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ISSN Online: 2377-424X

ISBN CD: 1-56700-226-9

ISBN Online: 1-56700-225-0

International Heat Transfer Conference 13
August, 13-18, 2006, Sydney, Australia

MASS TRANSPORT DURING DIFFUSION SOLDERING OR BRAZING AT CONSTANT TEMPERATURE

Get access (open in a dialog) DOI: 10.1615/IHTC13.p10.110
12 pages

Resumo

The back-diffusion phenomenon is employed to develop the model for a solute redistribution. The model is applied for describing the formation of inter-metallic phases or compounds within a multilayers interconnection produced by diffusion soldering or brazing. The solidification of a given inter-metallic phase or compound sub-layer is referred to a proper peritectic reaction as it results from a phase diagram of stable equilibrium. A formation of Ni/Al/Ni and Fe/Zn/Fe interconnections is analysed. Al-solute or Zn-solute redistribution and thickness of sub-layers are measured in the soldered Ni/Al/Ni and Fe/Zn/Fe interconnections, respectively. The comparison of the profile of solute redistribution predicted by the model with the profile of solute redistribution measured across an interconnection is performed. The effect of the back-diffusion onto thickening of sub-layers and solute redistribution in the Ni/Al/Ni interconnection is discussed. The sequence of appearing phases or compounds during diffusion soldering is observed by arresting solidification or first solid/solid transformation. A competition between meta-stable phase growth and stable phase growth during first period of solidification is considered. The birth of the phase, second in sequence (for the Ni/Al/Ni joint) or birth of the phase, third in sequence (for the Fe/Zn/Fe joint) is revealed. The zero number degrees of freedom for both systems Ni/Al/Ni and Fe/Zn/Fe is envisaged from the view point of the Gibbs phase rule. A solidification path for diffusion soldering is defined. The first solid / solid transformation is described as a kind of chemical reaction and shown experimentally as consumption of the second phase in sequence (for the Ni/Al/Ni joint) or third phase in sequence (for the Fe/Zn/Fe joint) by a so-called dominant phase. The revealed consumption named as a "mantis" phenomenon is an independent behaviour of the system and occurs just after solidification. The formulated set of equations is referred to the concept of undercooled liquid, dx, formed due to dissolution of the substrate by the liquid solution of the filler metal. The heat transfer for the period of zinc freezing which precedes the processes of dissolution/solidification is also considered.