Materials 2009, 2(4), 1796-1834; doi:10.3390/ma2041796
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Combined Thermodynamic-Kinetic Analysis of the Interfacial Reactions between Ni Metallization and Various Lead-Free Solders

Electronics Integration and Reliability, Helsinki University of Technology, P.O.Box 3340, FIN-02015 TKK Espoo, Finland
* Author to whom correspondence should be addressed.
Received: 19 October 2009; in revised form: 6 November 2009 / Accepted: 11 November 2009 / Published: 11 November 2009
(This article belongs to the Special Issue Advances in Materials Science)
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Abstract: In this paper we will demonstrate how a thermodynamic-kinetic method can be utilized to rationalize a wide range of interfacial phenomena between Sn-based lead-free solders and Ni metallizations. First, the effect of P on the interfacial reactions, and thus on the reliability, between Sn-based solders and electroless Ni/immersion Au (ENIG) metallizations, will be discussed. Next, the effect of small amounts of Cu in Sn-based solders on the intermetallic compound (IMC), which forms first on top of Ni metallization, will be covered. With the help of thermodynamic arguments a so called critical Cu concentration for the formation of (Cu,Ni)6Sn5 can be determined as a function of temperature. Then the important phenomenon of redeposition of (Au,Ni)Sn4 layer on top of Ni3Sn4 IMC will be discussed in detail. The reasons leading to this behaviour will be rationalized with the help of thermodynamic information and an explanation of why this phenomenon does not occur when an appropriate amount of Cu is present in the soldering system will be given. Finally, interfacial reaction issues related to low temperature Sn-Zn and Sn-Bi based solders and Ni metallization will be discussed.
Keywords: ase diagram; diffusion; lead-free solders; thermodynamics; intermetallic compound layers; electroless Ni

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MDPI and ACS Style

Laurila, T.; Vuorinen, V. Combined Thermodynamic-Kinetic Analysis of the Interfacial Reactions between Ni Metallization and Various Lead-Free Solders. Materials 2009, 2, 1796-1834.

AMA Style

Laurila T, Vuorinen V. Combined Thermodynamic-Kinetic Analysis of the Interfacial Reactions between Ni Metallization and Various Lead-Free Solders. Materials. 2009; 2(4):1796-1834.

Chicago/Turabian Style

Laurila, Tomi; Vuorinen, Vesa. 2009. "Combined Thermodynamic-Kinetic Analysis of the Interfacial Reactions between Ni Metallization and Various Lead-Free Solders." Materials 2, no. 4: 1796-1834.

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