Home – Home – Jornals – Chemistry for Sustainable Development 2019 number 5

One of the main requirements for tantalum oxide semiconductor capacitors is the reduction of the equivalent series resistance (EPS), the value of which is directly related to the electrical conductivity of the semiconductor manganese dioxide layer formed on the surface of the tantalum electrode. Analysis of the current state of the production of electrolytic capacitors in Russia showed that the industry survives a steady trend towards an increase in switching frequencies from 10 to 100 kHz and higher, necessitating a reduction in the EPS of the finished capacitor. At the same time, manufactured products do not have the necessary characteristics for operation at higher frequencies. Existing technology solutions do not provide the production of high-quality capacitors, since they are multistage, energy-intensive and require continuous improvement. This paper deals with the search for ways to improve the electrical characteristics of a manganese dioxide cathode coating on tantalum oxide semiconductor capacitors. A theoretical analysis of the literature was conducted in order to determine the probable causes of the increased equivalent series resistance of a capacitor. The properties of factory-made tantalum oxide semiconductor capacitors were investigated by means of X-ray phase and photomicroscopic analysis; their electrical parameters were determined. It was shown that an increase in the equivalent series resistance of capacitors is due to the presence of an impurity of high-resistance manganese oxide (III) in the composition of the cathode coating based on manganese dioxide. It was established that manganese oxide (III) contaminates the impregnating solution of manganese nitrate, from which the cathode coating on tantalum bulk-porous anodes is obtained by thermal decomposition. To reduce the EPS of the finished capacitor, a method is developed for removing manganese oxide (III) from the semiconductor coating by cleaning the precursor, manganese nitrate, and modifying the surface of the cathode coating with oxidizing agents. The proposed method can be recommended for practical implementation in the production of tantalum oxide semiconductor capacitors, which will improve the electrical characteristics by reducing the equivalent series resistance of finished products.