Terahertz Inspection of the Joining Quality of Industrial Silicon Carbide Ceramics

We present in our contribution first investigations towards quality inspection of joining interfaces of silicon carbide (SiC) and silicon nitride (SiN) ceramics for industrial applications. In time-domain spectroscopy (TDS) terahertz transmission measurements, we find significant transmission through relevant SiC and SiN samples, mainly in correlation with the sample's resistivities. Differences in resistivity at the interfaces of joined ceramics could therefore be used for the evaluation of the quality of these joinings. Images of an examplary joined SiC component with an artificial inner structure were recorded with an allelectronic, frequency-modulated continuous wave (FMCW) terahertz radar at 100 GHz in a reflection geometry. The images clearly reveal the inner structure of the component at the depth of the joining interface. Based on these first findings, further studies on quality inspection of SiC joinings are being carried out.