Activation Energy for End-of-Life Solder Bond Degradation: Thermal Cycling of Field-Aged PV Modules

Journal Article · Mon Oct 05 00:00:00 UTC 2020 · IEEE Journal of Photovoltaics

DOI: https://doi.org/10.1109/jphotov.2020.3025726 · OSTI ID:1770900

Gopalakrishna, Hamsini  ^[1]; Sinha, Archana  ^[1]; Carpenter, Joe  ^[1]; Niverty, Sridhar ^[1]; Chawla, Nikhilesh ^[1]; Jordan, Dirk  ^[2]; Tamizhmani, Govindasamy ^[1]

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1. Arizona State Univ., Mesa, AZ (United States)
2. National Renewable Energy Lab. (NREL), Golden, CO (United States)

The longevity of solar photovoltaic modules depends on the durability and reliability of their components, one of which is the solder bonds in interconnect ribbons. The solder joints experience stresses from thermal cycling and constant elevated temperatures (40 °C-70 °C) in regular field operation leading to thermo-mechanical fatigue and intermetallic compound formation. To study the end-of-life wear-out mechanisms and to obtain activation energy of solder bond degradation, here two field-aged modules from Arizona-a 21-year-old Solarex MSX60 module (with Sn62Pb36Ag2 at the solder joints) and an 18-year-old Siemens M55 module (with Sn60Pb40 at the solder joints)-underwent 800 and 400 modified thermal cycles, respectively. Using three heating blankets, each module had three temperature zones maintained at 85, 95, and 105 °C during the 15-min hot dwell time of the thermal cycle. Cell-level series resistance data obtained from three temperature zones enabled the calculation of activation energy for solder bond degradation for the MSX60 and the M55 modules to be 0.12 eV and 0.35 eV, respectively. From each temperature zone in both modules, busbar-solder samples were obtained, imaged through SEM, and analyzed with energy-dispersive X-ray spectroscopy. In the MSX60 module with traces of Ag in the solder material, phase segregation and growth were primarily observed at high temperatures. For M55 modules without Ag in the solder material, major phase segregation was observed in all temperature zones. The IMC thickness for both modules increased with increasing module temperature. The beneficial effect of Ag in solder material on mitigating solder bond degradation is presented.

• Research Organization: National Renewable Energy Laboratory (NREL), Golden, CO (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office
• Grant/Contract Number: AC36-08GO28308; EE0007138
• OSTI ID: 1770900
• Report Number(s): NREL/JA--5K00-79404; MainId:33630; UUID:694ad14f-0a07-491f-9238-6143c5e16655; MainAdminID:19930
• Journal Information: IEEE Journal of Photovoltaics, Journal Name: IEEE Journal of Photovoltaics Journal Issue: 6 Vol. 10; ISSN 2156-3381
• Publisher: IEEECopyright Statement
• Country of Publication: United States
• Language: English