Thermography: quality control for module manufacturing

It is beneficial to check the quality of the strings of cells prior to the final lamination process to avoid the rejection of a complete laminate in case of a defective string. Defective cells or defective connections can be detected in a fairly simple way prior to the lamination process by thermography. Within a few seconds after applying a reverse current in the order of the short circuit current of the cells a clear IR-image can be observed. The image may be obscured by local variations in the emission coefficient for IR radiation. This complication however is successfully tackled by covering the string with a simple plastic foil. The foil takes over the temperature distribution of the underlying string and emits the radiation with a uniform emission coefficient.