Non-Destructive Measurement of EVA Cross-Linking


Project Motivation

The degree of EVA cross-linking that takes place during lamination can determine PV module lifetime. Fraunhofer CSE undertook a study of non-destructive measurement techniques for EVA cross-linking, ultimately producing and patenting a metrology method suitable for module manufacturing lines.

Stress Relaxation: A Novel Technique

The CSE team demonstrated that a mechanical measurement of elasticity (indentation) is predictive of the level of cross-linking. This non-destructive technique is now available for in-line quality control in manufacturing. The method replaces a solvent technique, which is destructive and has low throughput.

Benefits of Indentation Testing

Indentation testing is a reliable method to determine encapsulant cross-linking levels. Benefits include:

  • Non-destructive procedure
  • Can be carried out In-situ
  • Chemical-free
  • Rapid testing: seconds, not hours
  • Allows mapping across the module area

The X-Link Metrology System

In 2011, Fraunhofer CSE licensed its method to LayTec AG, a manufacturer of in-situ metrology systems for thin-film processes. In May 2012, LayTec announced its X Link in-line metrology system, the first commercial application of Fraunhofer CSE intellectual property.

The X Link was exhibited at SNEC’s 6th International Photovoltaic Power Generation Conference Exhibition in Shanghai, China, and at Intersolar North America 2012.


Cordula Schmid, Ph.D.
Associate Director, Photovoltaic Technologies
Office +1 (617) 714-6515