Growth kinetics of Cu6Sn5 intermetallic compound at liquid-solid interfaces in Cu/Sn/Cu interconnects under...

Area of Science:

• Materials Science
• Metallurgy
• Surface Science

Background:

• Intermetallic compounds (IMCs) form at the interface between copper (Cu) and tin (Sn) during soldering processes.
• Understanding IMC growth is crucial for the reliability of electronic interconnects.
• Previous studies often focused on isothermal conditions, neglecting temperature gradients.

Purpose of the Study:

• To investigate the asymmetrical growth behavior of IMCs at liquid-solid interfaces in Cu/Sn/Cu interconnects under reflow conditions.
• To elucidate the influence of temperature gradients on IMC formation kinetics.
• To establish a growth model explaining the observed asymmetrical growth.

Main Methods:

• Experimental investigation of Cu/Sn/Cu interconnects reflowed at 250°C and 280°C on a hot plate.
• Analysis of interfacial IMC growth using microscopy and potentially other characterization techniques (implied).
• Development of a growth model incorporating thermomigration effects.

Main Results:

• Interfacial IMCs exhibited asymmetrical growth during reflow, unlike symmetrical growth during isothermal aging.
• Cu6Sn5 IMC growth was enhanced at the cold end, while Cu3Sn IMC growth was hindered at the hot end.
• Temperature gradients induced Cu atom migration from hot to cold ends, affecting atomic flux and reaction rates.

Conclusions:

• Temperature gradients significantly alter IMC growth mechanisms in Cu/Sn/Cu interconnects during reflow.
• The growth is controlled by a combination of reaction, thermomigration, and diffusion processes depending on the location (hot/cold end).
• Calculated molar heat of transport and thermomigration driving force provide quantitative insights into Cu atom behavior in molten Sn.