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2.
The current aqueous cleaning step in the surface preparation of aluminum nitride (AlN) prior to metallization causes performance and reliability issues for the substrates used for microelectronic packaging due to surface reactions. These issues limit the use of AlN and its replacing of BeO, an environmentally hazardous material currently used. The aim of this investigation was to determine the effects of different solutions on the surface of AlN substrates under varying conditions at times up to 2419.2 ks (28 days). Concentration of the solutions, temperature, and immersion time were varied for the AlN samples in the solutions. Both elevated temperatures (50°C and 90°C) and low temperatures (5°C) were investigated.
Four general types of behavior were observed: minor changes in average surface roughness and microstructure, linear change in average surface roughness and pitted grains, nonlinear change in average surface roughness and product formation on AlN surface, and miscellaneous change in average surface roughness with surface product formation.
The surface roughening kinetics were very complex due to changes in both the reaction product morphology and reaction mechanism with temperature, solvent, and pH for a specific solvent. Minor changes in average surface roughness and microstructure were observed for HCl pH = 5, H2 SO4 pH = 5, NaOH pH = 8, NaOH pH = 10, NaOH pH = 12, deionized water and Alfred tap water at 5°C, HCl pH = 3 and oleic acid at 50°C and citric acid and oleic acid at 90°C. Linear changes in average surface roughness and pitted grains were observed for HCl pH = 2 and H2SO4 pH = 3 at 50°C and HCl pH = 2, H2SO4 pH = 3, and deionized water at 90°C. Non-linear change in average surface roughness and product formation on AlN surface was observed for HCl pH = 5, NaOH pH = 8 and Alfred tap water at 50°C and HCl pH = 5 and H2SO4 pH = 2 at 90°C. Miscellaneous changes in average surface roughness with surface product formation were observed for H2SO4 pH = 2, H2SO4 pH = 5, NaOH pH = 10, NaOH pH = 12, citric acid, Micro-90 and deionized water at 50°C and HCl pH = 3, H2SO4 pH = 5, NaOH pH = 8, NaOH pH = 10, NaOH pH = 12, Micro-90 and Alfred tap water at 90°C. 相似文献
Four general types of behavior were observed: minor changes in average surface roughness and microstructure, linear change in average surface roughness and pitted grains, nonlinear change in average surface roughness and product formation on AlN surface, and miscellaneous change in average surface roughness with surface product formation.
The surface roughening kinetics were very complex due to changes in both the reaction product morphology and reaction mechanism with temperature, solvent, and pH for a specific solvent. Minor changes in average surface roughness and microstructure were observed for HCl pH = 5, H2 SO4 pH = 5, NaOH pH = 8, NaOH pH = 10, NaOH pH = 12, deionized water and Alfred tap water at 5°C, HCl pH = 3 and oleic acid at 50°C and citric acid and oleic acid at 90°C. Linear changes in average surface roughness and pitted grains were observed for HCl pH = 2 and H2SO4 pH = 3 at 50°C and HCl pH = 2, H2SO4 pH = 3, and deionized water at 90°C. Non-linear change in average surface roughness and product formation on AlN surface was observed for HCl pH = 5, NaOH pH = 8 and Alfred tap water at 50°C and HCl pH = 5 and H2SO4 pH = 2 at 90°C. Miscellaneous changes in average surface roughness with surface product formation were observed for H2SO4 pH = 2, H2SO4 pH = 5, NaOH pH = 10, NaOH pH = 12, citric acid, Micro-90 and deionized water at 50°C and HCl pH = 3, H2SO4 pH = 5, NaOH pH = 8, NaOH pH = 10, NaOH pH = 12, Micro-90 and Alfred tap water at 90°C. 相似文献
3.
The effect of brittle failures on the elastic wave propagation along cylindrical bars is analysed. From experimental observations provided by spalling tests of ceramic materials, a theoretical analysis is carried out based on a finite elements simulation of the experiments and a mathematical analysis of the pulses by means of Fourier Transform techniques. Differences between the propagating waves before and after the material failure are revealed. After failure, the pulse is influenced by dispersion effects and its shape changes during propagation. To correct this effect, a procedure based on Bancroft's curves is suggested. Finally, some clues about the way to get consistent results from spalling tests are given. 相似文献
4.
B. Erzar P. Forquin 《Mechanics of materials : an international journal》2011,43(9):505-527
Due to their large aggregates size and their heterogeneous microstructure, concretes are difficult materials to test at high strain-rates. Direct tensile tests, spalling tests and edge-on impact experiments have been especially developed and performed on a standard concrete (max grain size of 8 mm). The influence of free water on the high strain rate behaviour has been carefully evaluated. Numerical simulations of dynamic testing have been also performed using a mesoscopic approach in which the matrix and the aggregates are differentiated. Numerical and analytical homogenization methods have been employed to define a model-concrete which fits experimental data of simple and œdometric compression tests. Then, the numerical simulations with several random distributions of aggregates were conducted to validate the processing methods applied to the experimental data of the dynamic tests. Moreover an anisotropic damage model coupled to the mesoscopic approach has been used to simulate the dynamic behaviour of concrete under impact. It allows predicting the increase of strength and cracking density with strain-rate and the free water influence on the dynamic behaviour of concrete. 相似文献
5.
