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Factors Affecting the Mechanical Properties of Cu/Electroless Ni-P/Sn-3.5Ag Solder Joints

Published online by Cambridge University Press:  26 February 2011

Aditya Kumar
Affiliation:
aditya@pmail.ntu.edu.sg, Nanyang Technological University, School of Materials Science and Engineering, N4.1-B3-02,, 50 Nanyang Avenue, Singapore, 639798, Singapore, +65 6316 8955, +65 6790 9081
Zhong Chen
Affiliation:
ASZChen@ntu.edu.sg, Nanyang Technological University, School of Materials Science and Engineering, 50 Nanyang Avenue, Singapore, 639798, Singapore
C. C. Wong
Affiliation:
WongCC@ntu.edu.sg, Nanyang Technological University, School of Materials Science and Engineering, 50 Nanyang Avenue, Singapore, 639798, Singapore
S. G. Mhaisalkar
Affiliation:
Subodh@ntu.edu.sg, Nanyang Technological University, School of Materials Science and Engineering, 50 Nanyang Avenue, Singapore, 639798, Singapore
Vaidhyanathan Kripesh
Affiliation:
kripesh@ime.a-star.edu.sg, Institute of Microelectronics, 11 Science Park Road, Singapore, 117685, Singapore
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Abstract

This work investigates the factors that affect the mechanical properties of Cu/electroless Ni-P/Sn-3.5Ag solder joints. For the investigation, solder joints were tensile tested after solid-state aging at different temperatures for various durations. Several factors, such as the growth of interfacial compounds (IFCs), Ni3Sn4 morphology, the accumulation of spalled Ni3Sn4 intermetallic particles at the solder/Ni3Sn4 interface, and the formation of Kirkendall voids at the Ni3P/Cu interface, are found to deteriorate the mechanical properties of the joints. Among all these factors, the formation of a layer of Kirkendall voids at the Ni3P/Cu interface, which is a result of Cu diffusion from the interface, causes the most severe decrease in tensile strength with a brittle fracture at the Ni3P/Cu interface. This layer of Kirkendall voids remains the main cause of brittle failure even after the transformation of the Ni3P layer into a Ni-Sn-P layer.

Type
Research Article
Copyright
Copyright © Materials Research Society 2007

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References

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