I agree that the "Black pad" issue is used as a ''catch all" for  a multitude
of assembly problems with the ENIG finish.

After the issue of the IPC ENIG specification (IPC-4552) where the  immersion
gold thickness recommended was restricted to 2- 4 micro-inches with  advice
not to exceed 5 micro-inches, and the industry understanding of how the  BP
occurs, incidences of BP have almost disappeared.

As far as P-content of the Ni is concerned, most ENIGs today supply a 6 - 8
% P. Some suppliers also supply P at 8 - 10 %. It is the customers choice
which  way to go. The lower P content has an edge in soldering and the higher has
an  edge on corrosion resistance.

ENIG is the only surface finish where a Cu/Sn intermetallic is not formed.
With ENIG you form a Ni/Sn intermetallic. Assemblers understand the difference
and make the necessary profile adjustment when assembling this finish.

ENIG as BGA surface finish has the advantage over electrolytic plating in
that the part does not need to be electrically connected (bused) for plated. The
 electrolytically plated Ni/Au surface should solder well also, caution  to
limit the gold thickness to stay clear from Solder joint  embrittlement issue.

Best  regards

George Milad
[log in to unmask]
National Accounts Manager  for Technology
Uyemura International Corporation
Technical Center
240  Town LIne Rd
Southington CT 06489
(516) 901 3874 (mobile)
(860)  793-4011 (office)
(860) 793-4020 (fax)

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