L’étude de ce mémoire concerne l’élaboration d'un alliage alternatif sans plomb pour l’électronique de puissance, celui-ci sera utilisé à des fins de brasures. Les brasures actuelles sont composées d’alliages comportant du plombet sont peu résistantes en cas de travail à haute température. Ces systèmes seront progressivement éliminés, ils ne respectent plus la Directive Européenne sur l’environnement (RoHS) et les normes de santé publique en raison de la toxicité du plomb (cancérogène, mutagène, accumulation dans l’environnement …). Le travail a été réalisé avec l’alliage Ag-Sn, l’objectif principal de cette thèse a été d’élaborer le composé Ag3Sn, en raison de sa grande résistance thermique (température de fusion élevée de 480°C). Ses meilleures performances sont avantageuses pour les brasures situées dans des environnements difficiles comme l’aéronautique ou l’automobile. La première partie de ce manuscrit détaille la synthèse du composé Ag3Sn réalisée via la méthode polyol, une voie de chimie douce. Il s’agit d’une technique différente des techniques classiques, comme la voie métallurgique. La synthèse a été réalisée en plusieurs étapes et une méthode d’approches successives a été utilisée afin de déterminer les paramètres de synthèse optimums.Deux protocoles particuliers se détachent et ils permettent d’élaborer des phases résistantes à haute température. Lepremier permet d’élaborer une phase pure d' Ag3Sn, tandis que le second permet d’élaborer deux phases de solutionssolides. Les composés ont été caractérisés par DRX, par imagerie MEB-FEG et MET et par analyse thermogravimétrique.La seconde partie de ce travail est la consolidation de ce composé Ag3Sn par une technique de frittage particulière :le die-bonding, afin de réaliser la connexion entre la puce électronique et un susbtrat de cuivre recouvert d'argent.Une étape de dépôt des poudres sur le substrat a été nécessaire avant de réaliser la consolidation, elle a été réalisée selon différentes techniques : le spin-coating ou le dépôt par sérigraphie. Puis, les paramètres de frittage par die-bonding ont été affinés selon les techniques de dépôt. Enfin, des essais de cisaillement ont été réalisés sur certains échantillons. / The study of this memoir concerns the development of an alternative lead-free alloy for power electronics, which will be used for solders. Nowadays, current solders are composed of alloys containing lead, and aren't resistant at high work temperature. These systems will be phased out, because they no longer comply with the European RoHS Directive and public health standards due to the toxicity of lead (carcinogenic, mutagenic, accumulation in the environment, etc.). This work was carried out with the Ag-Sn alloy, and the main objective was to develop the elaboration of the Ag3Sn compound, due to its high thermal resistance (high melting point of 480°C). Its best performance is an advantage for solders located in difficult work environments such as aeronautics or automobile. First part of this thesis describes the synthesis of Ag3Sn compound with the polyol process, a soft-chemistry routine. It is different from the conventional techniques, like the metallurgical way. Polyol synthesis was realized by following several steps. A method of successive approaches wasdetermine optimum synthesis parameters. Two specific protocols stand out, and they allow the development of high-temperature resistant phases. The first one allows the elaboration of an Ag3Sn pure phase, an the second one allows the development of two compounds of solid solutions. The compounds were characterized by XRD, FEG-SEM, TEM and thermogravimetric analysis. The second part of this work is the consolidation of the Ag3Sn compound with a special sintering technique : the die-bonding, in order to realize the connexion between the electronic chip and the copper substrate coated silver. A first step of depositing powder on the substrate was necessary before carrying out the implementation. It was carried out with various techniques : spin-coating orthe serigraphy deposition. Then, sintering parameters were refined according to the deposition techniques. Finally, shear tests were performed on different samples

