Search

This article will present results of activity testing of rosin fluxes. A good solderability of a component output and a soldering pad of PCB are important for the creation of a quality joint. Since it supports a melted solder wetting on a soldered surface, a flux has a definitive influence on the creation of a quality joint. Further, it removes oxides and other impurities from soldering alloys and prevents from a creation of a new oxide layer during soldering. According the technology of a solder joint creation, a flux is added into the soldering process in different ways. The aim of the test was to select a rosin flux having with the solder tube the best results during soldering of the copper surface on PCB's. Fluxes were compared by the help of two different tests. The first trial was carried out by the area of spread method, since this test is suitable for solderability testing of materials and comparison of a flux activity. The wetting balance test was chosen as the second trial. This method enables to measure the wetting force affecting the tested sample. Curves of wetting forces are the test result serving for comparison of single fluxes.

We are grateful to the scientific grant agency of the Ministry of Education, Science, Research and Sport of the Slovak Republic for financial support of project VEGA No. 1/0947/16. In this experimental work we examined the temperature and mechanical stress in the thin films of microelectronic structures based on GaN and AlN by Raman spectroscopy. The rise in temperature in the Raman spectrum is shown by shifting the Raman bands toward lower wavenumbers. Similarly like with changes of temperature, the changes of the positions of Raman bands may indicate the changes of mechanical stress in the structure. It was confirmed experimentally that in the case of tensile stress the Raman bands are shifted towards lower wavenumbers, and under compressive stress to higher wavenumbers.

Článek se zabývá studiem vlastností aprotických elektrolytů pro lithno – iontové systémy. Byla změřena teplotní závislost měrné vodivosti elektrolytů od pokojové teploty do 90 °C a stanovena materiálová konstanta α a zdánliva aktivační energie Ea. Jako rozpouštědla pro elektrolyty byly použity dipólové rozpouštědla s relativní permitivitou v rozsahu 2 až 3 dimethyl karbnoát (DMC) a diethyl karbonát (DEC) a silně dipólové rozpouštědla s relativní permitivitou v rozsahu 40 až 90 sulfolan (SL), propylen karbonát (PC), ethylen karbonát (EC), dimethylsulfoxid (DMSOX). This paper deals with aprotic electrolytes properties for the lithium ion systems. The temperature dependence of specific conductivity was measured and that form room temperature to 90 °C. The material constant α and activation energy E a were determined. Dipole and strong dipole solvents were used for measurement. The dipole solvents with relative permittivity 2 to 3 dimethyl carbonate (DMC) and diethyl carbonate (DEC) were used. The strong dipole solvents with relative permittivity 40 to 90 sulfolane (SL), propylene carbonate (PC), ethylene carbonate (EC) and dimethyl sulfoxide (DMSOX) were used.

The thermal stability of p-type CdTe crystals by using conductivity and Hall-effect measurements have been studied at room and slightly increased temperatures. Different types of thermal relaxation were observed for two p-type samples, which differed in the character and in the rate of the relaxation.

Aluminum nitrides layers prepared on sapphire substrates are examined. The substrate surface was treated by dry plasma etching. The morphology of aluminum nitride thin films was studied by atomic force microscopy. Lateral force atomic force microscopy was used to study the morphology heterogeneity. The dependence of films morphology on the formation conditions has been defined. The objective of the study contributes to the improvement of technological process of dry etching and film deposition.

This work aims to determine the suitability of use of low-temperature co-fired ceramics (LTCC) and thi ck film technology in applications with semiconductors base d on SiC and GaN, which have high operating tempera ture. Especially, Heraeus HeraLock 2000 substrate is inve stigated. The paper is mainly focused on the behavi our and reliability of wire-bonds, which are used for conne ction of the above-mentioned semiconducting devices with a circuit or a package. A test sample was designed for this purpose, which was subjected to thermal lo ad. Subsequently, changes in the bonds resistivity were studied, together with their strength and any defe cts caused by the thermal load. Other properties, such as term omechanical stress of the material for different te mperature profiles were simulated in the ANSYS software. Crea ted mathematical model simulated and compared differences between gold and aluminium wire-bond.

Průmyslové experimenty jsou základním nástrojem pro zajištění kvality výroby. Nezastupitelnou roli mají především při prvotním vývoji daného výrobku a při následném zlepšování kvality. Je třeba použít systematický návrh experimentu, aby na jeho vyhodnocení mohyl být použity statistické metody. Základními statistickými metodami pro hodnocení experimentů jsou regresní analýza a analýza rozptylu ANOVA. Cílem tohoto článku je čtenáři poskytnout základní přehled o analýze rozptylu a jejího použití ve vyhodnocování experimentů. Industrial experiments are a fundamental tool to ensure quality production. It has an essential role especially in the initial development of the product and the subsequent quality improvement. For statistical evaluation is necessary to use a systematic design of the experiment. Basic statistical methods for the evaluation experiments are regression analysis and analysis of variance ANOVA. The aim of this paper is to provide the reader an overview of the analysis of variance and its use in evaluation of experiments.

In the paper main consideration is paid to investigation of inhomogenities in dielectric sample from the standpoint of their impedance properties and reflected signal amplitude. Such application include inspecting modern materials such as composites, detecting and characterizing surface and volume flaws, and evaluating the compressive strength of cement structures.The paper deals with measurement of reflex coefficient in dependence on crack depth on dielectric samples on microwave frequencies from the X –band. Evaluations are made by means of quantities used in microwave technique. Obtained quantities are compared with each other and also with analogous to the quantities measured at the same conditions on metal sample.