Effects of Phosphorus Content on the Reaction of Electroless Ni-P with Sn and Crystallication of Ni-P

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The reaction between electroless Ni-P and Sn, and the crystallization behavior of
Ni-P were investigated to better understand the effect of the P content of the Ni-P
layer. Electroless Ni-P specimens with three different P contents, 4.6, 9 and 13wt.
were used to study the effect of P content and microstructure of Ni-P on the
subsequent crystallization and IMC formation during the reaction between Ni-P and
electroplated Sn. Ni3Sn4 was the major phase formed in all samples heated up to
300°C, which totally transformed into Ni3Sn2 when samples were heated up to 450°C
and the Sn layer was 0.5µm thick. The IMC formed on the nanocrystalline Ni-P
showed stronger texture compared to that formed on the amorphous Ni-P. Both the
IMC thickness and density decreased with the P content in the Ni-P layer and Ni3Sn4
morphologies varied with the P content. Dissolution of Ni into Sn increased with the
P content, which made IMC size in the bulk Sn increase with the P content.

By: Y.C. Sohn, Jin Yu, Sung K. Kang, Da-Yuan Shih, W. K. Choi

Published in: Journal of Electronic Materials, volume 33, (no 7), pages 790-5 in 2004


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