Kinetics of intermetallic compound layers and Cu dissolution at Sn1.5Cu/Cu interface under high magnetic field

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The kinetics of intermetallic compound (IMC) layer and Cu dissolution at Sn1.5Cu/Cu interface under high magnetic field was experimentally examined. It is found that the IMC layer growth is controlled by flux-driven ripening process. The high magnetic field promotes the growth of IMC layer, retards the dissolution of Cu substrate, and decreases the content of Cu solute at the liquid–IMC interface front. Based on the experimental results, it is considered that the magnetization induced by magnetic field promotes the ripening process for IMC layer growth. The Lorentz force dampening the convection and magnetization decreasing the Cu solubility limit can retard the Cu dissolution and change the solute distribution at the liquid–IMC interface front.

I. INTRODUCTION

When two kinds of metals are attached to each other, stable intermetallic compounds (IMCs) may be formed as layers at the interface in the diffusion couple as a result of reactive diffusion. The formation and growth of IMC layers is a key issue to confer desirable material performances in many processing techniques, such as hot dipping and soldering.1,2 Understanding the IMC growth mechanism in ambient conditions, such as in the temperature, electronic, and magnetic fields, is therefore essential for controlling material properties. With the recent developments in high magnetic field technology, their application for the interfacial mass transfer control has attracted the attention of researchers. It had been recognized that high magnetic field affected the IMC layer growth by changing the atomic diffusion behavior in the solid Al/Mg and Al/Ni diffusion couples.3,4 Suppression of natural convection and induction of thermoelectromagnetic convection by high magnetic field had a nonlinear influence on the IMC layer thickness in Al/Cu couples.5,6 Recently, the interdiffusion behaviors in high magnetic field at liquid Bi/solid Bi0.4Sb0.6 interface indicated that the interfacial migration had been decreased by magnetic field.7 Although many studies have been carried out on the effect of magnetic field on interfacial IMC layer, so far the influence mechanism has not yet been understood clearly for the solid/solid or liquid/solid couples. As a lot of information about the growth of IMC layer between Sn-based alloy and Cu substrate can be used to understand the influence a)

Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2010.0055 J. Mater. Res., Vol. 25, No. 2, Feb 2010

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of magnetic field, the Sn-based alloy/Cu system has been the focus in our work. Also, our previous work8 indicated that the directions of high magnetic field also affected on the Cu6Sn5 IMC layer kinetics in solid Sn3Ag0.5Cu/Cu couples. The recent work on the morphologies of (Cu, Ni)6Sn5 layer at Sn0.3Ni/Cu interface indicated that high magnetic field changed the morphology of IMC layer by decreasing the content of Ni solute.9 However, whether magnetic field can affect the solute distribution at the in