The problem of inadequate measurement techniques for quantifying the isothermal solidification process during transient liquid phase sintering (TLPS) in binary isomorphous systems such as Ni-Cu, and the resulting uncertainty regarding the solidification mechanism and its sensitivity to important process parameters, has been investigated. A unique combination of differential scanning calorimetry (DSC), neutron diffraction (ND), and metallographic techniques has enabled the quantitative characterization of important TLPS stages (i.e., solid-state sintering, melting and dissolution, isothermal solidification, and homogenization) as well as verifying the re-melt behaviour of post-sintered specimens and measuring variable melting point (VMP) properties. This has resulted in the advancement of the fundamental understanding of liquid formation and its removal mechanism during isothermal, or diffusional, solidification. The Ni-Cu system was chosen for experimentation due to its commercial relevance as a braze filler material and also because it is an ideal model system (due to its isomorphous character) that is not well understood on a quantitative or phenomenological basis. Samples consisted of elemental Ni and Cu powder mixtures of varying particle size and composition. In DSC experiments, the progress of isothermal solidification was determined by measuring the enthalpy of melting and solidification after isothermal hold periods of varying length and comparing these to the measured enthalpy of pure Cu. The low melting enthalpies measured for all Ni/Cu mixtures heated just past the Cu melting point (1090°C) indicate that solid-state sintering and interdiffusion during heat-up significantly suppress initial liquid formation and densification from the wetting liquid. For samples heated well past the Cu melting point (1140°C), Ni dissolution causes increased initial liquid fractions and densification. It was found that significantly more time was required for complete liquid removal at 1140°C vs. 1090°C. This is attributed to the observed increase in initial liquid fractions formed at higher processing temperatures due to the dissolution of Ni. This effectively counteracts the increased diffusivities at these temperatures, and thus more time is required to completely remove the increased liquid content. TLP mixtures sintered at 1140°C using three different particle sizes revealed that fine base metal Ni particles cause high degrees of solid-state interdiffusion during heat-up, small initial liquid fractions, and accelerated liquid removal rates due to high surface area/volume ratios. A diffusion-based analytical model was developed to account for these effects (i.e., particle size, temperature, solid-state sintering, and dissolution). Comparison with experimental DSC results reveals that this model can accurately predict liquid removal given accurate diffusivities. Metallographic analysis of post-sintered DSC specimens via SEM and EDS indicates that isothermal liquid solidification leaves behind Ni-rich cores surrounded by Cu-rich matrix regions having compositions given by the Ni-Cu phase diagram solidus (CS) at a selected isothermal processing temperature (TP). ND experiments were used to investigate the melting event and interdiffusion during the isothermal hold segment by analyzing the evolution of the {200} FCC peaks of Ni and Cu. ND patterns were collected in situ at 1 minute intervals during prolonged sintering cycles for larger powder specimens. The Cu melting event was characterized by an abrupt decrease in Cu peak intensity at 1085°C as well as a shift towards higher 2 angles corresponding to lower Cu contents. This shifted residual peak (hereafter referred to as the CS peak) originates from regions of the specimen having compositions near solidus at TP. Immediately following the melting event, the evolution of ND patterns shows that these CS peaks grow rapidly, indicating the isothermal growth of a Cu-rich phase. These in situ findings confirmed the metallographic and DSC data and indicated that isothermal solidification of the liquid phase proceeds via the growth of a solute-rich solid solution layer surrounding the Ni particles. This occurs by the transient progression of the solid/liquid interface at compositions given by the liquidus and solidus (CS/CL). During sintering, diffraction intensities gradually increased at intermediate 2 angles between previous Ni and Cu peaks. ND patterns gradually evolved from initially having a broad double-peak profile to a sharper single-peak profile due to increased Ni-Cu interdiffusion. The 2position and width of the post-sintered peaks indicated very homogeneous sintered alloys. Metallographic analysis of post-sintered specimens having undergone prolonged sintering and homogenization revealed extensive Kirkendall pore formation from unequal diffusivities (DCu > DNi). In this study, the unique combination of diffusion-based modelling as well as DSC, ND, and supporting metallographic analysis has enabled the identification of characteristic sintering behaviour, important process parameters, and processing windows for TLPS in Ni-Cu systems. Quantitative and in situ information of this nature is absent in the previous TLPS literature.

