Molecular Dynamics Simulation of the Cu₃Sn/Cu Interfacial Diffusion Mechanism under Electrothermal Coupling

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Materials Science

Background:

• Solder joints in high-power electronics face reliability issues due to electromigration under high currents.
• Understanding diffusion mechanisms at interfaces is crucial for improving device longevity.

Purpose of the Study:

• To investigate the diffusion mechanism of the Copper-Tin (Cu3Sn)/Copper (Cu) interface under electrothermal coupling.
• To elucidate the role of electric fields and vacancies in accelerating interface diffusion.

Main Methods:

• Utilizing molecular dynamics simulations to model the behavior of the Cu3Sn/Cu interface.
• Analyzing the effects of electric field intensity and temperature on diffusion activation energy and atomic displacement.

Main Results:

• Diffusion activation energy decreases with increasing electric field intensity, accelerating Cu3Sn/Cu interface diffusion.
• Vacancy response, indicated by abrupt changes in vacancy-time curves, lags behind atomic displacement (mean square displacement), suggesting electric field-driven vacancy dynamics.
• Increased vacancy concentration and accelerated vacancy movement were observed due to atoms overcoming interatomic forces in the electric field.

Conclusions:

• A novel vacancy-responsive diffusion mechanism for the Cu3Sn/Cu interface under electrothermal coupling is proposed.
• Electric fields directly influence vacancy behavior, leading to enhanced diffusion and potential degradation of solder joint reliability.
• The findings provide insights for designing more robust electronic devices resistant to electromigration failure.