TechNetters,

I would appreciate your help in deciphering a defect we are seeing
across one board after reflow.

The larger solder joints are exhibiting a ring-like structure - there
are a couple of lines in the joint ringed around the part (as if it
cooled at different rates depending on how close the solder was to the
part?).

Also, all of the parts (large and small) have many black "splotches" on
the joints.  Some of them, if you look closely, appear like snowflakes
or leaves of a fern tree.

Any ideas on the cause and suggestions to fix this?

Thanks.

-Steven

Steven K. Lustig
Process Engineer
EMS Technologies, Inc.
Norcross, GA
(770) 263-9200 x4714
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