In a message dated 98-03-10 17:36:16 EST, you write:

<< Has anyone any information on barrel cracking associated with the use of
 electroless  nickel (EN) under a gold finish. We have a problem with 0.3 mm
 via's in FR4 multilayer boards cracking after thermal shock at 260°C. We have
 other problems with this board but is there any information on what effect EN
 has under these conditions ? >>

Could you please supply a little more information about these parts that show
barrel cracks?   The standard electroless nickel thickness is 0.1 to at most
0.2 mils in a barrel that should be plated to 1.0 mils or more with copper.
(Or perhaps your spec on vias is to allow as little as 0.5 mils of copper -
please clarify).  The copper electroplate should control the thermal
performance in your case - are barrels cracking if they are HASL or OSP?
Electroless nickel should exhibit a high tensile strenghth on its own - even
if the ductility is not as good as electroplated copper.  Are you saying that
the nickel only is cracking?   The gold should be so thin as to have no effect
on thermal performance.

Dennis Fritz
MacDermid, Inc - Waterbury CT

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