Abstract Carbon nanotubes (CNTs) have fascinating mechanical, electrical and thermal properties, all of which significantly depend on structural properties such as nanotube length, number of walls, lattice defect densities, impurities and surface functional groups. A number of different applications of carbon nanotubes have been demonstrated during the past two decades including electrical interconnects, transistors, heating and cooling devices, sensors and various actuators. However, further studies on the structure-dependent properties and innovative handling techniques of these materials are needed in order to explore the limitations of use and to be able fully to exploit the advantageous properties of such one-dimensional sp2 hybridized carbon nanomaterials. In this thesis, random networks of single-wall and multi-walled carbon nanotubes (SWCNTs and MWCNTs, respectively) and aligned films of multi-walled carbon nanotubes are studied in the context of three main application fields: gas sensing, electrical interconnects/electrodes and thermal cooling elements. Analyses of associated material properties and some feasible integration techniques are discussed. Single-wall and multi-walled carbon nanotube films cast from aqueous dispersions are shown to be selective nitric oxide sensing components in Taguchi-type sensor devices, in which films based on SWCNTs outperformed those made of MWCNTs. The thickness dependent electrical conduction mechanism of inkjet-printed SWCNT films is also discussed. Robust aligned MWCNT films are demonstrated as soft electrical contact brushes in DC motors and in other moving electrical contacts. The thermal properties of freestanding aligned MWCNT forests are analyzed and shown to be potential alternatives to copper or aluminium in the thermal management of electrical components. / Tiivistelmä Hiilinanoputkien kiehtovat mekaaniset, sähköiset ja lämmönjohto-ominaisuudet ovat kiinnostaneet tutkijoita suuresti viimeisten kahden vuosikymmenen ajan. Monia erilaisia applikaatioita on demonstroitu tänä aikana: mukaan lukien sähköiset kontaktit, transistori-rakenteet, lämmitys- ja jäähdytyslaitteet, anturirakenteet sekä erilaiset aktuaattori-rakenteet. Tämän väitöskirjan päätavoitteena on tutkia hiilinanoputkien toiminnollisuutta ja käytännöllisyyttä erilaisissa sovelluskohteissa. Tässä työssä käytettävät hiilinanoputkirakenteet ovat joko satunnaisjärjestyksessä olevia nanoputkista koostuvia verkostorakenteita tai yhdensuuntaisia, makroskooppisia hiilinanoputkikalvoja. Nanoputkia tutkitaan kolmessa erityyppisessä sovelluskohteessa: kaasuanturisovelluksessa, sähköisissä kontaktirakenteissa sekä jäähdytyselementteinä. Työssä analysoidaan hiilinanoputkirakenteiden ominaisuuksia eri sovelluskohteissa sekä esitetään joitain käyttökelpoisia tekniikoita hiilinanoputkien integroimiseen olemassa oleviin tekniikoihin. Hiilinanoputkien osoitetaan olevan käyttökelpoisia aktiivisia materiaaleja typpioksidille resistiivisessä kaasuanturirakenteessa. Tulosten perusteella yksiseinämäiset hiilinanoputket ovat moniseinämäisiä herkempiä ja parempia kyseisessä sovelluksessa. Lisäksi tutkitaan ja analysoidaan mustesuihku-tulostettujen yksiseinämäisten hiilinanoputkifilmien sähköisten ominaisuuksien riippuvuutta filmin paksuudesta. Vantterien yhdensuuntaisten moniseinämäisten hiilinanoputkirakenteiden osoitetaan toimivan erinomaisesti pehmeinä sähköisinä kontaktielementteinä liikkuvissa sähköisissä kontakteissa. Vapaasti seisovien yhdensuuntaisten, moniseinämäisten hiilinanoputkirakenteiden lämmönjohto-ominaisuuksien tutkiminen ja analysointi osoittaa, että kyseisiä rakenteita voidaan käyttää tehokkaina jäähdytyselementteinä ja mahdollisesti korvaavana vaihtoehtona alumiinille ja kuparille sähköisten komponenttien lämmönhallinta sovelluksissa.

Master’s thesis in the theoretical part analyses the heating factor (Q), which has significant share on quality of a solder joint. The practical part describes the design and production of test PCB and setting temperature profiles, SMD resistors soldering by using BiSn solder paste. Shear tests of SMD solder joints were realised and evaluated including isothermal ageing samples. At the end of master’s thesis solder joints visual aspects and defects were evaluated, measurement thickness of intermetallic compound by not only optical microscope but also SEM, discussion about results and Q was evaluated.