<p>Understanding the behavior of materials with nanoscale features is important because of both the  size  of  engineering  devices  and  the  internal  microstructure  of  more  bulk  materials.  Many electronic  components  have  been  miniaturized  in  recent  years  to  attend  the  high  demand  of technology development. Similarly, new stronger bulk metallic materials use nm-scale grain sizes or  precipitates  to  increase  their  strength  over  more  conventionally  processed  alloys.  Nanoscale testing   also   offers   a   route   for   mechanical   behavior   understanding   at   the   microscale. Nanoindentation  has  been  used  to  find  structure-properties  relationships  of  nanostructured materials due to its high load-depth resolution and versatility of the test. Nanoindentation can be used  to  find  hardness  and  modulus  of  the  materials,  important  characteristics  to  evaluate mechanical  performance.  An  introduction  to  strengthening  mechanism  and  generalities  of nanoindentation is shown in Chapter 1.</p> <p>This thesis explores how traditional strengthening mechanisms for bulk materials, can be  applied  to  nanomaterials  and  how  the  microstructure  could  be  tailored  to  achieve  the  desired outcomes on the specific materials studied. The first one is the study of mechanical properties of Nanometallic  Foams  (NMF)  and  its  relationship  with  the  nanostructure.  NMFs  of  pure  copper, CuNi and CuZn alloys were fabricated and tested to find the predominant structural and chemical parameters  of  the  mechanical  properties.  Research  on  how  to  control  and  tailor  the  structural parameters of NMF with viscosity of the precursors is shown in Chapter 2. The relative density was  the  most  predominant  parameter  among  the  structural  parameters  studied.  However,  when relative density parameter is isolated, NMF  are more susceptible to strengthen by second phase precipitation instead of solid solution. The solid solution strengthening mechanism was validated with  MD  simulation  and  agrees  with  the  experimental  findings  that  showed  the  addition  of  Ni atoms to Cu have a moderate effect on the mechanical properties. Chapter 3 presents these findings The  second  example  presented  shows  the  strengthening  effect  of  precipitates  in  nanometallic multilayer. The precipitation was achieved by aging treatment. High temperature nanomechanical testing is also presented in Chapter 4. The third and final example, presented in chapter 5, shows how  the  second  phase  precipitation  and  dispersion  strengthening  of  lead-free  solder  SAC  305 compares  between  samples  aged  for  nine  years  at  body  temperature  and  an  accelerated  aging treatments.</p>

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.

No description available.

This dissertation constitutes two major sections. In the first major section, a kinetic analysis was established to investigate the electromigration (EM), enhanced intermetallic compound (IMC) growth and void formation for Sn-based Pb-free solder joints to Cu under bump metallization (UBM). The model takes into account the interfacial intermetallic reaction, Cu-Sn interdiffusion, and current stressing. A new approach was developed to derive atomic diffusivities and effective charge numbers based on Simulated Annealing (SA) in conjunction with the kinetic model. The finite difference (FD) kinetic model based on this approach accurately predicted the intermetallic compound growth when compared to empirical observation. The ultimate electromigration failure of the solder joints was caused by extensive void formation at the intermetallic interface. The void formation mechanism was analyzed by modeling the vacancy transport under electromigration. The effects of current density and Cu diffusivity in Sn solder were also investigated with the kinetic model. The second major section describes the integration of Step and Flash Imprint Lithography (S-FIL®) into an industry standard Cu/low-k dual damascene process. The yield on a Back End Of the Line (BEOL) test vehicle that contains standard test structures such as via chains with 120 nm vias was established by electrical tests. S-FIL shows promise as a cost effective solution to patterning sub 45 nm features and is capable of simultaneously patterning two levels of interconnect structures, which provides a low cost BEOL process. The critical processing step in the integration is the reactive ion etching (RIE) process that transfers the multilevel patterns to the inter-level dielectrics (ILD). An in-situ, multistep etch process was developed that gives excellent pattern structures in two industry standard Chemical Vapor Deposited (CVD) low-k dielectrics. The etch process showed excellent pattern fidelity and a wide process window. Electrical testing was conducted on the test vehicle to show that this process renders high yield and consistent via resistance. Discussions of the failure behaviors that are characteristic to the use of S-FIL are provided. / text

