Title

THERMODYNAMIC ALLOY DESIGN OF LEAD-FREE SOLDERS AND THERMODYNAMIC ISSUES OF LEAD-FREE SOLDERING IN ELECTRONIC PACKAGING

THERMODYNAMIC ALLOY DESIGN OF LEAD-FREE SOLDERS AND THERMODYNAMIC ISSUES OF LEAD-FREE SOLDERING IN ELECTRONIC PACKAGING

Authorship

JEONG, SANG WON; KIM, JONG HOON; LEE, HYUCK MO

JEONG, SANG WON

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KIM, JONG HOON

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LEE, HYUCK MO

I am this author

DOI

10.5151/2594-5327-2960

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Abstract

Lead-free solders instead of Pb-Sn are required in electronic packaging due to environmental and health concerns over the use of lead. Also, the reliability of the solder joint is strongly affected by type and extent of the interfacial reaction between solders and substrates. Accordingly, the solder-substrate interaction is increasingly important and a deeper understanding of the interfacial reaction between solder and substrate is necessary. A thermodynamic methodology to predict the intermetallic compound (IMC) phase that forms first at the substrate/solder interface during the soldering process has been suggested. By comparing the activation energy for nucleation of individual IMC phases, which is a function of the interfacial energy and the driving force for formation, the IMC phase that forms first is predicted. A thermodynamic alloy design of the Pb-free solders has been made in terms of melting temperatures and phase equilibria. The IMC phase which forms first at the joint has been predicted as the one with the smallest activation energy. The grain morphology of IMC at the solder joint has been explained through the energy-based calculations. The Jackson’s parameter of the IMC grain with a rough surface is smaller than 2, while it is larger than 2 for faceted grains.

Lead-free solders instead of Pb-Sn are required in electronic packaging due to environmental and health concerns over the use of lead. Also, the reliability of the solder joint is strongly affected by type and extent of the interfacial reaction between solders and substrates. Accordingly, the solder-substrate interaction is increasingly important and a deeper understanding of the interfacial reaction between solder and substrate is necessary. A thermodynamic methodology to predict the intermetallic compound (IMC) phase that forms first at the substrate/solder interface during the soldering process has been suggested. By comparing the activation energy for nucleation of individual IMC phases, which is a function of the interfacial energy and the driving force for formation, the IMC phase that forms first is predicted. A thermodynamic alloy design of the Pb-free solders has been made in terms of melting temperatures and phase equilibria. The IMC phase which forms first at the joint has been predicted as the one with the smallest activation energy. The grain morphology of IMC at the solder joint has been explained through the energy-based calculations. The Jackson’s parameter of the IMC grain with a rough surface is smaller than 2, while it is larger than 2 for faceted grains.

Keywords

thermodynamics, lead-free, solder

thermodynamics, lead-free, solder