Thermomechanical Fatigue Resistance of Low Temperature Solder for Multiwire Interconnects in Photovoltaic Modules

Laura Spinella, Nick Bosco

Research output: Contribution to journalArticlepeer-review

11 Scopus Citations

Abstract

Novel interconnect technologies leveraging low melting temperature solders, such as multiwire interconnects, are being deployed in photovoltaic (PV) modules for improved reliability through interconnect redundancy and lower thermal loads during interconnection and lamination. However, the equivalency of standardized accelerated testing to field conditions has not yet been established for these emerging technologies. In this study, the thermomechanical fatigue resistance of low temperature solder alloys is investigated and compared to that of conventional SnPb to assess the acceleration behavior of these alloys. While InSn is shown to have sufficient thermomechanical fatigue resistance on the order of that of SnPb, these results indicate Sn–Bi alloys may have poor thermomechanical fatigue resistance at field conditions. The results also show that Sn–Bi alloys have thermal cycling acceleration factors of less than one. This indicates that the standardized accelerated thermal cycling test, such as that in IEC 61215, will produce misleading results for Sn–Bi alloys and that unique testing is required for this PV module architecture. Though accelerated thermal cycling may be a meaningful qualification test for SnPb solder joints, these results suggest that mechanical loading may be a more appropriate test for Sn–Bi multiwire interconnects. This is due to the distinct processing and geometry of multiwire interconnects which may allow for mechanical, rather than strictly metallurgical interconnections.

Original languageAmerican English
Article numberArticle No. 111054
Number of pages6
JournalSolar Energy Materials and Solar Cells
Volume225
DOIs
StatePublished - 15 Jun 2021

Bibliographical note

Publisher Copyright:
© 2021

NREL Publication Number

  • NREL/JA-5K00-78350

Keywords

  • Accelerated testing
  • Bismuth
  • Durability
  • Indium
  • Low temperature solder
  • Multiwire interconnects

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