Phase field simulations of intermetallic compound growth during soldering reactions

Abstract

Phase field simulations of the microstructural evolution of the intermetallic compound (IMC) layer formed during isothermal soldering reactions between Sn-Cu solder alloys and a Cu substrate are presented. The simulation accounts for the fast grain boundary (GB) diffusion in the IMC layer, the concurrent IMC grain coarsening along with the IMC layer growth, and the dissolution of Cu from the substrate and IMC layer. The simulation results support the previous suggestions that the growth kinetics of the IMC layer during soldering is predominantly governed by the fast GB diffusion and the concurrent coarsening rate of the IMC grains. The IMC grain coarsening is initiated by a competitive growth of the IMC grains at the solder/IMC interface. It is also shown that the dissolution of Cu into an unsaturated solder reduces the coarsening rate of the IMC grains, consequently decreasing the temporal growth exponent of the IMC layer.

Formation and Growth of Intermetallic Compound Cu6Sn5 at Early Stages in Lead-Free Soldering

“…Contrary to the early stages of morphological evolution, one can find that g grain growth in the late stages for case 1 and case 2 are similar to the results from previous works. 10,18,25 In the low-D GB scenario (case 2), the Cu substrate is not readily dissolved to form Cu 6 Sn 5 grains, so that the thickness of the IMC phase shows a lower rate of increase compared with case 1, which is in good agreement with previous work. 25 At the early stage (t < 0.1 s) during lead-free soldering in Fig.…”

“…10,18,25 In the low-D GB scenario (case 2), the Cu substrate is not readily dissolved to form Cu 6 Sn 5 grains, so that the thickness of the IMC phase shows a lower rate of increase compared with case 1, which is in good agreement with previous work. 25 At the early stage (t < 0.1 s) during lead-free soldering in Fig. 4, the Cu substrate thickness remains unchanged, the thickness of the IMC increases gradually, and the number of IMC grains is not changed.…”

“…Model parameters for the multiphase field equation can be obtained from a stationary solution of the phase-field equation along a planar interface, which results in two relationships between model parameters and material parameters associated with the definition of the interface energy as a function of gradient energy coefficient and phase field with a referred interface width 25,28 :…”

“…IMC growth has been modeled previously [24][25][26] by using phasefield approaches. 27,28 These mathematical models have proved to be a very useful tool to investigate the microstructural evolution of IMCs as a function of factors such as solid/liquid interfacial energies, grain boundary energies, relative mass transport enhancement by grain boundaries, and so forth.…”

“…27,28 These mathematical models have proved to be a very useful tool to investigate the microstructural evolution of IMCs as a function of factors such as solid/liquid interfacial energies, grain boundary energies, relative mass transport enhancement by grain boundaries, and so forth. [24][25][26] So far, these simulation efforts have focused on the evolution of IMC layers at late stages.…”