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Theoretical and computational methods have been used to study nonlinear effects in the mechanical response of materials at the nano and macro scales. These methods include, acoustoelastic theory, molecular dynamics and finite element models. The nonlinear indentation response of Ni thin films of thicknesses in the nano scale was studied using molecular dynamics simulations with embedded atom method (EAM) interatomic potentials. The study included both single crystal films and films containing low angle grain boundaries perpendicular to the film surface. The simulation results for single crystal films show that as film thickness decreases, larger forces are required for similar indentation depths but the contact stress necessary to emit the first dislocation under the indenter is nearly independent of film thickness. The presence of grain boundaries in the films leads to the emission of dislocations at a lower applied stress. For a single crystal Ni thin film of a thickness of 20 nm a direct comparison of simulation and experimental results is presented, showing excellent agreement in hardness values. The effects of using different interatomic potentials and indentation rates for the simulations are also discussed. Dynamic indentation of the Ni thin film was also carried out for different frequencies. It has been found that there is a 12% increase in dislocations compared to quasi static indentation and the results are consistent with experiments. Acoustoelastic theory was used to study how nonlinear elastic properties of unidirectional graphite/epoxy (gr/ep) effect the energy flux deviation due to an applied shear stress. It was found that the quasi-transverse wave (QT) exhibits more flux deviation compared to the quasi-longitudinal (QL) or the pure transverse (PT) due to an applied shear stress. The flux shift in QT wave due to an applied shear stress is higher than that for an applied normal stress along laminate stacking direction for the same magnitude. The QT wave has energy flux deviation due to shear stress at 0o and 90o fiber orientations as compared to normal stress case where the flux deviation is zero. It was found that the energy flux shift of QT wave in gr/ep varies linearly with applied shear stress. The Finite element model of the equations of motion combined with the Newmark method in time was used to confirm the flux shift predicted by theory. / Ph. D.

"Template" and "adder" proteins can be genetically encoded to produce large amyloid fibers when mixed together. Escherichia coli is used to clone a "template" protein, Gd20, which will cooperatively self-assemble with two "adder" proteins, P7Q and P7S, to yield two different large amyloid fibers. Atomic force microscopy (AFM) is used to image the fibers and AFM tip approach/retraction force is used to quantify molecular packing in the fibers. Glutamine (Q)-containing P7Q and serine (S)-containing P7S both have the same hydrophobic core, charge, and hydrogen bonding potential. However, P7Q is highly alpha-helical while P7S contains a beta-sheet core. After 72 hours, the Gd20:P7Q template:adder protein mixture produces tightly packed ~0.3 μm high and ~1.9 μm wide fibers that exhibit a low retraction force of ~44 nN after indentation. The Gd20:P7S mixture produces larger ~1.1 μm high and ~9.7 μm wide fibers exhibiting a much higher retraction force of ~503 nN showing they are much less molecularly packed. These results indicate that the adder protein alpha-helical character is important for self-assembly and molecular packing inside of the large amyloid fiber. The experimental results show that large amyloid fibers with predictable size and mechanical properties can be anticipated and encoded at the genetic level. / Master of Science

The factors controlling the reliability of Pb-free solders when subject to thermomechanical regimes relevant to the harsh aerospace environment have been studied. Ball grid array (BGAs) typical of microelectronic devices have been manufactured in-house and subjected to isothermal ageing and thermal cycling. The BGAs comprised both Cu and Ni-Au metallizations, Pb-free Sn-Ag-Cu 400 and 600μm solder balls, FR4 and Al₂O₃ boards, and included circuits to measure resistance changes due to damage in the joints during thermal cycling. Microstructural evolution within the solders balls and complex interfacial reactions were studied in all configurations using various types of electron microscopy. The mechanical properties of the different phases formed within solder joints were studied using nanoindentation at room and elevated temperatures up to 175°C for the first time. Intermetallic compounds (IMCs) were stiff, hard and brittle with very low creep rates, while the softer primary Sn, eutectic regions and Cu metallization readily underwent creep. Two-dimensional finite element analysis (FEA) of nanoindentation was used to understand better the physical meaning of nanoindentation creep data. Reliability experiments comprised both thermal cycling and FEA of BGAs. The difference in coefficient of thermal expansion (CTE) in the BGA materials caused interfacial fatigue damage in the solder joints, which was detected primarily at the solder/metallization interface of the outermost, most strained solder joint. Accumulated creep strain per cycle at this interface was evaluated using 3D FEA of the stress-strain state of the BGA and results calibrated against experimental BGA mean lifetimes using the Coffin-Mason relationship. Nanoindentation combined with FEA has been shown to be a viable route for the rapid assessment of creep performance and lifetime in lead-free solders under aerospace thermal cycles.