This master‘s thesis deals with the design of battery powered soldering iron. The soldering iron will be placed in the plastic box from a conventional transformer soldering iron. First, we need to find the parameters of the original transformer soldering iron. Then design a synchronous step-down converter, driver of converter, BMS circuits, and component placement in a plastic box. The battery-powered soldering iron was successfully revived and tested, the final parameters of the converter are: voltage 0.4 V at 80 A current. The total power on the soldering wire is 32 W. Technically, this is a very interesting alternative to the classic version of the soldering iron, which can be used for assembly or repairs in poorly accessible locations.

This thesis is considered about interconnect PCB with microelectronic and electronic modules and continuing on thesis MODERN CAUSES OF ASSEMBLY MICROELECTRONICS AND ELECTRONICS MODULES. This thesis includes, definition of termomechanical strain in solder joints and description of LTCC technology. Practical part includes characterization the causes of assembly with usage chip component and proposal footprint for PCBs, modules and results of temperature cycling of tested modules.

This master´s thesis deals with problems of wave soldering and application methods Design of Experiments for the new product production. Summarizes the basic knowledge of soldering technology, of solder alloys and Design of Experiments methods. Design of Experiments method has been applied to product to find the optimal for wave soldering setting.

This master´s thesis deals with QFN packages soldering and technology procedures optimization. The aim of theoretical part is description of QFN packages, their assembly and reflow soldering on PCB in HONEYWELL. The aim of the practical part is to propose a method of measuring temperature and optimizing the thermal profiles of selected PCB with QFN packages by using convection (HONEYWELL) and infrared (BUT) reflow ovens. Comparison and evaluation of thermal profiles for 3 production PCBś with QFN packages using solder paste AIM NC257-2 were realised. The main part of master´s thesis are appearance evaluation of solder joints, preparing microsection and measuring intermetallic layers thickness by using the optical and the scanning electron microscopes, analysation and study of QFN defects created during soldering proces. These tests were performed with 2 production PCB´s. Optimization of SPI and soldering technology procedures where were analyzed QFN packages were processed on one type of PCB. Interesting part of this diplomma thesis is creating of the 3D heat transfer model of QFN package during the reflow soldering in SolidWorks.

Cette thèse vise à réaliser des développements théoriques et numériques portant sur le comportement en cyclage thermomécanique de nouveaux alliages de brasure. L’objectif est de proposer une méthodologie de simulation de la fatigue des assemblages électroniques intégrant ce type de brasures. De nombreux modèles semi-empiriques de fatigue existent déjà mais ont montré leurs limites pour une prédiction suffisamment précise de la fiabilité. Il existe donc un besoin d’enrichir les approches existantes par une description des mécanismes de défaillance à l’échelle mésoscopique, en prenant en compte la microstructure fine de l’alliage d’étain. Une formulation décrivant la plasticité cristalline de l’étain et l’endommagement aux joints de grains a donc été développée et intégrée dans un code de calcul pour simuler les mécanismes de déformation dans le joint de brasure. / This thesis aims to carry out theoretical and numerical developments on the thermo-mechanical cyclic behavior of new solder alloys. The objective is to propose a methodology for modeling the fatigue of electronic packages including this type of solders. Several semi-empirical fatigue models already exist, but have shown their limitations for an accurate sufficiently prediction of reliability. Therefore, it requires to enrich the existing approaches by a description of failure mechanisms in the mesoscopic scale, taking into account the fine microstructure of the alloy of tin. A formulation describing the crystal plasticity of tin and the damage of grain boundaries has therefore been developed and integrated in the finite element code for simulating the fracture mechanisms of solder joint.