《岩石力学与岩土工程学报(英文版)》2022,14(6):1722-1736
Large shear deformation problems are frequently encountered in geotechnical engineering. To expose the shear failure mechanism of rock tunnels, compression-shear tests for rock models with circular tunnel were carried out, including single tunnel and adjacent double tunnels. The failure process is recorded by the external video and miniature cameras around the tunnel, accompanied by real-time acoustic emission monitoring. The experiments indicate that the shearing processes of rock tunnel can be divided into four steps: (i) cracks appeared around tunnels, (ii) shear cracks and spalling ejection developed, (iii) floor warping occurred, and (iv) shear cracks ran through the tunnel model. Besides, the roughness of the sheared fracture surface decreased with the increase in normal stress. Corresponding numerical simulation indicates that there are tensile stress concentrations and compressive stress concentrations around the tunnel during the shearing process, while the compressive stress concentration areas are under high risk of failure and the existence of adjacent tunnels will increase the degree of stress concentration. 相似文献
6.
In der jüngeren Vergangenheit hat sich gezeigt, dass Straßen tunnel durch größere Brände in erheblichem Umfang geschädigt werden können. In der Folge wurden verschiedene internationale Forschungsprojekte durchgeführt, um den baulichen Brandschutz von Straßentunneln weiterzuentwickeln. Aufbauend auf den internationalen Forschungsprojekten wurden vom BMVBS und der BASt drei nationale Forschungsprojekte zum baulichen Brandschutz von Straßentunneln initiiert. In diesen Projekten wurden vorhandene Temperatur‐Zeit‐Verläufe (sog. “Brandkurven”) für Straßentunnel, Brandver suche in Tunneln und reale Brände in Straßentunneln im Hinblick auf eine mögliche Anwendung zur Bemessung des baulichen Brandschutzes von Straßentunneln analysiert. Außerdem wurden die Temperatureindringung in die Tunnelinnenschale und die Tragfähigkeit von üblichen Tunnelquerschnitten infolge Brandeinwirkung numerisch ermittelt. Schließlich wurde anhand von Brandversuchen an großmaßstäblichen Probekörpern die Wirkung von PP‐Faserbeton auf das Abplatzverhalten von Innenschalenbeton untersucht. Über das Vorgehen und die Ergebnisse dieser Forschungsprojekte wird im Folgenden berichtet. Latest developments for structural fire protection of road tunnels. In the recent past it was shown that road tunnels can be damaged severely by large fires. For that reason several international research projects were carried out for further development of structural fire protection of road tunnels. Based on international research projects three national research projects were initiated by the Federal Ministry of Transport, Building and Urban Development (BMVBS) and the Federal Highway Research Institute (BASt). In the course of these projects existing temperature‐time‐progressions (so called ”fire curves”) for road tunnels, fire tests in tunnels and real fires in road tunnels were analyzed with regard to a possible application for the design of structural fire protection of road tunnels. Furthermore the temperature penetration in the tunnel lining and the load bearing capacity of usual tunnel sections were numerically examined under fire influence. Finally the influence of fiber‐modified concrete on the effect of explosive spalling was investigated by means of large scale fire tests on specimens made of concrete for tunnel lining. In the following procedures and results of the national research projects are described. 相似文献
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8.
ABSTRACT A two-dimensional finite element model is developed for kiln-drying of refractory concrete. Using this model simulations are carried out for refractory concrete castings of different thicknesses to investigate the effects of drying schedules on pore steam pressure and moisture removal. Simulation results from both one- and two-dimensional models are compared and discussed. On the basis of the simulation results new realistic drying schedules are suggested. 相似文献
9.
Pore pressure development in hybrid fibre-reinforced high strength concrete at elevated temperatures
The present experimental work investigates the build-up of pore pressure at different depths of High Strength Concrete (HSC) and Hybrid-Fibre-Reinforced High Strength Concrete (HFRHSC) when exposed to different heating rates. First, the effect of the measurement technique on maximum pore pressures measured was evaluated. The pressure measurement technique which utilised a sintered metal and silicon oil was found to be the most effective technique for pore pressure measurement. Pore pressure measurements carried out showed that addition of polypropylene fibres is very effective in mitigation of spalling and build-up of pore pressure inside heated HSC. Addition of steel fibres plays some role in pore pressure reduction at relatively higher pressures in deeper regions of concrete during fast heating. Pore pressure development is highly influenced by the rate of heating with fast heating leading to higher pore pressures in the deeper regions of concrete compared to slow heating. 相似文献
10.
在深部高地应力硬岩开采过程中,经常可以观测到与开挖面基本平行的板裂破坏,这种破坏形式不同于剪切破坏,目前已引起国内外学者的广泛关注。通过工程现场高地应力硬岩板裂破坏的实例分析,观察到硬岩的板裂、片帮、V形槽、岩芯饼化等张性破坏特征,并对高应力硬岩的理论和试验研究现状进行了论述,给出了目前高应力硬岩板裂破坏的工程判据曲线,最后对硬岩板裂破坏的进一步研究工作进行了展望。 相似文献