Hello Technetters,

I'm a new member to this board, and hope some technetters could void their
opinions and advices on this issues.

We are currently dealing with a 0201 SMT process and have some issues with
a HASL 0201 landpatterns. The HASL PCB has non-uniformed finshed surface,
and results in tombstones and solderballs after the reflow process. We then
switch to Immersion gold 0201 landpatterns and the issues of solderballs
and tombstones went away. The average cost different between HASl and
Immersion gold (7-10 micron)is about 6 - 8 % in cost. Another PCB vendor
introduced us to Immersion Tin (white tin) to reduce the additional cost of
Immersion Gold pads (about 2-5 % cost different between HASl and Tin). We
have used Immersion Gold in many of our prototype products and having
really high yeilds, but we have not try the Immersion Tin pad finished and
wonder if they behave like the Immersion Gold. The vendor also mentioned
that the Tin finished will oxidize and have a shelf life of 12 months.

BTW, We are using "No Clean" process with Convection air oven.

Any technetter has experienced in both pads surface finished ( Gold Vs Tin)
is greatly appreciates.

Tuan Bui
Process Dev Eng
Conexant Systems Inc.

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