The problem of inadequate measurement techniques for quantifying the isothermal solidification process during transient liquid phase sintering (TLPS) in binary isomorphous systems such as Ni-Cu, and the resulting uncertainty regarding the solidification mechanism and its sensitivity to important process parameters, has been investigated. A unique combination of differential scanning calorimetry (DSC), neutron diffraction (ND), and metallographic techniques has enabled the quantitative characterization of important TLPS stages (i.e., solid-state sintering, melting and dissolution, isothermal solidification, and homogenization) as well as verifying the re-melt behaviour of post-sintered specimens and measuring variable melting point (VMP) properties. This has resulted in the advancement of the fundamental understanding of liquid formation and its removal mechanism during isothermal, or diffusional, solidification. The Ni-Cu system was chosen for experimentation due to its commercial relevance as a braze filler material and also because it is an ideal model system (due to its isomorphous character) that is not well understood on a quantitative or phenomenological basis. Samples consisted of elemental Ni and Cu powder mixtures of varying particle size and composition. In DSC experiments, the progress of isothermal solidification was determined by measuring the enthalpy of melting and solidification after isothermal hold periods of varying length and comparing these to the measured enthalpy of pure Cu. The low melting enthalpies measured for all Ni/Cu mixtures heated just past the Cu melting point (1090°C) indicate that solid-state sintering and interdiffusion during heat-up significantly suppress initial liquid formation and densification from the wetting liquid. For samples heated well past the Cu melting point (1140°C), Ni dissolution causes increased initial liquid fractions and densification. It was found that significantly more time was required for complete liquid removal at 1140°C vs. 1090°C. This is attributed to the observed increase in initial liquid fractions formed at higher processing temperatures due to the dissolution of Ni. This effectively counteracts the increased diffusivities at these temperatures, and thus more time is required to completely remove the increased liquid content. TLP mixtures sintered at 1140°C using three different particle sizes revealed that fine base metal Ni particles cause high degrees of solid-state interdiffusion during heat-up, small initial liquid fractions, and accelerated liquid removal rates due to high surface area/volume ratios. A diffusion-based analytical model was developed to account for these effects (i.e., particle size, temperature, solid-state sintering, and dissolution). Comparison with experimental DSC results reveals that this model can accurately predict liquid removal given accurate diffusivities. Metallographic analysis of post-sintered DSC specimens via SEM and EDS indicates that isothermal liquid solidification leaves behind Ni-rich cores surrounded by Cu-rich matrix regions having compositions given by the Ni-Cu phase diagram solidus (CS) at a selected isothermal processing temperature (TP). ND experiments were used to investigate the melting event and interdiffusion during the isothermal hold segment by analyzing the evolution of the {200} FCC peaks of Ni and Cu. ND patterns were collected in situ at 1 minute intervals during prolonged sintering cycles for larger powder specimens. The Cu melting event was characterized by an abrupt decrease in Cu peak intensity at 1085°C as well as a shift towards higher 2 angles corresponding to lower Cu contents. This shifted residual peak (hereafter referred to as the CS peak) originates from regions of the specimen having compositions near solidus at TP. Immediately following the melting event, the evolution of ND patterns shows that these CS peaks grow rapidly, indicating the isothermal growth of a Cu-rich phase. These in situ findings confirmed the metallographic and DSC data and indicated that isothermal solidification of the liquid phase proceeds via the growth of a solute-rich solid solution layer surrounding the Ni particles. This occurs by the transient progression of the solid/liquid interface at compositions given by the liquidus and solidus (CS/CL). During sintering, diffraction intensities gradually increased at intermediate 2 angles between previous Ni and Cu peaks. ND patterns gradually evolved from initially having a broad double-peak profile to a sharper single-peak profile due to increased Ni-Cu interdiffusion. The 2position and width of the post-sintered peaks indicated very homogeneous sintered alloys. Metallographic analysis of post-sintered specimens having undergone prolonged sintering and homogenization revealed extensive Kirkendall pore formation from unequal diffusivities (DCu > DNi). In this study, the unique combination of diffusion-based modelling as well as DSC, ND, and supporting metallographic analysis has enabled the identification of characteristic sintering behaviour, important process parameters, and processing windows for TLPS in Ni-Cu systems. Quantitative and in situ information of this nature is absent in the previous TLPS literature.

