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Wetting and Spreading of Solder on PCB Surface
Wiesner, Lukáš ; Špinka, Jiří (referee) ; Starý, Jiří (advisor)
This work deals with the metal surface wetting problems of molten lead-free solder and monitoring of ongoing processes at the inter-phase interface. This work also deals with flushing monitoring of spreading velocity on solder finishes Ni/Au and Immersion Sn deposited on copper plated base material FR4 using digital cameras. Measurement is performed at the improved workplace. After the reflow process is measured by length of spreading solder. It evaluates and compares the time dependence of velocity of spreading solder for Ni/Au and Immersion Sn finishes.
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WETTABILITY OF PCB SURFACE FINISHES
Minář, Jan ; Jana, Toulová (referee) ; Starý, Jiří (advisor)
This bachelor’s thesis with measuring of wetting characteristics by the wetting balance method for samples of different surface finishes from the firm Gatema. It deals with influence of the isothermal aging and reflow processes on wetting characteristics of surface finishes ENIG, HAL and immersion tin. The influence of intermetallic layer on the overall wettability is studied in case of the surface finish of immersion tin. Also deals with the wettability of the nickel layer, after stripped off gold, in case of the surface finish of ENIG.
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Wetting and Spreading of Liquid Solder on Metal Surface
Kučera, Lukáš ; Špinka, Jiří (referee) ; Starý, Jiří (advisor)
This work deals with the metal surface wetting problems of molten lead-free solder and monitoring of ongoing processes at the inter-phase interface using the method of evaluation of the height of the molten solder deducted from the video sequences. The work is aimed at evaluating the metal surface wettability, wetting angle determined. Wettability of the metal surface is compared for different types of surface treatments and for different ages of the measured samples. Measurement is performed at the improved workplace, is used to evaluate the newly derived formula for calculating the wetting angle and created program for automatic evaluation of Picture is used to.
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Compatibility of piezoelectric semicrystalline polymerand osteoblastic cells
Havlíková, Tereza
For the improvement of tissue regeneration,functional polymer scaffolds that can mimic the extracellularmatrix of human tissue are extremely desirable. Depending on thetissue that the scaffolds are intended to resemble, these scaffoldsmust satisfy highly precise requirements such as non-toxicity orfibrous structure. High piezoelectricity and hydrophilicity alsoproved to have convenient effects. Due to their innate capability tocreate surface charges under mechanical stress, piezoelectricmaterials such as polyvinylidene fluoride (PVDF) become excellentcandidates for creating functional scaffolds. It is desired for PVDFto also have hydrophilic properties. Otherwise, it could preventadequate cell adhesion and growth necessary for the constructionof biomimetic scaffolds. For this study, electrospinned PVDFnanofibers covered by human or mouse osteoblasts were subjectedto Raman spectroscopy, measurement of the contact angle of theliquid wettability on the sample surface to observe hydrophobicityand hydrophilicity, and scanning electron microscopy (SEM) toassess properties of the material in relation to oxygen plasmatreatment.
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Vliv plazmového výboje na smáčivost semen vybraných kulturních plodin
PIHERA, Pavel
This bachelor thesis deals with the influence of atmospheric (Gliding arc) and low-pressure microwave plasma discharge on the surface of common wheat (triticum aestivum), annual sunflower (helianthus annuus), and pea (pisum sativum) and how the use of plasma discharge affects the ability of water to adhere to the seed surface. In this paper, the wettability of seeds before and after the use of plasma discharge is measured. The wettability is measured according to the angle of the drop applied to the measured seed.
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Plasma treatment impact on physical and chemical properties of polymeric fibers
Hlůžek, R. ; Prošek, Z. ; Trejbal, J. ; Fládr, J. ; Potocký, Štěpán
Presented work focuses on chemical and physical properties of plasma modified polymeric macro-fibers. Polyethylene terephthalate (PET) and polypropylene (PP) fibers having approx. 300 mu m in diameter were modified using cold oxygen plasma in order to achieve their surface changes needed for durable bond and adhesion with cement matrixes. A duration of plasma modification differed between 5 to 480 seconds, where an effect of the treatment was examined. Fiber surfaces chemical changes were researched via wettability measurement with demineralized water (the measurement was repeated immediately and after 1, 7 and 30 days to find out the changes stability). Physical changes were studied by means of weight balance (determination of weight loss) and tensile strength tests. It was found that wettability was enhanced significantly - up to two times, while mechanical properties of treated fibers decreased only slightly.\n
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Development of dual technology for the treatment of winter rape and spring barley seeds
OLŠAN, Pavel
The dissertation thesis deals with the use of low-temperature plasma and biological treatment of winter rape seed and spring barley as an alternative to chemical dressing in relation to the Decree on Integrated Pest Management 205/2012 Coll. The seed treatment technology is conceived as a two-phase process, where a lowtemperature plasma discharge of the Gliding Arc type ignited in the air at atmospheric pressure is used in the first step and a biological preparation containing spores of Trichoderma virens is applied to the treated seed as the second step. The plasma discharge treatment allows to increase the wettability of the seed surface, which improves the adhesion of the biological preparation in the second treatment step. Plasma also enables to activate selected processes taking place in seeds, which support their germination and subsequent growth. The content of the dissertation is divided into four sub-units which are mutually related: 1. determination of plasma discharge parameters for subsequent applications in the proposed technology, 2. carrying out laboratory experiments to assess the effect of plasma on seed, 3. carrying out field experiments to compare crop yields for different seed treatment options, 4. proposal for a regulation for seed treatment in a continuous mode by plasma discharge followed by application of the preparation and production of a functional sample. The work is markedly interdisciplinary and intervenes in the field of plasma physics, chemistry, plant production and construction of technical equipment. From the results achieved we can give a short summary: 1. Plasma discharge treatment of winter rape and barley seeds results in increased surface wettability. 2. No difference in the absorption of plasma treated and untreated seeds was observed during the experiments. 3. Developed dual seed treatment technology has the potential to increase yield. The dissertation thesis was realized within the project TA04021252 ? "Development of equipment for physical treatment of seeds and malt using low-temperature plasma."
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Plasma treatment of fabrics
STEHLÍK, Radim
The thesis deals with the surface modification of cotton fabric by low-pressure micro-wave plasma discharge. The main materials used for this experiment are cotton fabrics and hexamethyldisiloxane. The experiment itself is focused on the modification of cotton fabric to improve hydrophobic atributes. An argon process gas was used in the surface modification. The individual treated samples were operated with changes in process gas flow and the time during which the above-mentioned modifications was performed. Two methods were used to analyze the results of the experiment. The first one was aimed at determining changes in hydrophobic atributes in the form of wetta-bility in an unmodified sample compared to other modificated samples using the drop-let method. An electron microscope was used for the subsequent study of possible changes in surface topography. From the point of view of the examined results, the difference in hydrophobic properties was observed when using the droplet method to-gether with the change in the topography of the surface obtained on the electron mi-croscope in the cotton samples examined. The actual evaluation of individual methods points to the desirable changes in modified cotton compared to unmodified cotton. Further information regarding the results of the experiment, depending on the changes in individual parameters in the cotton treatment process using low pressure microwave plasma discharge, are presented in thesis.
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