Thermal and Mechanical Fatigue Including Vibration: Task Group 2

Task Group 2 is focused on thermal and mechanical fatigue.

Failures of cell interconnects and solder bonds are a key cause of long-term failure of PV modules. The primary stresses affecting the failure rates are thermal and mechanical. This task group studies how to induce and quantify these failures.

Progress Update

There is a consensus that 200 thermal cycles do not adequately stress a module, so discussion has focused on how to increase the amount of stress without extending the test for a prolonged time. Finite element modeling (FEM) has quantified the number of thermal cycles in the chamber needed to simulate a lifetime in the field. FEM analyses on the rate of solder fatigue damage has revealed that the number of thermal cycles (required for an equivalent exposure to an envisioned climate) would be significantly reduced by the increase in the maximum cycle temperature. Moreover, since the acceleration factor between the thermal cycling test with the increased maximum temperature and outdoor service was (nearly) identical even when some variables (such as laminate layer thicknesses and thermomechanical properties of materials) were changed, it is expected that this test protocol can apply the adequate thermomechanical stress to PV modules with various designs.

Standards Activities

Based on the above FEM studies, a New Work Item Proposal and Committee Draft on IEC 62892 ED. 1 "Extended Thermal Cycling of PV Modules - Test Procedure" was reviewed by International Electrotechnical Commission (IEC) TC82/WG2. It is now approved as the Final Draft International Standard as of February 2019. This draft provides options for reducing the time for the thermal cycling test by increasing the maximum temperature and/or increasing the sample size being tested.

Related Resources

IEC 62892 ED1 “Extended Thermal Cycling of PV Modules - Test Procedure”

Climate Specific Thermomechanical Fatigue of Flat Plate Photovoltaic Module Solder Joints (2016)
Authors: Bosco, N., Silverman, T. J., and Kurtz, S.
Journal: Microelectronics Reliability

The Influence of PV Module Materials and Design on Solder Joint Thermal Fatigue Durability (2016)
Authors: Bosco, N., Silverman, T. J., and Kurtz, S.
Journal: IEEE Journal of Photovoltaics

Causes of Degradation Identified by the Extended Thermal Cycling Test on Commercially Available Crystalline Silicon Photovoltaic Modules (2017)
Authors: Kawai, S., Tanahashi, T., Fukumoto, Y., Tamai, F., Masuda, A., and Kondo, M.
Journal: IEEE Journal of Photovoltaics

Task Leaders

Nick Bosco — National Renewable Energy Laboratory, representing the Americas
Tadanori Tanahashi — National Institute of Advanced Industrial Science, representing Japan
Simon Xiao — Trina Solar, representing China

Other leaders are welcome.