We see that type of failure rather often from various customers. It's defiantly has nothing
to do with Black, as it's a "Brittle Fracture{ type of failure seen in
solder joints.

It's normally caused by excessive flexural deformation of a board
(fast cooling component warpage, mishandling etc.).   In that specific
case I think the presence of Ni foot acted as a stress concentrator
facilitating cracking.

I think close up SEMs of those areas might show the p[resence of
microcracks
  

-- 
Best regards,

Vladimir Igoshev. PhD                          mailto:[log in to unmask]

SENTEC Testing Laboratory Inc.
11 Canadian Road, Unit 7.
Scarborough, ON M1R 5G1
Tel: (416) 899-1882
Fax: (905) 882-8812
www.sentec.ca

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