Study of the Reactive Diffusion in the Presence of Dissolution of Copper in the Solder Melts

Abstract

In this work we give heed especially to the dominating process which is the solid metal A dissolving in the melt B. During the dissolving, the melt B saturates with the metal A and the process is influenced by convections which are characteristic for the given experimental configuration. A theoretical description of the kinetics of the solid phase dissolving in melt will be presented for the case of planar and cylindrical dissolving. The aim is to derive a relation for the interface boundary (t) movement in dependence on time and a time course of growth of the element A concentration in the melt B. There are problems with an accurate determination of the interface boundary movement after certain heating times of specimens, when it is observed experimentally, since intermetallic phases create in the original A metal at both the diffusion and cooling and some phases segregate at the solidifying melt cooling. The rate constant is a fundamental parameter characterizing the dissolving rate at a certain configuration. We present a theoretical description of dissolving of a long metallic cylinder submerged into a melt column and relations for the rate constant determination from the time of the whole metallic cylinder dissolution are derived. In our experiments were performed in which Cu was dissolving in the Sn melt for a Cu cylinder (wire) diameters 0.8÷2.5 mm and the rate constant K (T = 350°C) was determined. Relationships between the solid phase dissolving rate, i.e. the solid phase interface boundary movement (t) in the melt and rates of growth of intermetallic phases in the metal A will be observed. This procedure enables to create surface and subsurface layers of regulated thickness in metallic materials by means of reactive diffusion.

Full text

Study of the Reactive Diffusion in the Presence of Dissolution of Copper
in the Solder Melts
Jaromír Drápala1,a, Petr Kubíček2, b
1Vysoká škola báňská – Technical University of Ostrava; Faculty of Metallurgy and Materials
Engineering; 15, Av. 17. listopadu, 708 33 Ostrava – Poruba, Czech Republic
2Na Čtvrti 14, 700 30 Ostrava-Hrabůvka, Czech Republic
aJaromir.Drapala@vsb.cz, bmarcela.kubickova@seznam.cz
Keywords: Reactive diffusion, dissolution, copper, tin, indium, solder, melt, rate constant, interface
boundary movement, thermodynamic equilibrium.
Abstract. In this work we give heed especially to the dominating process which is the solid metal A
dissolving in the melt B. During the dissolving, the melt B saturates with the metal A and the
process is influenced by convections which are characteristic for the given experimental
configuration. A theoretical description of the kinetics of the solid phase dissolving in melt will be
presented for the case of planar and cylindrical dissolving. The aim is to derive a relation for the
interface boundary

(t) movement in dependence on time and a time course of growth of the
element A concentration in the melt B. There are problems with an accurate determination of the
interface boundary movement after certain heating times of specimens, when it is observed
experimentally, since intermetallic phases create in the original A metal at both the diffusion and
cooling and some phases segregate at the solidifying melt cooling. The rate constant is a
fundamental parameter characterizing the dissolving rate at a certain configuration. We present a
theoretical description of dissolving of a long metallic cylinder submerged into a melt column and
relations for the rate constant determination from the time of the whole metallic cylinder dissolution
are derived. In our experiments were performed in which Cu was dissolving in the Sn melt for a Cu
cylinder (wire) diameters 0.8÷2.5 mm and the rate constant K (T = 350°C) was determined.
Relationships between the solid phase dissolving rate, i.e. the solid phase interface boundary
movement

(t) in the melt and rates of growth of intermetallic phases in the metal A will be
observed. This procedure enables to create surface and subsurface layers of regulated thickness in
metallic materials by means of reactive diffusion.
Introduction
Reactive diffusion is accompanied by phase changes in materials. It can be observed in cases when
the atoms of matrix and diffusant are mutually limitedly miscible or they can form compounds with
each other. Solid solutions of the basic components A and B form in the diffusion layer and areas of
other phases of different widths may be found among them in conformity with the corresponding
phase diagram. There is always a concentration jump on the interface boundary if the binary or
ternary system does not show a total solubility in the solid state. The result of reactive diffusion is
coexistence of several successive layers of solid solutions or chemical compounds (intermetallic
phases). The width of the areas, i.e. the thickness of individual phases, will depend on the values of
interdiffusion coefficients of elements in each of the present phases. Reactive diffusion also occurs
at soldering of electronic components on printed circuit cards when reactions between tin and copper
proceed and the thin function layer (Cu11Sn9) creates. Reactive diffusion is also applied when
producing function gradient materials, etc.
Defect and Diffusion Forum Online: 2010-04-13
ISSN: 1662-9507, Vols. 297-301, pp 8-14
doi:10.4028/www.scientific.net/DDF.297-301.8
© 2010 Trans Tech Publications Ltd, All Rights Reserved
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