Combined thermodynamic-kinetic analysis of the interfacial reactions between Ni metallization and various lead-free solders

Tomi Laurila*, Vesa Vuorinen

*Corresponding author for this work

    Research output: Contribution to journalArticleScientificpeer-review

    16 Citations (Scopus)

    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.

    Original languageEnglish
    Pages (from-to)1796-1834
    Number of pages39
    JournalMaterials
    Volume2
    Issue number4
    DOIs
    Publication statusPublished - 2009
    MoE publication typeA1 Journal article-refereed

    Keywords

    • diffusion kinetics
    • intermetallic compound layers
    • lead-free solders
    • phase diagrams
    • thermodynamics

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