Hi Mike - take a look at the following paper "An Investigation Of the
Effects of Printed Wiring Board Surface Finish and Conformal Coating For
Ball Grid Array Assembly" in the APEX 2000 Conference proceedings - it
documents a reliability test sequence which included an immersion tin
surface finish. Good Luck.

Dave Hillman
Rockwell Collins
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"McMonagle, Mike" <[log in to unmask]>@IPC.ORG> on 06/23/2000 09:39:40 AM

Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
      to "McMonagle, Mike" <[log in to unmask]>

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Subject:  [TN] Immersion Tin Suppliers


        I am in the process of evaluating white tin as an alternate surface
finish for our assemblies that contain fine pitch (<20mil) and uBGA
devices,
as HASL provides too many 'challenges' for high yields with such
components.

        I have found that our current stateside suppliers, whom we use for
proto and low volume turns, all farm out the immersion tin processing
portion to secondary vendors. And our current offshore (volume) vendor is
just starting to 'test the waters' with white tin, using the Stannatech
process, also through a secondary vendor.

        As I would like to qualify any evaluation fabs (and future
purchases) from a source that performs their own white tin process
in-house,
I am looking for leads on both local and offshore suppliers who have
internal capability for white tin. Also, any feedback on experiences with
Atotech's Stannatech vs Omikron vs Dexcoat would be appreciated.

        Onward into the fog....

Mike McMonagle
PCBA Process Engineering
Telxon Corporation
(713) 307-2443 Phone
(713) 307-2581 Fax
http://www.telxon.com

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