A concepção deste trabalho está ligada ao desenvolvimento de sistemas microeletromecânicos (MEMS) para RF na faixa de frequências de ondas milimétricas. Dentro deste contexto, o Grupo de Novos Materiais e Dispositivos (GNMD) do Laboratório de Microeletrônica (LME) da Escola Politécnica da Universidade de São Paulo (EPUSP) já fabricou RF MEMS que tiveram resultados bastante promissores. No entanto, para obtenção de melhores resultados, é necessária a otimização eletromecânica destes dispositivos e para isso é necessária a extração de suas propriedades mecânicas. Assim, este trabalho teve como objetivo o desenvolvimento de uma metodologia para extração do módulo de elasticidade e tensão residual em MEMS, através da simulação e fabricação de microestruturas específicas para este fim. As técnicas de nanoindentação, frequência de ressonância, raio de curvatura e M-TEST foram estudadas. As microestruturas fabricadas foram cantileveres e pontes feitas de alumínio e cobre. Foram realizadas simulações no software ANSYS para prever as frequências de ressonância e as tensões de pull-in das estruturas antes de serem fabricadas. O módulo de elasticidade do alumínio extraído através da nanoindentação foi de 75,6 ± 4,1 GPa, e o do cobre extraída através da técnica de frequência de ressonância foi de 123 ± 12 GPa. A tensão residual do cobre foi extraída através da técnica de medição do raio de curvatura e foi de -199±105 MPa. O trabalho está vinculado ao projeto Jovem Pesquisador FAPESP (2011/18167-3). / The approach of this work is linked to the development of microelectromechanical systems (MEMS) for RF in the frequency range of millimeter waves. Within this context, the Group of New Materials and Devices (GNMD) of the Laboratory of Microelectronics (LME) of the Polytechnic School of the University of São Paulo (EPUSP) has already manufactured RF MEMS which have had very promising results. However, to obtain better results, it is necessary the electromechanical optimization of these devices through the extraction of their mechanical properties. Thus, this work has the objective of developing a methodology for the extraction of the Young\'s modulus and residual stress in MEMS, through the simulation and fabrication of specific microstructures for this purpose. The techniques of nanoindentation, resonance frequency, radius of curvature and M-TEST were studied. The fabricated microstructures were cantilevers and bridges in aluminum and copper materials. Simulations were performed in the ANSYS software to predict the resonance frequencies and the pull-in voltages of the structures before they were fabricated. The Young\'s modulus of aluminum extracted through nanoindentation was 75,6 ± 4,1 GPa, the resonance frequency of copper extracted by the technique of the same name was 123 ± 12 GPa and the residual stress of copper was extracted through the technique of measuring the radius of curvature and was -199±105 MPa. The work is linked to the project Jovem Pesquisador from FAPESP (2011/18167-3).

