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A Novel PPF Technique--Sn-PPF: Effects of In-Situ Formation Cu-Sn-Ni Intermetallic Nano-Layer on Electronic Packaging Performances

Published online by Cambridge University Press:  26 February 2011

Lilin Liu ,
Ran Fu ,
Deming Liu  and
Tongyi Zhang
Lilin Liu
Affiliation:
llliu@ust.hk, Hong Kong University of Science and Technology, Department of Mechanical Engineering, Clear Water Bay, Kowloon, Hong Kong, N/A, China, People's Republic of
Ran Fu
Affiliation:
rfu@asmpt.com, ASM Assembly Automation Ltd, 4/F Watson Centre, 16 Kung Yip St., Kwai Chung, Hong Kong, n/a, China, People's Republic of
Deming Liu
Affiliation:
deming.liu@asmpt.com, ASM Assembly Automation Ltd, 4/F Watson Centre, 16 Kung Yip St., Kwai Chung, Hong Kong, n/a, China, People's Republic of
Tongyi Zhang
Affiliation:
mezhangt@ust.hk, Hong Kong University of Science and Technology, Department of Mechanical Engineering, Clear Water Bay, Kowloon, Hong Kong, n/a, China, People's Republic of
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Abstract

A novel preplated leadframe (PPF), i.e. Sn-PPF, is developed by electrodepositing a 3∼4nm thick Sn layer between the Cu base leadframe and the Ni plating. The nano-thick intermetallic compound (IMC) layer forms automatically through interdiffusion and reaction between Cu, Ni and Sn. High resolution transmission electron microscopy (HRTEM) observation reveals crystallography relationship between the IMC and Cu base. A drastic reduction of Cu out-diffusion is confirmed by an EDX based oxidation test carried, indicating a significant enhancement in the protection of the leadframe against oxidation and corrosion attack. The Cu diffusion coefficients in the IMC layer were estimated to be about at 250°C and m2/s at 300°C. Results of the wire pull test, the solderability test and the bending test exhibit Sn-PPF's quality with a Ni layer less than 200nm satisfying industrial requirements.

Keywords

barrier layerdiffusiontransmission electron microscopy (TEM)
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 968: Symposium V – Advanced Electronic Packaging , 2006 , 0968-V03-08
Copyright
Copyright © Materials Research Society 2007

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References

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