Sabemos que em placas de circuito impresso montadas com tecnologia SMD Surface Mount Device podem ocorrer problemas com a migração eletroquímica. O fenômeno aparece principalmente porque os novos encapsulamentos possuem terminais com espaçamentos muito próximos. A migração eletroquímica pode tornar-se um potencial problema no processo de soldagem eletrônica quando é utilizado a tecnologia Lead Free na montagem das placas. O processo de migração eletroquímica ocorre quando temos metal, isolante e metal, em ambiente de alta umidade e sobre polarização elétrica, o metal deixa a posição inicial em forma de íon e se redeposita sobre o isolante. Em uma placa de circuito impresso, dois terminais adjacentes podem tornar-se eletrodos, dessa forma as dendritas crescem do cátodo para o ânodo. Podem aparecer diferentes morfologias com diferentes elementos envolvidos no processo de migração, dependendo da composição da pasta de solda ou acabamento da placa de circuito impresso. Uma estrutura do tipo pente comb feita sobre laminado FR4 foi utilizada nos experimentos. A distância entre as trilhas foram de 102 e 254 mícrons para simular uma distancia real dos terminais dos dispositivos. Os fatores considerados durante os experimentos foram: A distancia entre os terminais na estrutura (102 ou 254 mícrons), tensão aplicada (2 ou 3 V). Foi observado que a pasta de solda e o acabamento final não influenciam no processo de migração eletroquímica. O Estanho foi o principal metal que migrou. Todos os resultados obtidos nesse estudo concordam com a literatura. / It is well known that in printed circuits boards assembled by SMT technology may occur Electrochemical migration (ECM). This phenomenon appears mainly because the new packaging has the terminals very close. Also the Electrochemical migration may become a potential reliability problem in electronic soldering when lead free technology is used in soldering electronic devices. Electrochemical migration is an electrochemical process where metal on an insulating material, in a humid environment and under an applied electric field, leaves its initial location in ionic form and redeposit. In a PCB two adjacents terminal may behave as electrodes so the dendrites grow from cathode to anode. It can show different morphologies with the different migration elements involved depending on the solder paste composition or PCB surface finishing. A structure with a comb shape printed on FR4 substrate was used in the experiments. The distance between the fingers in the structure was 102 or 254 microns, in order to simulate a real distance between dispositive terminals. The factors considered during the experiments were surface finishing (ENIG or HASL), solder paste composition, distance between terminals (102 or 254 microns) and applied voltage (2 or 3 V). It was observed that the solder paste and the surface finishing dont influence the ECM process. Tin was the main metal that migrates. All the results obtained in these study agrees with the literature.

This work deals with effects of nanoparticles, mainly copper and silver, on properities of lead-free solder pastes. It describes basic tests done on solder pastes according to IPC-TM-650 standards. In practical section this work focuses on the preparation of Sn-Bi solder paste and the measuring of viscosity. After that different concentrations of silver copper alloy nanoparticles are added to the SnBi solder paste. These solder pastes are tested by the IPC standarts and mechanical and resistive tests are done on printed circuit boards where the effects of mixed in nanoparticles are observed.

This case study examined emitted sound and actuated piezoelectric current in a solderpaste jet printing machine to conclude whether quality degradation could be detected with an autoencoder machine learning model. An autoencoder was used to detect anomalies in non-realtime that were defined asa diameter drift with an averaging window from a target diameter. A sensor and datacollection system existed for the piezoelectric current, and a microphone was proposedas a new sensor to monitor the system. The sound was preprocessed with a Fast Fourier Transform to extract information of the existing frequencies. The results of the model, visualized through reconstruction error plots and an Area Under the Curve score, show that the autoencoder successfully detected conspicuous anomalies. The study indicated that anomalies can be detected prior to solder paste supply failure using the sound. When the temperature was varied or when the jetting head nozzle was clogged by residual solder paste, the sound model identified most anomalies although the current network showed better performance. / Denna fallstudie undersökte emitterat ljud och drivande piezoelektrisk ström i en jetprinter med lödpasta för att dra slutsatsen om kvalitetsbrister kunde detekteras med en autoencoder maskininlärningsmodell. En autoencoder användes för att detektera avvikelser definierade som diametertrend med ett glidande medelvärde från en bördiameter. Tidigare studier har visat att den piezoelektriska strömmen i liknande maskiner kan användas för att förutspå kvalitetsbrister. En mikrofon föreslogs som en ny sensor för att övervaka systemet. Ljudet förbehandlades genom en snabb fouriertransform och frekvensinnehållet användes som indata i modellen. Resultaten visualiserades genom rekonstruktionsfel och metoden Area Under the Curve. Modellen upptäckte framgångsrikt tydliga avvikelser. För vissa felfall visade ljudet som indata bättre prestanda än strömmen, och för andra visade strömmen bättre prestanda. Till exempel indikerade studien att avvikelser kan detekteras före lodpasta-försörjningsfel med ljudet. Under varierande temperatur och då munstycket var igentäppt av kvarvarande lödpasta identifierade nätverket med ljud som indata de flesta avvikelser även om nätverket med strömmen visade bättre prestanda.