A concepção deste trabalho está ligada ao desenvolvimento de sistemas microeletromecânicos (MEMS) para RF na faixa de frequências de ondas milimétricas. Dentro deste contexto, o Grupo de Novos Materiais e Dispositivos (GNMD) do Laboratório de Microeletrônica (LME) da Escola Politécnica da Universidade de São Paulo (EPUSP) já fabricou RF MEMS que tiveram resultados bastante promissores. No entanto, para obtenção de melhores resultados, é necessária a otimização eletromecânica destes dispositivos e para isso é necessária a extração de suas propriedades mecânicas. Assim, este trabalho teve como objetivo o desenvolvimento de uma metodologia para extração do módulo de elasticidade e tensão residual em MEMS, através da simulação e fabricação de microestruturas específicas para este fim. As técnicas de nanoindentação, frequência de ressonância, raio de curvatura e M-TEST foram estudadas. As microestruturas fabricadas foram cantileveres e pontes feitas de alumínio e cobre. Foram realizadas simulações no software ANSYS para prever as frequências de ressonância e as tensões de pull-in das estruturas antes de serem fabricadas. O módulo de elasticidade do alumínio extraído através da nanoindentação foi de 75,6 ± 4,1 GPa, e o do cobre extraída através da técnica de frequência de ressonância foi de 123 ± 12 GPa. A tensão residual do cobre foi extraída através da técnica de medição do raio de curvatura e foi de -199±105 MPa. O trabalho está vinculado ao projeto Jovem Pesquisador FAPESP (2011/18167-3). / The approach of this work is linked to the development of microelectromechanical systems (MEMS) for RF in the frequency range of millimeter waves. Within this context, the Group of New Materials and Devices (GNMD) of the Laboratory of Microelectronics (LME) of the Polytechnic School of the University of São Paulo (EPUSP) has already manufactured RF MEMS which have had very promising results. However, to obtain better results, it is necessary the electromechanical optimization of these devices through the extraction of their mechanical properties. Thus, this work has the objective of developing a methodology for the extraction of the Young\'s modulus and residual stress in MEMS, through the simulation and fabrication of specific microstructures for this purpose. The techniques of nanoindentation, resonance frequency, radius of curvature and M-TEST were studied. The fabricated microstructures were cantilevers and bridges in aluminum and copper materials. Simulations were performed in the ANSYS software to predict the resonance frequencies and the pull-in voltages of the structures before they were fabricated. The Young\'s modulus of aluminum extracted through nanoindentation was 75,6 ± 4,1 GPa, the resonance frequency of copper extracted by the technique of the same name was 123 ± 12 GPa and the residual stress of copper was extracted through the technique of measuring the radius of curvature and was -199±105 MPa. The work is linked to the project Jovem Pesquisador from FAPESP (2011/18167-3).

Made available in DSpace on 2017-07-24T19:22:25Z (GMT). No. of bitstreams: 1 CRISTIAN HIGASHI.pdf: 3013347 bytes, checksum: 87da650524fbc43c80566136e07331cd (MD5) Previous issue date: 2012-12-07 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The aim of this study was to assess the push-out bond strength, nanohardness and Young’s modulus of three resin cements used for luting fiber post. The measurements were taken at cervical (CT), middle (MT) and apical (AT) radicular thirds, at immediate time and after one year of storage in water. Root canals of 57 human teeth were endodontically treated and prepared to cementation of fiber post (White Post DC - FGM) using the cementation systems: Multilink [MUL] (Ivoclar Vivadent), Variolink II + Excite DSC [VAR] (Ivoclar Vivadent) and R RelyXTM Unicem [UNC] (3M ESPE). For the push-out test (n=16), after 24hs of water storage at 37ºC, half the sample (n=8) was transversely sectioned into 6 slices, being 2 slices for each radicular third, which were assess d at 0,5 mm/min. The remaining half (N=8) was kept unsectioned in deionized water at 37ºC for 