L'utilisation du diamant comme composant d'électronique de puissance est une perspective intéressante tant en ce qui concerne les applications hautes température que forte puissance. La problématique principale de ces travaux réalisés dans le cadre du programme Diamonix, réside dans l'étude et l'élaboration d'un packaging permettant la mise en oeuvre d'une puce diamant devant fonctionner à des températures variant entre -50°C et 300°C. Nous nous sommes intéressés au choix des matériaux de connexion de la puce avec son environnement. Suite à l'étude bibliographique, nous proposons différentes solutions de matériaux envisageables pour le substrat métallisé, les brasures et les métallisations. Dans un second temps, les différents éléments ont été réalisés puis caractérisés à partir d'essais de nanoindentation et de nanorayage. Des essais mécaniques ont permis de caractériser le comportement élastoviscoplastique et l'endommagement des brasures. Ces derniers essais ont servi de base expérimentale à l'identification des paramètres d'un modèle de comportement viscoplastique couplé avec l'endommagement et qui a été spécialement élaboré pour cette étude. Le modèle de comportement a été implémenté dans un code de calcul par éléments finis via une sous-routine. Il permet notamment de simuler le processus de dégradation d'un assemblage. Enfin, ce modèle de comportement a été mis en oeuvre dans des modélisations thermomécaniques de différentes configurations de véhicules test. / Use of diamond as constitutive component in power electronics devices is an interesting prospect for the high temperature and high power applications. The main challenge of this research work included in the Diamonix program is the study and the elaboration of a single-crystal diamond substrate with electronic quality and its associated packaging. The designed packaging has to resist to temperatures varying between -50°C and 300°C. We contributed to the choice of the connection materials intended to be used in the final test vehicle and which can handle such temperature gaps. In the first part, we present a state-of-the-art of the various materials solutions for extreme temperatures. Following this study, we propose a set of materials which considered as potential candidates for high temperature packaging. Special focus is given for the most critical elements in power electronic assemblies which are metallizations and solders. Once the materials choice carried out, thin substrate metallizations, solders and DBC coatings are studied using nanoindentation and nanoscratch tests. Mechanical tests were also carried out on solders to study their elastoviscoplastic and damage behavior. The experimental results are used as database for the identification of the parameters of the viscoplastic model coupled with a porous damage law, worked out for the case of solders. The behavior model is implemented as a user subroutine UMAT in a FE code to predict the degradation of a 2D power electronic assembly and various materials configuration for a 3D test vehicle.

Lead is a toxic heavy metal that has been extensively used in modern society, causing widespread environmental contamination, even in isolated parts of the world. There is now overwhelming evidence associating lead exposure with wideranging health effects, including reductions in intelligence scores, hyperactivity, shortened concentration spans, poor school performance, violent/aggressive behaviour, hearing loss, delayed onset of puberty, anaemia, and in severe cases, coma and death. In recent years consensus has been reached in respect of the absence of a threshold of safety for key health effects associated with lead exposure, and the permanent and irreversible nature of many of the health and social consequences of exposure to lead. The public health problem of environmental lead exposure has been widely investigated in developed countries such as the United States of America where, since the 1970s, policies and interventions have been followed by significant reductions in blood lead levels amongst children. In developing countries, and in African countries in particular, there is a relative dearth of information on the sources, mechanisms of exposure and blood lead distributions in children, and little action has been taken to protect children against lead poisoning. This study was undertaken to determine the current distribution of blood lead concentrations, and associated risk factors, amongst selected groups of first grade school children in the South African urban settings of Cape Town, Johannesburg 7 and Kimberley, a lead mining town (Aggeneys) and two rural towns in the Northern Cape province. A further objective of the study was to compare blood lead distributions determined in the current study with the findings of similar studies undertaken prior to the introduction in 1996 of unleaded petrol in South Africa. The results show that over the past decade, blood lead concentrations amongst first grade school children have declined considerably, but that large proportions of children, especially those living or attending school in impoverished areas, continue to have intolerably high blood lead concentrations, within a range that puts them at risk of detrimental health and social outcomes. The major sources of exposure to lead in the samples studied were leaded petrol, lead-based paint used to decorate homes and schools, lead solder used in “cottage industries” and other home-based lead-related activities, as well as the transfer of lead particles from lead-related work settings into homes. Recommendations for policy and relevant interventions for the South African context are discussed.

