Development of a Simplistic Method to Simulate the Formation of Intermetallic Compounds in Diffusion Soldering Process

Abstract

A simplistic simulation technique has been developed for computing the individual intermetallic compound (IMC) thickness which is formed in substrate-solder (Cu-Sn) systems during the diffusion soldering process in high-temperature power electronic applications. The method requires the time-dependent temperature profile for the soldering process and the growth rate parameters (e.g. concentration gradient, diffusion coefficient, activation energy, etc.) for the development of IMC layers as input. The method is suitable for predicting the thickness of an intermetallic phase layer during the diffusion soldering process. As such, it can be used in high-temperature power electronic application's solder processing to enhance the reliability and lifetime of solder interconnections by allowing the control of the thickness of IMC layers. The method is demonstrated for IMC growth between pure copper as substrate and pure Sn as solder material. The growth behavior of the IMC layer is increased with increasing temperature over time according to the Arrhenius theory in the temperature range between 24°C to 260°C. To simulate the formation of IMC thickness in diffusion soldering interconnections, a simplistic way has been attempted using the popular commercial finite element simulation tool Comsol Multiphysics and scientific computing application 'Matlab'. By means of transient thermal input, the diffusion-controlled intermetallic phase formation is simulated here. Few assumptions are taken care of this simulation process, for example, no convection, no reaction, solid-solid diffusion, no the pressure effect on the computational domain.

Localized Induction Heating of Cu-Sn Layers for Rapid Solid-Liquid Interdiffusion Bonding Based on Miniaturized Coils

“…The SLID bonding (also known as Transient Liquid Phase Bonding) is a packaging technique based on intermetallic diffusion between two or more metals, with a hightemperature melting metal (such as Cu or Au) and a low-temperature melting metal (such as Sn or In) under the influence of temperature, time, and pressure. Intermetallic formation is driven by the atomic concentration gradient and can be described by the second Fick's law of diffusion [46]. It states that the diffusive flux goes from a high-concentration area to a low-concentration area proportional to the concentration gradient.…”

“…The diffusion process of unalloyed copper and tin will accelerate by exceeding the melting point of Sn (T M_Sn = 232 • C). The temperature range used in the literature is between 250 • C and 300 • C [14,15,19,20,46], resulting in intermetallic bonds of Cu 6 Sn 5 (η-phase) and Cu 3 Sn (ε-phase) during the bonding process. The η-phase is formed in the early heating stage.…”