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71.
Rolf Johannessen Frøydis Oldervoll Frode Strisland 《Microelectronics Reliability》2008,48(10):1711-1719
Reliable interconnects are essential for microelectronic systems intended for long life times in harsh environment applications. Intermetallic growth accelerates as the temperature increases, and the material system must be carefully selected to avoid mechanically and/or electrically weak connections. The dominating chip metallization is aluminium, and aluminium wire-bonding is therefore recommended to obtain a mono-metallic system at chip level. A suitable substrate metallization compatible with aluminium wire-bonds at high temperatures (HT) should therefore be found.Test substrates with low temperature co-fired ceramic (LTCC) silver conductors plated with nickel/gold, gold and aluminium thin film, gold thick film, and silver thick film plated with copper/nickel/gold have been manufactured. Wedge/wedge aluminium wire-bonding were performed with 25 μm aluminium wire on the substrates before they were subjected to long term ageing at temperatures up to 250 °C for 6-12 months. Bond-pull strength and electrical resistance were measured during ageing on selected components.The present work shows that long term reliable aluminium wire-bonds for 250 °C operation is feasible both with thin film, thick film and LTCC substrate technology. For the screen-printed conductors, a plating system with nickel is necessary. Aluminium wire bonded to gold thin film displays reliable long term high temperature performance for gold thicknesses up to ∼1 μm. 相似文献
72.
Frode?S?rmoEmail author J?rg?Cassens Agnar?Aamodt 《Artificial Intelligence Review》2005,24(2):109-143
We present an overview of different theories of explanation from the philosophy and cognitive science communities. Based on
these theories, as well as models of explanation from the knowledge-based systems area, we present a framework for explanation
in case-based reasoning (CBR) based on explanation goals. We propose ways that the goals of the user and system designer should
be taken into account when deciding what is a good explanation for a given CBR system. Some general types of goals relevant
to many CBR systems are identified, and used to survey existing methods of explanation in CBR. Finally, we identify some future
challenges. 相似文献
73.
A neutralization experiment comparing NaOH, limestone slurry and finegrained limestone was performed using smolts of Atlantic salmon as testfish. Smolts were raised on chronically acid Lake Liervatn (pH = 4.9–5.4, conductivity = 55 μ S cm−1, Ca = 1.3 mg l−1, labile Al = 40 μg l−1). As a result testfish were sublethally stressed prior to the experiment, as indicated by low levels of plasma chloride. During the experiment, smolts were held in keepnets in the middle of large plastic enclosures without sediment contact. Rapid changes in pH and Al-speciation were recorded after addition of the neutralizing agents. No mortality of fish occurred during the 3 days exposure. Plasma chloride levels in fish exposed to limestone slurry, limestone and the lowest concentration of NaOH (pH = 5.9) did not differ significantly from levels in fish from the reference group. Fish exposed to the highest concentration of NaOH (pH > 7.45), however, experienced a significant decrease in plasma chloride levels. Increased sublethal stress in treatments with NaOH was presumably caused by the presence of aluminate ions [Al(OH)4−] at high pH and by low concentrations of Ca. The importance of maintaining pH below 7 when using bases with monovalent cations is emphasized. Adding inorganic aluminium to the lake water induced loss of plasma chloride within 48 h at 70 μg labile Al l−1 at pH 5.1 and 1.2 mgCa l−1. 相似文献
74.
Jianglong Pu Yi Luo Ningning Wang Hongxia Bao Xiuhui Wang Eika W. Qian 《International Journal of Hydrogen Energy》2018,43(6):3142-3153
A series of Ni@Al2O3 core-shell catalysts with ceria added to the surface of Ni nanoparticles or inside the alumina shell were prepared, and the effect of ceria addition on the performance of the catalyst in the steam reforming of acetic acid was investigated. The prepared catalysts were characterized by BET, XRD, HRTEM, H2-TPR and DTG. The addition of ceria to the surface of nickel nanoparticles greatly enhanced the activity of catalyst owing to the presence of the mobile oxygen, which migrated from the ceria lattice. Among the prepared catalysts, the Ni@Al10Ce catalyst showed the highest activity with a conversion of acetic acid up to 97.0% even at a low temperature (650 °C). The molar ratio of CO2/CO was also improved due to the oxidation of CO by the mobile oxygen into CO2. The coke formation on the core-shell catalysts was significantly inhibited by the addition of ceria to the surface of nickel nanoparticles due to the oxidation of carbon species by the mobile oxygen in the ceria lattice. However, the Ni@Al10Ce-a catalyst with ceria added to the alumina shell showed a low activity and the formation of a large amount of coke. It is suggested that only the ceria in close to the Ni surface has the promoting effect on the catalytic performance of the Ni@Al2O3 catalyst in the steam reforming of acetic acid. 相似文献