L’analyse de la durée de vie des joints brasés est un challenge pour les industries du spatiale, de l’aéronautique et de la défense qui ont besoin d’équipements très fiables pour des environnements sévères et de longues durées de vie. L’évolution des technologies de boitier électronique, principalement conduite par les marchés civils, introduit de nouvelles architectures et de nouveaux matériaux dont la fiabilité doit être étudiée pour les exigences de ces marchés critiques. Un des éléments critiques d’une carte électronique est l’interconnexion effectué par le joint brasé. Dans ce contexte, les connaissances des propriétés de fatigue des matériaux utilisés pour le joint brasé sont nécessaires pour développer des cartes électroniques, définir les essais accélérés de qualification ou pour réaliser des simulations de durée de vie.Les lois utilisées communément dans l’industrie sont généralement des critères simplifiés comme les lois de Coffin-Manson, basée sur la déformation inélastique, ou Morrow, basée sur l’énergie dissipée. Les déformations plastique et visqueuse sont dans ces lois indissociées et appelées déformation inélastique, supposant que les contributions au dommage des déformations plastique et visqueuse sont similaires. Cependant, la pertinence de ces lois dans le cas du matériau joint brasé et les profils de mission des marchés critiques doit être étudiée. En effet, le joint brasé possède une température de fusion faible qui entraine un comportement visqueux même à température ambiante. Celle-ci est nécessaire à l’étape d’assemblage des boitiers. Ainsi, d’importantes déformations visqueuses sont développées notamment pour les environnements sévères et les longues phases de maintien de ces marchés critiques. Dans ce contexte, il est important de prendre en compte l’interaction fatigue-fluage dans les matériaux joint brasé pour atteindre les exigences de ces applications.Les limitations de la littérature sont le manque de données expérimentales précises dissociant les déformations plastique et visqueuse en essai de fatigue. La représentativité des éprouvettes massiques par rapport à l’application finales est en effet discutable au vue de la microstructure très spécifique du joint brasé. De plus, il n’existe pas de consensus réel sur les modèles matériaux à utiliser. Dans ce contexte, un banc de mesure a été développé dans le but de réaliser des essais de fatigue en cisaillement sur des boitiers électroniques assemblés.Le temps de maintien, la température et la force appliquée ont un impact sur le nombre de cycles à défaillance. La combinaison d’une augmentation de la température avec l’ajout du temps de maintien réduit jusqu’à un facteur dix le nombre de cycles à rupture. Les courbes d’hystérésis du boitier ont été converties en contrainte et déformations plastique et visqueuse dans le joint brasé dans le but de calibrer un modèle matériau et une loi de fatigue. Les résultats montrent que l’intérêt des lois de fatigue utilisées communément est limité. Des résultats utilisant différents dispositifs expérimentaux de la littérature ont été ajoutés pour compléter ceux trouvés. Une loi de fatigue modifiée en fréquence a été testée et montre de meilleures prédictions dans le cas d’essais réalisés à différentes fréquences car elle permet de prendre des effets liés au temps comme la viscosité. Cependant, des limites avec cette loi ont été trouvées dans le cas de sollicitation avec temps de maintien. Une loi de fatigue prenant en compte l’interaction fatigue fluage a ensuite été proposée avec de bonnes prédictions notamment pour des températures plus élevées. L’évolution de la microstructure a montré que le dommage détruit la structure dendritique du joint et la remplace par des joints de tailles plus petites dans la zone proche de la fissure. La coalescence d’éléments a également été observée. Cependant, plus d’investigations sont nécessaires pour définir les marqueurs spécifiques des dommages plastique et visqueux. / Solder joints reliability analysis represents a challenge for the aerospace and defense industries, which are in need of trustworthy equipment with a long lifetime in harsh environments. The evolution of electronic packages, driven by consumer civil applications, introduces new architectures and materials for which reliability needs to be qualified for the constraints of the aerospace and defense applications. One of the most critical elements of an electronic assembly is the solder joint interconnection. In this context, the knowledge of fatigue properties of solder material is required to design the assemblies, to define accelerated tests or to perform lifetime simulations.Fatigue laws used commonly in the industry are generally simplified criteria such as Coffin-Manson relation, based on inelastic deformation, or Morrow relation, based on dissipated energy per cycle. Cyclic creep and plastic strains are mingled and formulated as a unique inelastic strain in these relationships. The underlying assumption is that damage contributions of creep and plasticity phenomena are equivalent. The relevance of these laws in the case of solder joint and the mission profiles of aerospace and defense industries can be discussed. In fact, solder joint materials have low melting temperatures which are required by the assembly manufacturing process, inducing viscous strains even at room temperature. In this context, important viscous strains are developed due to the harsh environment with high temperatures and the long maintain phases of space, defense and avionics industries. Creep-fatigue interaction must be taken into account for solder joint material in order to address these applications requirements.Limitations of the literature are the lack of clear experimental data separating plastic and creep strains during fatigue tests. Representativeness of experimental tests based on bulk samples can be discussed because of the complex microstructure of solder joints. No consensus exists on the mechanical model and the parameters. In this context, an innovative test bench has been developed to perform shear fatigue tests with assembled electronic packages in order to study creep-fatigue interaction in solder joints.Dwell time, temperature and force have an impact on the number of cycles to failure. Combined increase of temperature and dwell time reduces the number of cycles to failure until a factor of 10. The hysteresis response of the package is converted in stress and plastic and viscous strains in order to calibrate a viscoplastic model and a fatigue law. Results show limitations of classic Coffin-Manson fatigue law. Experimental results from the literature have been used to complete our test plan. A frequency modified fatigue model shows increased prediction accuracy for fatigue tests performed at different frequencies. In fact, time-dependent viscous damage is included in the law by the frequency factor. However, limitations of this law have been found in particular for long dwell time configuration. A creep-fatigue model is proposed to dissociate damages from plastic and viscous strains. This fatigue law increases prediction accuracy in the case of high temperature and long dwell time configuration. Microstructure evolutions indicate the destruction of the dendritic structure and replaced by small grains recrystallization in the area close to the fracture. Coalescence of different precipitates is also observed in the damaged area. More investigations on this topic are required in order to evaluate the specific markers of plastic and viscous damages.

