Effect of the ENEPIG Process on the Bonding Strength of BiTe-based Thermoelectric Elements

To improve the mechanical performance of BiTe-based thermoelectric modules, this study applies anti-diffusion layers that inhibit the generation of metal intercompounds and an electroless nickel/electrode palladium/mission gold (ENEPIG) plating layers to ensure a stable bonding interface. If a plated layer is formed only on BiTe-based thermoelectric, the diffusion of Cu in electrode substrates produces an intermetallic compound. Therefore, the ENEPIG process was applied on the Cu electrode substrate. The bonding strength highly increased from approximately 10.4 to 16.4 MPa when ENEPIG plating was conducted to the BiTe-based thermoelectric element. When ENEPIG plating was performed to both the BiTe-based thermoelectric element and the Cu electrode substrate, the bonding strength showed the highest value of approximately 17.6 MPa, suggesting that the ENEPIG process is ef-fective in ensuring a highly reliable bonding interface of the BiTe-based thermoelectric module.