1 year, followed by sectioning and measuring. For the nanoindentation test, the cemented samples (n=3) were stored in water at 37ºC for 24hs and after were longitudinally sectioned to perform the initial measurements of hardness and elastic’s modulus from cervical to apex. These same samples were stored in deionized water at 37ºC for 1 year and reassessed. The data were analyzed by three-way ANOVA and Tukey’s test (α=0.05). The mean and standard deviation of MUL bond strength (MPa) in AT (19.9 ± 3.9) was higher than MT (15.1 ± 4.7) and CT (14.9 ± 4.2) (p=0.00007). The immediate bond strength of AT (22.0 ± 4.9) decreased significantly after 1 year of water storage (15.1 ±4.1) (p=0.006). The MUL cement obtained higher values of Young’s modulus (GPa) in CT (9.2 ± 1.9) when compared to MT (6.6 ± 2.0) e AT (5.4 ± 2.6)(p=0.01). The AT has the lowest values of hardness (GPa) (0.40 ± 0.10) when compared to MT (0.45 ± 0.12) and CT (0.48 ± 0.11) (p=0.000001). The initial hardness of UNC cement (0.43 ± 0.12) decreased after 1 year of storage in water (0.35 ± 0.14) (p=0.0051). It was concluded that: 1) The bond strength of MUL cement was higher in AT, 2) The AT of the cements suffered higher bond degradation after 1 year of storage water, 3) The Young’s modulus of MUL cement was higher in CT, 4) The AT of all cements had lowest hardness values, 5) After 1 year of storage in water, the UNC cement had a significant decreased of hardness values. / O objetivo deste trabalho foi avaliar a resistência de união, nanodureza e módulo de elasticidade de 3 cimentos resinosos utilizados para cimentar pinos de fibra de vidro. As mensurações foram feitas nos terços cervical [TC], médio [TM] e apical [TA] das raízes, no tempo imediato e após 1 ano de armazenamento em água destilada. Os canais radiculares de 57 dentes humanos unirradiculares foram tratados endodonticamente e preparados para a cimentação dos pinos de fibra de vidro White Post DC (FGM) utilizando os sistemas de cimentação Multilink [MUL] (Ivoclar Vivadent), Variolink II + Excite DSC [VAR] (Ivoclar Vivadent) e RelyXTM Unicem [UNC] (3M ESPE). Para o teste de push-out (n=16), após 24hs de armazenamento em água destilada à 37ºC, metade das amostras (n=8) foram cortadas transversalmente em 6 fatias, sendo 2 fatias para cada terço radicular, que foram testadas à velocidade de 0,5 mm/min. A outra metade das amostras cimentadas (n=8) foram mantidas íntegras em água destilada à 37ºC por 1 ano, seguidos pelos cortes e mensurações. Para o teste de nanoindentação, as amostras cimentadas (n=3) foram armazenadas em água à 37ºC por 24hs e logo após, cortadas longitudinalmente aos seus longos eixos para a realização das mensurações iniciais de nanodureza e módulo de elasticidade do TC até TA. Estas mesmas amostras foram armazenadas em água destilada à 37ºC por 1 ano e retestadas. Os dados foram submetidos a uma análise de variância de três critérios e ao teste de Tukey (α=0,05). A média e desvio padrão dos valores de resistência de união (MPa) do cimento MUL no TA (19,9 ± 3,9) foi maior do que no TM (15,1 ± 4,7) e TC (14,9 ± 4,2) (p=0,00007). A resistência de união imediata do TA (22,0 ± 4,9) diminuiu significativamente após 1 ano de armazenamento em água (15,1 ± 4,1) (p=0,006). O cimento MUL obteve maiores valores de módulo de elasticidade (GPa) no TC (9,2 ± 1,9) em compara ão ao TM (6,6 ± 2,0) e TA (5,4 ± 2,6) (p=0,01). O TA radicular teve os menores valores de nanodureza (GPa)(0,40 ± 0,10) quando comparado com os TM (0,45 ± 0,12) e TC (0,48 ± 0,11) (p=0,000001). A nanodureza inicial do cimento UNC (0,43 ± 0,12) diminui após 1 ano de armazenamento em água (0,35 ± 0,14) (p=0,0051). Concluiuse que: 1) A resistência do cimento MUL foi maior no TA; 2) O TA dos cimentos sofreu uma maior degradação da união após o armazenamento de 1 ano em água; 3) O módulo de elasticidade do cimento MUL foi maior no TC; 4) O TA de todos os cimentos teve menores valores de dureza; 5) O cimento UNC teve uma diminuição significativa dos valores de nanodureza após 1 ano de ar azenamento em água. Palavras-chave: Cimento resinoso. Pino de fibra. Dentina radicular.

