Poole frenkel currents and 1/f noise characteristics of high voltage MLCCs

摘要

DC leakage currents of MLCC (Multi Layerd Ceramc Capacitor)s show the typical Poole Frenkel relationship between the normalized current log (I/V) and the normalized voltage V within the specified voltage across the device without any local breakdown characteristics, giving the PF constants and the barrier heights of the insulating BaTiO3 layers. The typical 1/f noise characteristics are also observed, and the normalized noise amplitudes are obtained as the function of the MLCC series resistance, noise amplitudes of which are found more than 60 dB larger than those of the metal resistors. Both the leakage current and 1/f noise amplitudes give time saving reliability information much faster than those of the conventional MTTF method. The emerging needs of the ecological vehicles or the two cycle motor inverter systems accelerate the development of the high voltage MLCCs sharing a large part of capacitor applications. Up to 80 % of the total capacitors are made now by the MLCC. The MTTF method is usually applied as the standard conventional reliability test for these capacitors. Both the leakage current and 1/f noise amplitudes give time saving reliability information much faster than those of the conventional MTTF method. The leakage current in MLCC can be explained by the Poole-Frenkel tunneling effect. The normalized current (I/V) is linearly dependent on SQRT(V), noise levels are 60 to 80 dB larger than those of the conventional carbon resistors, with typical 1/f characteristics, dependent on the lots and independent of the biasing voltage.