We think we use the most robust immersion tin but have problems after
one thermal pass - can you tell me off line what tin chemistry you are
using. Thanks. Steve Kelly
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dave Hillman
Sent: Friday, June 21, 2002 10:54 AM
To: [log in to unmask]
Subject: Re: [TN] Immersion Tin
Hi Guy! Steve and I were on the same page for SERA for surface finish
analysis and using other techniques such as CVS, titration, AA, etc. for
plating bath chemical parameter analysis. The SERA system can be setup
in
such a manner as to "drill" through some of the surface finishes to
characterize the intermetallic species beneath a plated surface. My
personal preference is to use XRF to characterize the plating thickness
(using good calibration standards) and use SERA to characterize the
plating
surface characteristics. But there are a number of SERA users who are
very
successfully using the "drill" method on intermetallic characterization.
The Rockwell Collins experience with immersion tin is that there are
some
immersion tin chemistries which perform well and some which perform
poorly
in terms of multiple reflow robustness. It is very important to
characterize an immersion tin surface finish in terms of your own
manufacturing process expectations and not just run a standard "bake"
test.
You would be amazed at how many adhesive cure bakes can creep into an
assembly process flow in addition to the number of passes through a
reflow
oven.
Dave Hillman
Rockwell Collins
[log in to unmask]
"Guy Ramsey" <[log in to unmask]> on 06/21/2002 06:25:14 AM
To: "TechNet E-Mail Forum." <[log in to unmask]>,
<[log in to unmask]>
cc:
Subject: RE: [TN] Immersion Tin
I think you're correct; Steve was thinking of a different tool.
Two reflows then wave . . . HUMMM
I can see two reflows then selective . . . AHHH
But Dave, Ioan seemed to be having trouble after reflow. If the problem
is
formation of unprotected IM, would in-coming SERA predict the process
problem?
SERA attempts to measure oxide species and thickness not the actual tin
thickness.
More importantly, and based on your experience, would you expect IT to
perform well in a multiple reflow process sequence?
Wasn't this one of the big complaints about OSP?
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of Dave Hillman
> Sent: Thursday, June 20, 2002 5:03 PM
> To: [log in to unmask]
> Subject: Re: [TN] Immersion Tin
>
>
> Hi Steve! Sorry but I have to disagree with you. SERA is a tool which
can
> be used to extensively characterize a variety of surface finishes on
> printed wiring boards and any other surface that can be tested within
the
> SERA equipment configuration limitations. I believe you may be
confusing
> SERA with ECI's CVS instrumentation. The CVS equipment measures
certain
> plating bath chemistry parameters. The SERA equipment is similar to
Auger
> spectroscopy in analyzing surface finishes. Rockwell Collins has been
> successfully using SERA since 1991 in a wide variety of applications
(keep
> in mind I'm a bit biased on this subject - Rockwell Collins was
heavily
> involved in the development of the SERA equipment).
>
> Dave Hillman
> Rockwell Collins
> [log in to unmask]
>
>
>
>
> Steve Kelly <[log in to unmask]>@ipc.org> on 06/19/2002 01:13:02 PM
>
> Please respond to "TechNet E-Mail Forum." <[log in to unmask]>;
> Please respond
> to Steve Kelly <[log in to unmask]>
>
> Sent by: TechNet <[log in to unmask]>
>
>
> To: [log in to unmask]
> cc:
>
> Subject: Re: [TN] Immersion Tin
>
>
> SERA will not help you - it is only a tool to measure tin /copper
> concentrations . We have been running immersion tin for 5 years with
no
> issues but only one thermal excursion is allowed. The tin forms a
> copper/tin intermetallic after thermal. We even silkscreen before tin
to
> eliminate this bake cycle. Regards Steve
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Tempea, Ioan
> Sent: Wednesday, June 19, 2002 12:07 PM
> To: [log in to unmask]
> Subject: Re: [TN] Immersion Tin
>
> Hi Tony,
>
> we experienced poor wave soldering after 2 reflows with immersion tin.
> So,
> please give me a few hints on SERA. Is it a test that the board house
> will
> do, or it has to be at our incoming? Does it imply additional charges?
> Where
> can I read more?
>
> Thanks,
> Ioan
>
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