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Wed, 10 Nov 2010 07:58:04 +0100
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Hello technetters.
We have a bad wettability (SnPb process) on some copper ribbons covered by 
a Ni layer and Au layer. These are applied by an ENIG process.
The ribbon no-wet area is located on alongside and edges of ribbons. No 
issue in the centrum area of the ribbon. The ribbons are 3 mm width and 
0.3 mm thick.
The Ni layer and Au layer have the good thickness : 4µm and 0.1 µm. But 
with a SEM analysis we see in the bad area a porous Au. 
At the degolding operation, the area becomes black, the SnPb don't  wet 
and the SEM analysis gives a high presence of Phosporus in that area 
(Qualitative analysis, the P peak is half the Ni peak).
At soldering operation more you try and worse it is.
The manufacturer of the ribbon says the P in the Ni-P bath is 9%.
Question:
I think the cause is a bad control and homogeneity of the Ni-P bath. Is it 
correct or could be another cause as "only"  2/3 of the lot is bad?
After ENIG process, how many P has to remain on the Ni layer ?
Thanks for your answers.

Best regards,
CANTAGALLO Luigi

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