Ing. Martin Horák, Ph.D.

Wafer resistivity is one of the most important parameters in production of Power Semiconductor Devices (PSD). This parameter is mainly responsible for achieving required breakdown voltage and other electric parameters. Proposal article describes principles and details of newly designed resonant method and new equipment according patent [1] and compares it with commonly known 4point method. This new method is based on resonant measurement of capacity and following calculation. New method exhibits comparable accuracy with 4point method and brings additional advantages.

For effective use of conductive adhesives in a variety of conditions, it is necessary to know how strong the influence on the resistance of the adhesive joint has factors associated with these conditions. The experiments have been carried out with 6 types of conductive adhesives. the effect of curing, humidity, the influence of DC current, and modifying the adhesive with nanoparticles was tested. Theoretical analysis has been carried out using full factorial experiments and Taguchi orthogonal arrays.

A rapid method based on activation energy values for the lifetime assessment of PP films used as dielectrics for capacitors is proposed. The activation energy is determined from a nonisothermal measurement made by differential scanning calorimetry and an aging test at a single elevated temperature. The use of the onset temperature of the exothermal peak is proposed to evaluate the activation energy of the degradation of the PP film. Four types of PP film capacitors were thermally aged at 100 degrees C for different aging times. For each aging time, the capacitance was measured at different frequencies. According to the standards, two end-of-life criteria (2% and 5%) were imposed for the reduction in the capacitance. The parameters of the lifetime line a and b were determined, and finally, the lifetime values were calculated. The novel proposed method is effective in terms of both energy and manpower costs compared with the current method, which uses three aging temperatures.

Capacitors manufactured from the polypropylene film are high-quality components having a very low loss factor and nonlinearity of the current-voltage characteristic. Dependence of these parameters on the time of thermal aging of the PP capacitors at the temperature100 oC were inspected. It was found small deteriation of the loss factor and more significant changes of the nonlinearity during long-time aging at this temperature.

Model degradace kondenzátorů s metalizovanou elektrodou Predikce životnosti, testování a měření parametrů foliových kondenzátorů

The article describes the analysis of a possible influence of a measuring circuit on the results of the OCVD method. The influence of further junction parameters on effective carrier lifetime measurements is evaluated, which has not been currently monitored by the OCVD method. Then the influence of the exciting current generator, exciting current waveform and parasitic properties of the generator is searched. A especial emphasis is given on the impedance matching between an analysed PN junction and an evaluating part of a measuring circuit. A simulation algorithm expressing the processes both in the tested junction and measurement circuit was found. The measuring system was implemented in several variants and typical measurements were carried out. For experimentally determined parameters, the simulations, whose results showed a good compliance with the results of the experiments, were performed.

Capacitors made of a polypropylene film are high-quality components having self-leading ability and low loss factor. The work was oriented on study of percentage changes of the loss factor of the PP film capacitors during long-time thermal treatment at 100 oC. The capacitance of the capacitors was 100 nF, the class of the capacitors was X2. The loss factor was inspected at the frequency of 1 kHz, 10 kHz, 100 kHz and 1 MHz. It was found low changes of the loss factor only that depend slightly on the value of the loss factor at the beginning of the test.

This article describes both the design and construction of the switch that enables switching with a high di/dt rate and a special type of a shunt for measuring current. A designed circuit is based on a parallel connection of high power MOSFET transistors with independent drivers. Negative influence of parasitic inductions of transistor leads was analyzed. Film capacitor testing is based on applying a very fast discharging process. Current and voltage waveforms arising during the measurement are used to create an equivalent circuit of the capacitor.

Polypropylene film capacitors manufactured by five different manufacturers were aged at the temperature of 100 deg. of C for 1600 hours. Changes of the capacitance the loss factor and nonlinearity of the current-voltage characteristic were examined during ageing.

Capacitors of metalized polypropylene film are components that cover a wide range of capacitances. The have a very low loss factor and extremely long lifetime.

The goal of this work was to test ageing of capacitors with metalized polypropylene film by the sinusoidal and non-sinusoidal voltage and to find if the shape of the voltage waveform influences the ageing rate.

This paper summarizes the results of metalized film capacitor analysis made on capacitors of different manufacturers and types. The capacitors were operated for about 12 years in a power supply and served as a reactance to reduce the supply voltage without losing active energy. The capacitors were long stressed by continuous presence of voltage and current pulses. The measured results are reviewed and the causes of excessive aging of capacitors, including photographs and X-ray analysis of defects are discussed.

PP capacitors are capacitors of s special type, which makes self-healing of the capacitor possible. These capacitors are components of high quality with very low loss factor. The testing was carried out by the electrical stress. It was found that the changes are higher if the component is loaded by the AC or pulse voltage than DC load.

Polypropylene film capacitors were aged and the AC voltage and nonlinearity of their VA characteristic was investigated as a function of the time and other conditions of ageing. It was found that nonlinearity of the capacitors increases with the time of ageing and with the level of the voltage. It was also found that this parameter is more sensitive to the ageing of the component than the capacitance or the loss factor, what are the parameters, which are normally investigated.

Abstract - All electronic equipment where large S/N ratio is requested for the signal processing is very sensitive on disturbances coming from power supplies. This is especially true for high accuracy measurement equipment. Then simple solution is to feed such equipment from accumulators or batteries; nevertheless, this brings problems with their servicing. This contribution presents the results of study of noise disturbance of laboratory power supply on high pure sine-wave signal source and describes a design of realized special power supply with minimum noise.