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Reply To: | (Leadfree Electronics Assembly Forum) |
Date: | Wed, 6 Dec 2006 16:16:18 EST |
Content-Type: | text/plain |
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Hi Gordon,
Methinks there is somewhat of a circular argument going on, and that your
reply was somewhat tongue-in-cheek.
By definition, 'Black Pad' means that there is enough P on the Ni
surface/interface to both turn it [at least partially] dark grey/black and to weaken it
sufficientl to cause brittle interfacial failure [BIF] between the Ni and the
Ni-IMC, when sufficient stress is applied to overcome whatever adhesion
strength exists.
While there are of course other causes for the BIF failure mode, even at the
Ni/IMC interface, if more P can prevent BIF due to 'Black Pad' we are talking
about a different mechanism.
If BIFs are caused by "the board fabricator letting the phosphorus
concentration in the electroless nickel plating bath get too low,' than what results is
not 'Black Pad'—by definition.
Werner
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