Thermal Cycling, Mechanical Degradation, and the Effective Figure of Merit of a Thermoelectric Module

• Published in: Journal of electronic materials Vol. 42; no. 3; pp. 372 - 381
• Main Authors: Barako, M. T., Park, W., Marconnet, A. M., Asheghi, M., Goodson, K. E.
• Format: Journal Article
• Language: English
• Published: Boston Springer US 01.03.2013; Springer; Springer Nature B.V
• Subjects: Applied sciences; Characterization and Evaluation of Materials; Chemistry and Materials Science; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Conductivity phenomena in semiconductors and insulators; Electronic transport in condensed matter; Electronics; Electronics and Microelectronics; Exact sciences and technology; Heat conductivity; Instrumentation; Materials; Materials Science; Mechanical properties; Optical and Electronic Materials; Physics; Scanning electron microscopy; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Solid State Physics; Thermal cycling; Thermoelectric and thermomagnetic effects; Thermoelectric, pyroelectric devices, etc; Thermography; Harman method; Thermoelectric module; figure of merit; infrared microscopy; thermal cycling; Scanning electron microscopy; Electrical conductivity; Thermal cycle; Seebeck effect; Steady state; Thermoelectric properties; Thermoelectric device; Thermoelectric power; Thermal conductivity; Defect; Figure of merit; Thermomechanical stress; Thermal degradation
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-012-2366-1

Thermoelectric modules experience performance reduction and mechanical failure due to thermomechanical stresses induced by thermal cycling. The present study subjects a thermoelectric module to thermal cycling and evaluates the evolution of its thermoelectric performance through measurements of the thermoelectric figure of merit, ZT , and its individual components. The Seebeck coefficient and thermal conductivity are measured using steady-state infrared microscopy, and the electrical conductivity and ZT are evaluated using the Harman technique. These properties are tracked over many cycles until device failure after 45,000 thermal cycles. The mechanical failure of the TE module is analyzed using high-resolution infrared microscopy and scanning electron microscopy. A reduction in electrical conductivity is the primary mechanism of performance reduction and is likely associated with defects observed during cycling. The effective figure of merit is reduced by 20% through 40,000 cycles and drops by 97% at 45,000 cycles. These results quantify the effect of thermal cycling on a commercial TE module and provide insight into the packaging of a complete TE module for reliable operation.