|
|
Influence of printed board surface finishing on solderability with vapour soldering
Matras, Jan ; Starý, Jiří (referee) ; Šandera, Josef (advisor)
Thesis deals with vapor soldering and wetting the surface with solder during the soldering process. It describes in detail the advantages and disadvantages of various surface finishes on the PCB. Generally characterizes the properties of lead-free solders and fluxes. Describes vapor soldering process, including the properties of the liquid itself. It also focuses on a method of evaluating the wettability by using solder balls and its performance on individual samples surface finishes.
|
|
|
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.
|
|
| |
|
|
Study of gecko adhesion force and formation of a nanostructured gecko mimicking surface
Vyskočilová, Marta ; Hubálek, Jaromír (referee) ; Neužil, Pavel (advisor)
This thesis deals with the surface of a gecko in relation to its adhesion ability. Understanding the mechanism of movement and adhesion principle is important for the design and manufacture of nanostructured material. Likewise, knowledge of the origin of the self-cleaning ability allows the description of the influence of surface structure on movement and forces acting at the contact. The work describes the process of making nanostructured surface, which was modified in order to obtain maximum adhesion forces. The material properties were determined by the values of wettability and by force spectrum measurement. Their results were compared with the theoretical assumption of capillary forces and other possibilities to increase adhesion.
|
|
|
Surface free energy of plasma polymers
Klepáčková, Barbora Bella ; Dzik, Petr (referee) ; Čech, Vladimír (advisor)
Tato práce se zabývá studiem změn volné povrchové energie organokřemičitých plasmových polymerů na základě jejich rozdílných depozičních podmínek. Výpočet volné povrchové energie byl proveden pomocí Owens-Wendt-Kaelble, Wu a acido-bazické teorie. K měření kontaktních úhlů bylo použito čtyř různých testovacích kapalin (voda, formamid, dijodmethan a glycerol). Pro tenké vrstvy plasmového tetravinylsilanu připraveného s efektvním výkonem 2, 10, 25, 70 a 150 W byla naměřená volná povrchová energie mírně vzrůstající.
|
|
|
Technical and economic solving of barking knives
Novotný, Petr ; Hála, Michal (referee) ; Kubíček, Jaroslav (advisor)
The target of the study is theoretical explaining the condition of creation of the soldered point with regard to basic and additional mat. Below, the detailed analysis of the existing technical problem and consecutive design of the solution method.Content of the study is also technological process of production of the barking knife and choice of the efficient producer.
|
|
|
Optimization of electrochemical sensor for detection in microvolume
Gajdoš, Libor ; Pekárek, Jan (referee) ; Prášek, Jan (advisor)
This thesis describes optimization and modification of standard thick-film electrochemical sensor to be able to be used for detection in microvolumes. In the theoretical part, the thick film technology is described. The work is then focused on the wettability of surfaces followed by introduction to electrochemistry and electro-analytical methods. In the experimental part, screen-printing of various types of thick film pastes on ceramic substrates for determination of their wettability and the following modification of the sensors with thick-film paste and with Parylene vaporization can be found, as well as the basic electrochemical measurements in microvolume using the modified sensor. Finally the results are summarized in conclusion.
|
|
|
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.
|
|
|
Physical-chemical property characterisation of thin reflective layers on polymer substrates
Stružínský, Ondřej ; Dzik, Petr (referee) ; Krčma, František (advisor)
This work deals generally with surface diagnostic and optical properties of thin layers which are created by plasma polymerization of hexamethyldisiloxane monomer. The influence of oxygen adittion on thin layers properties was studied, too. This polymer layers are commercially made to protect reflective layers in the headlights. Thin layers were made in deposition chamber AluMet 1800V at Zlin Precision Company. Teoretical part of this work deals with methods which are used for deposition of thin layers, mainly physical (PVD) and chemical (PECVD, CVD) depositions. The conditions which influenced plasma polymerization itself are discussed as well as, monomers which are used for plasma polymerization and stability of thin polymer layers. Also there are mentioned the most frequent plasma processes diagnostic methods applicable during the deposition (optical emission spectroscopy) and methods for thin layers diagnostic (wettability, UV-VIS and infrared spectroscopy). Spectrometer Jobin Yvon Triax 320 was used for emission spectra acquisition during the plasma deposition. There were analyzed only two spectra created at same conditions as power at 3 kW and monomer flow rate at 100 sccm; the first one was in pure monomer, the second was obtained with oxygen addition of 150 sccm into the monomer flow. There was not found any essential differences between these spectra in the range 300 nm to 800 nm. Besides the thin layers analyzes after their formation, the samples were exposed to common aging conditions with respect to their use. One third of the prepared samples was exposed by ultraviolet radiation for 48 hours (exposure power of 0.68 W.m-2 at 340 nm) and the other part of samples was inserted for four days into NaCl solution of 50 g.l-1. The surface properties of layers were studied by their contact angle with three liquids (water, diiodmethane, and glycerol) that allowed their surface energy calculation. Results of this measuring are as following: Oxygen addition decreased contact angle of water after exposure of UV radiation. If the highest flow rate of monomer was used and oxygen was added, NaCl degradation did not have any significant influence on contact angle to water. Optical properties of prepared thin films were characterized by UV-VIS spectroscopy. Optical properties were measured only for samples after deposition and samples that were exposed by ultraviolet radiation. Results showed that oxygen addition into the reacting mixture increased the light absorption in UV-VIS (300-800 nm). The absorption was significantly increased after exposure of ultraviolet radiation. With respect to the application of these thin layers is necessary to say that this influence is undesirable. On the other hand, absorption of thin layers deposited at 2 kW, without oxygen addition and flow rate of monomer at 125 sccm a 150 sccm was decreased. Results of this work can be useful for investigation and study of deposited thin layers. The most useful can be with another work which deals with plasma diagnostics during the deposition even more closely. Then it will be possible to adjust and predict properties of deposited layers.
|
|
| |
guest ::
