Abstract:

Currently, the world is at the intersection of the energy and computer revolutions. The electronic information industry, driven by the fields of 5G communication, smartphones, and new energy vehicles, is booming and has become an important pillar of the economic market. Multilayer ceramic capacitors (MLCC), which are passive electronic components with the highest market share, are one of the key products that require breakthroughs in key technologies in the basic electronic component industry, with wide applications in automotive electronics, power grid frequency modulation, aerospace, and other fields. With the trend of miniaturization and thin lamination, the thickness of the dielectric layer in the MLCC is decreasing continuously, whereas the electric field on the single dielectric layer is increasing significantly when the MLCC is applied under the same voltage, particularly for the ultrathin-layered MLCC served under medium/high voltage. Consequently, the reliability of MLCC has become a key product quality indicator. In this study, the deterioration mechanism of ultrathin-layer MLCC is systematically studied via accelerated aging tests, high-temperature impedance spectroscopy, and leakage current tests. During the accelerated aging test, the ceramic dielectrics degrades under the applied strict electric field and temperature, and the oxygen vacancies gradually migrate in grains and transgranularly, finally accumulating near the cathode, as observed by transmission electron microscopy. Consequently, a semiconducting layer with poor insulation performance near the cathode is formed, and the barrier height at the interface is reduced. Based on the results of the high-temperature impedance spectroscopy and leakage current test, the activation energy at the grain boundary and dielectric-electrode interface decreases, and the leakage current density increases significantly for the aged MLCC. The formation of an oxygen-vacancy-enriched semiconducting layer is a great threat to the reliability of MLCC, particularly under the trend of developing increasingly thinner dielectric layers. Therefore, inhibiting the migration and enrichment of oxygen vacancies is a top priority for ensuring the reliability of MLCC. To improve the reliability of ultrathin-layered MLCC, the oxygen vacancy concentration in ceramic dielectrics should be reduced, the activation energy required for its migration should be increased, and the Schottky barrier at the interface should be improved. All these results provide a powerful guide for the design of ultrathin-layered MLCC dielectric materials, which is expected to promote the upgrade iteration of high-end MLCC.

Key words: Barium titanate, Multilayer ceramic capacitor, Reliability, Accelerated aging, Oxygen vacancy