5 September 2014 IR-imaging based system for detecting the defects of conductive materials
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Uniformity of conductive materials is an important property which is measured during manufacturing and in finished products, especially in electronics applications such as organic solar cells. Differences in uniformity are often very small, invisible or below the surface of the sample. Therefore, they are not always detectable even by high-resolution imaging systems. Respectively, electrical conductivity measurements are limited to those mainly between the measuring probes. Uniformity difference measurements are time-consuming in the case of a large area characterization. To bypass the described limitations, a simple heating and IR-imaging based system was designed and demonstrated with conductive materials. Samples with different defects were used to investigate the correlation of conductance and defect positioning. By making punched holes in the samples, it was possible to demonstrate how the local resistances of thin films have functions to each other and how this may be observed on an IR-figure. Thermographs of punched thin films confirm that those areas where the holes prevented the current flow have lower heat emissions. Therefore, it can also be concluded that, generally, the temperature is highest at the areas where current density is highest. When comparing the defects of bent samples to these punctured ones, the correlations of resistance and breakage areas were comparable. The applied system is capable of localizing small defects in large-area samples using a single IR-image. This is a significant advantage from the manufacturing process measurement point of view.
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Kimmo Leppänen, Kimmo Leppänen, Juha Saarela, Juha Saarela, Tapio Fabritius, Tapio Fabritius, "IR-imaging based system for detecting the defects of conductive materials", Proc. SPIE 9205, Reflection, Scattering, and Diffraction from Surfaces IV, 92050M (5 September 2014); doi: 10.1117/12.2060834; https://doi.org/10.1117/12.2060834

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