Hello Everyone:

I am trying to design am experiment to study the surface appearance of
solder bumps and its effect on the shininess/dullness of bumps.  One of
our customers recently reported an increased rejection rates at their
placement machine as the dull solder bumps were not recognized.

Although we have not conducted extensive experiments in house to study the
effect of reflow profile, cooling rate and the flow of nitrogen etc., i
would appreciate feedbacks regarding your experience with this issue.

We also rinse our wafer lots with DI water after reflow.  Is there a
possibility of impurities in DI water attacking the surface of eutectic
solder. All of the wafers we bump are near eutectic solder alloy
composition.   The issue of dull solder bumps seems to be a periodic
issue,not surfacing regularly.

I would appreciate your comments on factors responsible for causing dull
bumps.

Regards
Manish

PS I am only refering to the occurence of dull solder bumps after wafer
reflow.  We use a water soluble flux during the wafer reflow.

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