat areas, etc. Where viscosity and topography can affect the
deposit
thickness.
It is possible that extremely small vias may not have the same amount of
coating due to solution transfer and rinsing. However I've never found
that
to be a problem.
What exactly is it that you are trying to determine? Are you having
process
problems? There are many things that can impact this and ways to
measure,
test and overcome them depending on the situation.
Regards
Mike Barmuta
Staff Engineer
Fluke Corp.
Everett WA
425-446-6076
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Peter Verbiest
Sent: Thursday, March 25, 2004 1:18 PM
To: [log in to unmask]
Subject: [TN] Measuring OSP in PTH's
Hi All,
I have a need to better understand the distribution of OSP (i.e. Entek
Cu-106 A) along the wall surfaces of different size PTH's.
I would appreciate any literature, ideas, or recommendations on
approaches
to collect such information.
Thank you,
Peter Verbiest
Jabil Circuit
San Jose, CA
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