Effect of NiMo diffusion barrier plating preparation on microstructure and properties of Bi2Te3/Cu joints

Abstract

Bismuth telluride (Bi2Te3) thermoelectric devices play a significant role in recovering low-grade waste heat. While for Bi2Te3/Cu joints, excessive interfacial reaction and diffusion usually happens, which greatly degrades their properties. In this work, the novel NiMo diffusion barrier plating was prepared on Bi2Te2.7Se0.3 (n-BST) surface prior to the soldering process. The joint interfacial microstructure, shear strength, contact resistance and thermal stability were systematically investigated. The maximum shear strength increased from 7 MPa to 12 MPa with the joint contact resistance decreasing from 11.86 μΩ⋅cm2 to 3.27 μΩ⋅cm2 after NiMo plating preparation. These n-BST/Cu joints were then annealed for different durations to investigate the joint thermal stability. After annealing at 110 °C for 250 h, a thin BiTe + NiTe2 reaction layer formed instead of the initial SnTe reaction layer. The joint shear strength maintained 9 MPa (less than 2 MPa without NiMo plating) and the joint contact resistance was only 12.39 μΩ⋅cm2 (249.89 μΩ⋅cm2 without NiMo plating). This work indicates that NiMo plating is an effective elemental diffusion barrier for n-BST/Cu joints.