L'agence spatiale européenne et le CNES étudient la possibilité d’envoyer des microsystèmes dans l’espace, en particulier pour le gain de masse qu’ils représentent. Afin d’améliorer la fiabilité des composants en couches minces dans le temps et leurs performances, il est nécessaire de connaitre leurs propriétés mécaniques. Plusieurs techniques de caractérisation existent, en particulier la nanoindentation qui sollicite les couches minces directement sur substrat. Mais les résultats peuvent être largement influencés par le substrat dans le cas des couches microniques. Les méthodes de traction uniaxiale (CNES) et du gonflement de membranes autoportantes (INL) permettent de s’affranchir des effets du substrat, mais la fabrication de telles structures est complexe et nécessite bon nombre d’étapes technologiques pour retirer le substrat en face arrière. L’objectif de cette thèse est de comprendre le lien qui existe entre les paramètres de fabrication de couches minces métalliques d'or et d'aluminium, leur microstructure, et leurs propriétés mécaniques à l’aide des outils présentés précédemment. Une perspective étant de mieux agir sur les procédés de fabrication afin d’améliorer la fiabilité des composants. Le premier chapitre présente les différentes techniques de dépôt, leur thermodynamique et cinétique, les types de microstructures rapportées dans la littérature, ainsi que la réalisation des structures de test. Le deuxième présente les caractérisations microstructurales, et la corrélation entre les paramètres de dépôt et les propriétés microstructurales est discutée. Le chapitre trois présente les caractérisations mécaniques des couches minces, sur substrat ou autoportantes, par les méthodes de nanoindentation en pointe Berkovich et sphérique, de microtraction et du gonflement de membrane. Le dernier chapitre est consacré aux relations entre les propriétés microstructurales et mécaniques des couches minces métalliques et à l'influence des traitements thermiques. / The European Space Agency and CNES are studying the possibility of sending microsystems in space, especially for the mass gain they represent. To improve the reliability of components, it is necessary to know their mechanical properties. Several characterization techniques exist, especially nanoindentation of thin films on substrates. However, results can be largely influenced by the substrate in the case of micron layers. The methods of uniaxial tension (CNES) and bulge-test (INL) on freestanding specimen are used to eliminate the effects of the substrate, but the fabrication of such structures is complex and requires many technological steps to remove the substrate on the backside. The objective of this thesis is to understand the relationship between manufacturing parameters of thin metal films of gold and aluminum thin films, their microstructure and mechanical properties using the tools described above. The first chapter presents different deposition techniques, their thermodynamics and kinetics, types of microstructures reported in the literature, and the fabrication of test structures. The second presents the microstructural characterization, and correlation between deposition parameters and the microstructural properties is discussed. Chapter three presents the mechanical characterization of thin films on substrate or freestanding ones, by the methods of nanoindentation with Berkovich and spherical tips, microtensile test and bulge test. The last chapter is devoted to relations between microstructural and mechanical properties of thin metal films and the influence of heat treatments.

Le développement des micro- et nano- technologies est aujourd'hui dépendant de la connaissance du comportement mécanique des couches minces constitutives de ces dispositifs. La caractérisation expérimentale des matériaux est primordiale car les propriétés mécaniques se trouvent, à une telle échelle, fortement dépendantes de l'historique de la couche et de sa microstructure. D'autre part, la mise en œuvre de ces couches minces est multiple. Cette thèse présente une approche transversale, s'articulant autour de techniques de nanoindentation, pour caractériser des couches déposées sur substrat, et de traction uniaxiale applicable à des couches minces autoportantes d'épaisseur submicronique. Elle s'appuie notamment sur un concept de platine de microtraction nomade qui a été amélioré et évalué à l'aide d'une mise en œuvre sur des éprouvettes en aluminium pulvérisé d'épaisseur variant entre 700nm et 1,5µm et des éprouvettes d'or électrolytique de 4µm d'épaisseur.

Dans le domaine de l'électronique de puissance, la gestion thermique de l'intégration des puces en silicium au sein du système global constitue un problème clé. La chaleur dissipée par les composants électriques est évacuée vers l extérieur à travers un drain thermique, généralement en cuivre, qui est brasé sur le substrat céramique. Cette étude est consacrée à l'élaboration de drains thermiques adaptatifs en matériaux composites cuivre allié/fibres de carbone (FC) qui combinent une bonne conductivité thermique et un CTE proche de celui du substrat. Dans ce type de matériau, la liaison interfaciale renfort/matrice doit être forte afin d'optimiser le transfert des propriétés entre les deux composants. Le couple cuivre/carbone étant non réactif, un élément d addition carburigène (Cr ou B) est ajouté à la matrice de cuivre afin de créer cette liaison chimique forte. Un matériau modèle a été réalisé par pulvérisation cathodique afin d étudier la diffusion de l élément d addition au sein de la couche de cuivre vers la zone interfaciale et la formation d un carbure métallique. Une méthode de chimie des solutions a ensuite été utilisée pour élaborer des poudres de cuivre allié de stœchiométrie donnée. Enfin, les matériaux composites (Cu-B/FC et Cu-Cr/FC) ont été élaborés par métallurgie des poudres et leurs propriétés thermiques et mécaniques corrélées à la microstructure et à la chimie des zones interfaciales