L’introduction des composants grand gap dans le domaine de l’électronique de puissance requiert une optimisation de son environnement (packaging). En effet, les températures auxquelles peuvent être utilisés ce type de composants sont bien souvent plus grandes que celles supportables par le reste du module. De nouvelles techniques d’assemblage sont à l’étude et notamment certaines à base de frittage d’argent. Ces procédés présentent l’avantage de réaliser l’assemblage à une température modérée (similaire à celle d’une brasure), mais toutefois inférieure à celle de fusion de l’argent. La température de fusion du joint d’attache reste celle du matériau massif (plus de 900°C pour l’argent). Cette technique permet donc de réaliser des attaches pouvant fonctionner à très haute température. Ce travail de thèse a porté sur la mise en oeuvre d’une attache de puce par frittage d’argent. Après une étude des paramètres du procédé permettant d’obtenir la meilleure tenue mécanique (cisaillement), nous avons mis en évidence l’effet prépondérant de la finition des pièces à joindre. Lorsque la finition du substrat est de l’argent, aucun problème d’interface n’est observé et les assemblages sont fiables à t0 et en vieillissement. Généralement, la finition standard pour l’électronique de puissance est constituée d’une couche de nickel et d’or. Pour cette finition, le mécanisme semble différent selon l’épaisseur d’or présente sur le substrat ainsi que l’atmosphère utilisée pour le traitement thermique ou encore la charge appliquée. Globalement, plus l’épaisseur d’or est importante, moindre est l’accroche. Ce comportement semble fortement lié à la diffusion extrêmement rapide de l’argent en surface de l’or (et dans l’or). Cette diffusion a pour conséquence la formation d’une couche de solution solide or-argent. Cette couche a pour source de matière les grains d’argent qui permettent l’adhérence du joint d’argent fritté sur le substrat. Lorsque le volume d’or disponible pour la formation de cette couche est grand, la croissance de celle-ci est favorisée (en termes de surface et d’épaisseur). Cette croissance engendre une consommation des « piliers » d’argent et donc un affaiblissement de l’attache. L’application de pression semble augmenter fortement la concentration de piliers et améliore les résultats, tandis que sous azote, la diffusion de l’argent en surface de l’or semble inhibée, permettant l’obtention de bons résultats (à t0 et après cyclage). Ces résultats ont été mis en pratique pour la réalisation de plusieurs prototypes, dont l’un a été testé électriquement et ce de façon fonctionnelle à plus de 300°C. / Use of wide band gap chip in the power electronic industry requires an optimization of the close environment (packaging). Indeed, the can often sustain lower temperature than the die, especially the solder that are used to bond the parts of the module. Consequently, new bonding methods are investigated to enhance the performance of the packages. Silver sintering bonding technique is one the most promising. This method allow to bond parts at moderate temperature and the formed joint to operate at very high temperature (until the melting point of silver). This work is focused on the development of this bonding technique in the case of bonding a dies on a substrate. A study of the influence of the different parameters on the strength of the formed bond has been done. It revealed a major influence of the finishes of the bonded parts. Bonding on silver finished substrate results in good mechanical strength of the bond even after ageing. Furthermore, no interface issues are observed. However, the most used finish for power electronic is not silver but nickel-gold. Regarding this type of finish, the bond quality depends on the gold thickness, sintering profile and also sintering atmosphere. A solid solution of silver and gold seems to develop on the surface of the substrate, decreasing the section of the silver grains in contact with the substrate. Thus the mechanical strength of the assembly is decreased. This effect should be limited by the gold available for the Au-Ag solid solution growth. When sintering under nitrogen, the diffusion of silver on the gold surface is much lower than under air. Good results have been obtained with these configurations and even after ageing. Adding pressure during the thermal treatment seems also to minimize the phenomenon, probably by increasing the number of silver grains in contact with the substrate surface and so reducing the free surface for Au-Ag layer formation. Those results have been used to build prototypes, one of whom has been electrically tested with success at temperatures up to 300°C.