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.

<p>A wide variety of phase evolution phenomena observed in solids such as intermetallic growth at the junction between two metals subjected to high temperature, growth of oxide on metal surfaces due to atmospheric exposure and void evolution induced by electromigration in microelectronic devices for example, can be classified as being driven by reaction-diffusion processes. These phase evolution phenomena have a significant impact on material reliability for critical applications, and therefore, there is a requirement for modeling such reaction-diffusion driven phase evolution phenomena. It is difficult to analyze these due to the complexity of modeling the evolving interface between solid phases. Additional complexity is  due to the multi-physics nature of the diffusive and reactive processes. Diffusion in solids is driven by a variety of stimuli such as current, temperature and stress, in addition to the chemical potential. Therefore, there is a need for a model that accounts for the influence of such factors on phase evolution. In this thesis,  a generalized continuum based reaction-diffusion theory for phase and void evolution in solid state is developed. The derivation starts off with generalized interface balance laws for mass, momentum and energy. The thermodynamic entropy inequality for irreversible phase growth is derived for arbitrary anisotropic and inhomogeneous surface stress. These interface relations are combined with governing relations in the material bulk for the temperature, stress, electrical and concentration fields, to develop a general model capable of analyzing and describing phase evolution in solids. This theory is then applied to a variety of intermetallic phase and void evolution phenomena observed in microelectronics.</p> <p><br></p> <p>Electromigration induced voiding in thin metal films is an example of phase evolution that is an important reliability concern in microelectronics. Studies have reported that the electromigration induced void growth rate is inversely related to the adhesion of metal thin films with the base and capping layers. Electromigration experiments are performed on fabricated test devices with Cu thin films with SiNx and TiN capping layers. The observations from electromigration experiments on thin Cu metal films at a range of temperatures indicate that the contribution of interface adhesion strength to electromigration resistance decreases with an increase in temperature. The generalized reaction-diffusion theory developed here is modified to develop an expression to account for the effect of base and passivation layer adhesion and temperature on electromigration resistance of metal thin films. The void growth rates measured in the experiments are analyzed with the expression for void growth rate to estimate the interface adhesion strength for the Cu-TiN and Cu-SiNx interfaces. </p> <p><br></p> <p>Demand for increased bandwidth, power efficiency and performance requirements have resulted in a trend of reduction in size and pitch of Cu pillar-Solder micro-bump interconnects used in heterogeneously integrated packages. As the size of micro-bumps reduce, reliability challenges due to voiding in the solder joint and the growth of Cu-Sn intermetallics are observed. The underlying reaction-diffusion mechanisms responsible for Cu-Sn intermetallic growth and voiding in solder joints are unclear at this stage and require further investigation. The current practice of material characterization in micro-bumps involve destructive cross-sectioning and polishing of the micro-bumps after testing. These processes result in loss of continuity in the samples used for the experiments, and material removal due to abrasive polishing might result in a loss of critical information. Therefore, a novel test device capable of non-destructive characterization of Cu-Sn intermetallic growth and voiding in sub-30 micron size micro-bumps is designed and fabricated in this work. The fabricated test devices are subjected to thermal aging for over 1000 h and the underlying reaction-diffusion mechanisms behind the intermetallic phase and void evolution are investigated. </p> <p><br></p> <p>A reaction-diffusion mechanism is proposed explaining the evolution of  various Cu-Sn intermetallic phases and solder joint void observed from experiments. Using the reaction-diffusion mechanism inferred from the thermal aging experiments and the generalized reaction-diffusion theory for phase evolution developed in this thesis, a sharp interface model is developed for the evolution of Cu-Sn intermetallic phases and solder joint void. The diffuse interface phase field equivalent equations for the sharp interface model governing equations are developed using matched formal asymptotic analysis. The evolution of Cu-Sn intermetallic phase and voids in the solder joint are simulated for different temperatures and current density to demonstrate the validity of the phase field and sharp interface models.  </p> <p><br></p>