ECN publication
Measurement of strains in MWT modules during manufacture
Published by: Publication date:
ECN Solar Energy 5-2-2013
ECN report number: Document type:
ECN-M--12-026 Conference Paper
Number of pages: Full text:
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Presented at: Silicon PV Conference, Leuven, , 3-5 april 2012.

In this paper a method of measuring the residual strains in a foil-based MWT module is introduced. These strains are a result of differences in thermal expansion coefficients between the different components in the module. The method involves the design and manufacture of a test module allowing the different components to be visualised and the development of a camera system and software for strain measurement and analysis. Strains were measured in the glass, cells and back-sheet foil for a module laminated at 150°C and subsequently cooled to room temperature. The results show that strain is dominated by the glass sheet and that strain is uniform in the glass and cells, but complex in the foil. Strain in the foil and cell is relatively small. Parallel to this, a study was made of the relationship between the position of a conductive adhesive contact in the module and its shape. Analysis of the shape showed that a contact with concave sides was the most stable, whereas contacts with a convex shape result in a weaker interface with the cell and foil. Combining the two techniques allows analysis of the module design, in particular of the interconnections. The results can be used to adjust, for example, the foil specification and the conductive adhesive print size. This will result in an improved module reliability and lifetime.

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