Ice structuring proteins (ISPs) naturally exist in many foods consumed as part of the human diet including plants or fish. ISPs from winter wheat grass have gained interest in the pharmaceutical and food industries as a non-toxic, natural and cost-effective product, which is easy to prepare as a crude extract. However, they have not been purified reproducibly and studied in detail to elucidate their structures, mechanism of actions and difference(s). ISPs from the apoplast region of cold acclimated winter wheat leaves were extracted through vacuum infiltration and purified using heat and ethanol precipitations, size exclusion and anionic exchange fast protein liquid chromatography techniques. The ISPs showed both significant inhibition of ice growth and thermal hysteresis activities. The non-acclimated apoplastic extracts from winter wheat leaves contained similar proteins without any abovementioned activities. The ISPs contained disulfide bridges, similar to thaumatin-like proteins (TLPs) and partially similar to ISPs from winter rye leaves and carrot. ISPs remained active after thermal treatment (i.e., pasteurization conditions) and over a wide range of pH (3-12). There are very few quantitative assays to measure the activity of antifreeze proteins (AFPs, or Ice Structuring Proteins, ISPs), which often suffer from various inaccuracies and inconsistencies. Some methods rely only on unassisted visual assessment. When microscopy is used to measure ice crystal size, it is critical that standardized procedures be adopted, especially when image analysis software is used to quantify sizes. Differential Scanning Calorimetry (DSC) has been used to measure the thermal hysteresis activity (TH) of AFPs. In this study, DSC was used isothermally to measure enthalpic changes associated with structural rearrangements as a function of time. Differences in slopes of thermograms between winter wheat ISP or AFP type I containing samples, and those without ISP or AFP type I were demonstrated. ISP or AFP type I containing samples had much higher slopes compared to those without ISP or AFP type I. Samples with higher concentration of ISP or AFP type I showed higher slope values. The proteinaceous activity of ISPs or AFP type I was confirmed by demonstrating changes in samples with and without proteases. A proposed mechanism of this method is discussed.

L'assemblage tridimensionnel des circuits microélectroniques et leur utilisation dansdes conditions environnementales extrêmement sévères nécessitent ledéveloppement d’alternatives plus robustes pour les contacts électriques. Unetechnique prometteuse est la transformation des contacts de brasure conventionnelleen composés intermétalliques (IMC). Ce processus est appelé « Transient LiquidPhase Soldering » (TLPS).Dans ce contexte, des tests accélérés permettant la formation d’IMC parélectromigration et thermomigration ont été effectués sur des structures « Packageon Package ». L'objectif principal est le développement d'un modèle généralpermettant de décrire la formation des IMC dans les joints de brasure. Combiné avecune analyse par éléments finis ce modèle pourra être utilisé pour prédire la formationdes IMC dans les joints de brasure pour des structures et des profils de missiondifférents. Le modèle de formation des IMC pourra être utilisé pour optimiser unprocessus TLPS. / A further miniaturization of microelectronic components by three dimensionalpackaging, as well as the use of microelectronic devices under harsh environmentconditions, requires the development of more robust alternatives to the existing Snbased solder joints. One promising technique is the diffusion and migration driventransformation of conventional solder bumps into intermetallic compound (IMC)connections. The related process is called transient liquid phase soldering (TLPS).Against this background an investigation of the IMC formation under consideration ofelectromigration and thermomigration was performed. For the stress tests Packageon Package structures are used. The final result is a general model for the IMCformation in solder joints. Combined with a Finite Element Analysis (FEA) this modelis used to predict the IMC formation in solder joints for a broad range of boundaryconditions. In future the model of the IMC formation can be used to optimize a TLPSprocess.

The present masters's thesis informs about the development and application of low-temperature sintering pastes in the manufacture and assembly of PCB components of the enclosing lead-free using nanoparticles of metals and their compounds. Lead-free brazing technology which s using in the present time, which has its drawbacks, however, and thus gaining other appropriate alternatives that seek to replace or further refined lead brazing. The introduction of the theoretical part inform about retrieval method of the type, composition and properties of low-temperature sintering pastes consisting of metal nanoparticles and their compounds. This section describes and explains the reaction mechanisms taking place during the sintering process. The end of the first chapter is dedicated to nanotechnology and production of nanoparticles and their compounds for the needs of the low-temperature sintering and possible related problems. Folowing section is devoted to examples of practitioners of the application and use of low-temperature sintering pastes and tests with which to assess the characteristics and quality of the related sintering conection. At the end of the thesis is a summary perspective and the use of low-temperature sintering technology nanoparticle past into the future. The experimental part is devoted to the application of conductive ink on the base of graphite for the production of 1V, 2V and 4V structures and their electroplated by the copper. There were created technological processes of 2V and 4V structures and test proposed methodologies resistance conductive theme to environmental influences. Filling pasta was tested in implementing 4V structure. There were made microsections various technological applications and their results were processed and evaluated.

<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>