Effect of viscoelasticity of ethylene vinyl acetate encapsulants on photovoltaic module solder joint degradation due to thermomechanical fatigue

• Published in: Japanese Journal of Applied Physics Vol. 57; no. 8S3; pp. 8 - 12
• Main Authors: Zhu, Jiang, Owen-Bellini, Michael, Montiel-Chicharro, Daniel, Betts, Thomas R., Gottschalg, Ralph
• Format: Journal Article
• Language: English
• Published: Tokyo The Japan Society of Applied Physics 01.08.2018; Japanese Journal of Applied Physics
• Subjects: Computer simulation; Degradation; Encapsulation; Equivalence; Ethylene vinyl acetates; Finite element method; Materials fatigue; Modules; Photovoltaic cells; Power loss; Resistance factors; Solar cells; Soldered joints; Stresses; Two dimensional analysis; Two dimensional models; Viscoelasticity
• ISSN: 0021-4922; 1347-4065
• DOI: 10.7567/JJAP.57.08RG03

The solder joint degradation due to thermomechanical fatigue is investigated in this paper for photovoltaic (PV) mini-modules with ethylene vinyl acetate (EVA) of different viscoelastic properties. The mini-modules were laminated at different curing temperatures in order to obtain EVA encapsulation with different viscoelastic properties. The influence of viscoelasticity of EVA on the thermomechanical fatigue generated on solder joint is analyzed based on a two-dimensional (2D) finite-element model. Based on simulation of thermomechanical stresses accumulation, mini-modules with EVA cured at lower temperatures accumulated approximately 40% more stresses during the thermal cycle testing than mini-modules with optimal cured EVA. The tested mini-modules with EVA cured at lower temperature showed greater power degradation than the optimal cured mini-modules. An apparent increase in equivalent series resistance is the primary factor the power loss. A good correlation between the accumulated thermomechanical fatigue and the increase in equivalent series resistance is demonstrated with the tested samples.