Les nouvelles technologies mécatroniques permettent de réduire fortement la consommation d'énergie et les émissions des véhicules individuels, en introduisant des ruptures indispensables pour une chaîne de traction électrifiée complémentaire ou alternative aux moteurs thermiques. Les assemblages en électronique de puissance utilisés dans les systèmes alterno-démarreurs emploient des alliages de brasure dont il s'agit de trouver des substituants, sans plomb, en accord avec les normes internationales. Cette thèse contribue à la caractérisation métallurgique et mécanique de deux joints brasés sans plomb innovants riches en étain. Ces joints sont produits industriellement par un procédé de brasage laser qui leur confère une microstructure de solidification très hétérogène, peu reproductible, multiphasée et qui présente un grand nombre de défauts. L'objectif de cette thèse est d'apporter une meilleure compréhension à la tenue mécanique de ces joints brasés au cours du vieillissement thermomécanique des assemblages. Les sollicitations thermiques engendrent des contraintes et des déformations plastiques à cause de la dilatation différentielle qui existe entre les différentes couches des matériaux brasés. Des lois de comportement isotropes ont été identifiées à partir d'une base expérimentale d'essais de traction sur des matériaux massifs. Ces lois, utilisées dans des simulations aux éléments finis, ont permis d'évaluer l'effet négatif du défaut de porosité inhérent au procédé de brasage. Des essais de vieillissement couplés à des observations de l'évolution de la microstructure ont permis de montrer l'influence de l'orientation des grains d'étain sur l'amorçage de fissure. Nous n'avons pas pu proposer de volume élémentaire représentatif du fait de la complexité de la structure. Une méthode inverse a été mise en oeuvre en parallèle de la conception d'un banc d'essai de flexion in-situ sous profilomètre afin de placer les premières briques permettant la caractérisation mécanique de joints brasés industriels. / The new mechatronic technologies can significantly reduce the energy consumption and gas emissions of personal cars, by introducing rupture innovations in electrified powertrains complementarily or alternatively to combustion engines. The power electronics assemblies used in starter-alternator systems use solder joints which need to be substituted with lead-free solder in agreements with international standards. This thesis contributes to the metallurgical and mechanical characterization of two tin-based lead-free solder joints. These joints are produced industrially with a Die Laser Soldering process which leads to heterogeneous solidification microstructures, poorly reproducible, multiphased, and with defects. The objective of this thesis is to provide a better understanding of the solder joints lifetime during thermomechanical aging. Thermal aging generates stresses and plastic deformation due to the mismatch in the coefficients of thermal expansion between the different layers of the assemblies. Isotropic constitutive laws were identified from an experimental database of tensile tests on bulk specimens. Those constitutive laws were used in finite element simulations in order to assess the negative effect of the solder joint porosity, inherent flaw traced back to the soldering process. Aging tests coupled with observations of the microstructure evolution have shown the influence of tin grains orientation on crack initiation. The heterogeneity of the microstructure prevents us from proposing a representative volume element of the materials. An inverse method has been implemented in parallel with the development of an in situ bending test bench under a profilometer in order to build the first steps for the mechanical characterization of industrial solder joints.

The artist discusses her Master of Fine Arts exhibition at East Tennessee State University, Slocumb Galleries, Johnson City, Tennessee, October 28-November 8, 2002. Her exhibition was a personal narrative of her southern upbringing in small town Appalachia as well as a reflection of her inner thoughts and feelings towards feminism, adolescence, sexuality and Barbie. She chose to reference the female form, void of an actual body, implied through clothing. Works are figurative and sculptural and are constructed of copper, sterling and fine silver. They are sculptural hollow vessels, raised, formed, and colored with gesso and prismacolor pencils. Topics discussed: the artist's experiences as a woman, development in graduate school, casting versus raising, a detailed technical discussion on each piece, the influences of Marilyn da Silva’s use of the narrative and color on metal, and Judith Shea’s use of clothing to reference the human form. Includes images and discussions of twenty-six works and images of the exhibition.