Interfacial Reactions between Sn-Based Solders and n-Type Bi₂(Te,Se)₃ Thermoelectric Material.

Area of Science:

• Materials Science
• Solid-State Chemistry
• Thermoelectric Materials

Background:

• Bismuth telluride (Bi2Te3) based materials are crucial for thermoelectric applications.
• Understanding interfacial reactions between thermoelectric materials and solders is vital for device reliability and performance.
• Previous studies focused on p-type (Bi,Sb)2Te3, necessitating research on n-type Bi2(Te,Se)3.

Purpose of the Study:

• To investigate the interfacial reactions between n-type Bi2(Te,Se)3 and Sn or Sn-Ag-Cu solders.
• To elucidate the reaction mechanisms and kinetics governing intermetallic compound formation.
• To compare the reaction behavior of n-type Bi2(Te,Se)3 with p-type (Bi,Sb)2Te3.

Main Methods:

• Experimental investigation of interfacial reactions under liquid and solid-state conditions.
• Microstructural analysis of reaction products and interfacial layers.
• Kinetic analysis of intermetallic compound growth using diffusion-controlled models.

Main Results:

• Liquid-state reactions formed SnTe and BiTe phases, with Bi-rich particles in SnTe. SnTe growth followed parabolic kinetics.
• Solid-state reactions showed similar microstructures, with SnTe as the primary product and minimal BiTe growth.
• Se in Bi2(Te,Se)3 significantly suppressed SnTe growth compared to (Bi,Sb)2Te3. Cu diffused into the SnTe phase in Sn-Ag-Cu solder reactions.

Conclusions:

• The interfacial reaction between n-type Bi2(Te,Se)3 and Sn-based solders is diffusion-controlled.
• Selenium plays a critical role in suppressing interfacial reaction rates, enhancing material stability.
• Understanding these reactions is key for optimizing the packaging and long-term performance of thermoelectric devices.