This thesis deals with novel trends in solder paste technology. It focuses on nanoparticle applications used as a tool for improving a state of the art lead free solder alloys. The recently published results about the impact of different types of nanoparticles on properties of newly-emerged nanocomposite solders are discussed and summarized in the thesis. Preparation, practical application and testing of new solder paste based on low temperature SnBi alloy with an admixture of titanium dioxide are also discussed. Finally, properties of solder joints using these solder pastes are investigated and the results are evaluated.

Printed circuit boards (PCBs) are essential components in various electronic devices, playing a vital role in their functionality. Over time, PCBs have evolved significantly, becoming smaller, more complex, and multi-layered to meet the demands of advancing technology and consumer preferences. The quality of solder paste deposits is measured by circularity, volume, positioning, and the number of satellites. Mycronic is a supplier of jet printing machines for PCB manufacturers and needs to investigate and counteract an unwanted variation in volume and positioning within the first dot of the solder paste strip, and its so-called “sea saw” effect for the following three dots.  This master’s thesis has two aims. The first aim is to develop and evaluate an experimental method to reduce variation between the dots in the strip. The second aim is to reduce the variation between the 1st dot and the following three dots by finding a combination of pre-feed, first, second, and third waveforms to obtain improved precision, volume, circularity, and reduced volume variation. Using an experimental design a full factorial design was used, examining six experimental factors. The design was further augmented with a central composite design to describe the second-order model. The knowledge from the experiment was used to optimize and improve the quality factors of jet printing, which were verified with an additional experiment. The results of the study provided compelling evidence that only the selected experimental factors had a significant impact on improving the volume metric. It was observed that the presence or absence of satellites during the experiment did not have any effect on the results, and neither did the positioning and circularity factors contribute to any improvement or deterioration. Specifically, the most significant difference in volume between 1st and following three dots for the optimized solution is 0.5 nl, and the currently used settings have a difference of 2.65 nl. The experimental approach employed in this master's thesis holds excellent promise for Mycronic, as it paves the way for the future development of piezo-actuation profiles (i.e. specific settings for the jet printer). The potential contributions to the industry are significant, particularly in terms of advancing the methodology for investigating and enhancing the quality metrics of piezo-actuation profiles through experimental means. This research opens up new avenues for Mycronic to refine its printing processes and improve overall print quality, ultimately leading to better outcomes for their customers.

Thesis is focused on the effect of heating factor on quality of solder joints. In theoretical part is solved reflow soldering technology, problematice of solder paste choice or criteria of soldering profile setting. The practical part is dedicated to demonstrating the impact of heating factor on solder joint quality. There are used X-Ray analysis, microsections and electron microscopy. In the final part of this thesis are summarized knowledge from theoretical part and experimental obtained results to defend of next steps in diploma thesis.

<div> <div> <div> <p>Transient liquid phase sintering (TLPS) technologies are potential low-temperature solders for sustainable replacements of lead-based solders and high-temperature lead-free solders. Compared to solid-state sintering and lead-free solders, TLPS uses lower temperatures and is, thus, suitable for assembling temperature-sensitive components. TLPS is a non- equilibrium process and determining the kinetics is critical to the estimation of processing times needed for good joining. The tin-indium (Sn-In) system with a eutectic temperature of 119°C is being considered as the basis for a TLPS system when combined with tin. Most models of TLPS include interdiffusion, dissolution, isothermal solidification, and homogenization and are based on simple binary alloys without intermediate phases. The Sn-In system has two intermediate phases and thus the reaction kinetics require additional terms in the modeling. Differential Scanning Calorimetry (DSC) has been used to measure the response of Sn-In alloys during the transient liquid phase reaction. Preparation of tin indium alloys for microstructural analysis is challenging due to their very low hardness. This study uses freeze-fracturing of the tin indium alloys to obtain sections for microstructural analysis. The combination of DSC and microstructure analysis provides information on the reaction kinetics. It was observed that the solid/liquid reaction does not proceed as quickly as desired, that is, substantial liquid remains after annealing even though the overall composition is in the single-phase region in the phase diagram. </p> </div> </div> </div>

Despote the indisputable advantages of fine-pitch components, is need to calculate with a few trouble during production, especially increased requirements for accuracy of mounting and solder printing. In this work I’m concerned with problems of solder printing for these components and evaluation using SPC. For the evaluation I used 3D paste inspection based on laser scanning of the surface. The output of this work is to describe the principles of solder printing and elaborating of GR&R, SPC analysis and histograms of solder printing for some outputs. I focused in my master thesis on motive design change of problematic components and economic evaluation of the adjustments.