Encapsulation of naked dies for bulk silicon etching with TMAH

Because of the increasing number of metal levels within a semiconductor device and the ongoing transition to new package types failure analysis from the back side of a die becomes necessary. A useful chemical for bulk silicon removal is tetra-methyl-ammonium-hydroxide (TMAH). Because of the aggressive etch conditions, the edges of naked dies have to be protected against destruction by encapsulation into an appropriate molding compound. Different encapsulation materials were evaluated to identify a useful molding compound and an encapsulation method for bulk silicon removal of naked dies using TMAH. Problems as well as results are described in this paper.     

Eye Movements and Behavioral Responses to Threatening and Nonthreatening Stimuli During Visual Search in Phobic and Nonphobic Subjects.

Spider-phobic and nonphobic subjects searched for a feared/fear-relevant (spider) or neutral target (mushroom) presented in visual matrices of neutral objects (flowers). In half of the displays, the mushroom target was paired with a spider distractor, or a spider target was paired with a mushroom distractor. Although all subjects responded faster to the neutral target than to the feared/fear-relevant target, phobics were slower to respond than nonphobics when a mushroom target was presented with a spider distractor. Their eyes appeared to be drawn to the feared distractor before fixating neutral targets. A further experiment indicated no group differences when subjects merely judged the homogeneity of matrices. Thus, threat seems to capture the attention of phobics only when it is part of a background that subjects are explicitly instructed to ignore. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hochdruckflüssigchromatographische Untersuchung von Zimt-CO2-Hochdruckextrakten im Vergleich mit Zimtölen

Nowadays supercritical CO₂ extracts of cinnamon and cassia are coming more and more in trade. Contrary to cinnamon and cassia oils there are very few references in literature about these. Commercially available supercritical CO₂ extracts of cinnamon and cassia barks (cinnamon type Ceylon and type Madagascar, cassia type China and type Indonesia) were analysed by HPLC and compared with cinnamon and cassia oils. The results of the analysis showed that the main compounds evidently differed depending on the species of cinnamon (Cinnamomum zeylanicum, C. cassia andC. burmanii) and on the kind of sample, whereby there was a great difference not only between oils and CO₂ extracts, but also between so-called ?selective extracts“ (40°C/90 bar) and ?total extracts“ (40°/280–300 bar).     

Microprocesses of metal dusting on nickel and Ni-base alloys

Microstructural and microchemical investigations were carried out on nickel and Inconel 600 after exposure to strongly carburizing atmospheres at temperatures of about 600 to 650°C to study their metal dusting behaviour. Contrary to iron and low-alloy steels, where metal dusting proceeds via the formation and disintegration of a metastable carbide M₃C, both nickel and Inconel 600 directly disintegrate. Inside the metal this disintegration proceeds by formation of thin graphite filaments of nearly 10 nm in diameter, the atomic basal planes of which are oriented perpendicular to the surface thus effecting a high reactivity at the growth front. Subsequently, fine particles or larger parts of the metal surface layer are released, which are buried in the deposited graphite layer on the surface. In case of Inconel 600, containing Cr with mass contents of about 15%, the disintegration can be delayed by the formation of a chromium oxide layer, but no safe protection against metal dusting is obtained.     

Cell death: shadow baxing

Bcl-2, one of a family of key regulators of apoptosis, was the first cell-death machinery component to be identified, but how the family functions is still not clear. Mammalian Bax, a pro-apoptotic family member, can cause yeast cells to die, and two recent yeast genetic screens shed light on how Bax might function.     

Hochleistungsleichtbeton unter mehraxialer Druckbeanspruchung

An vielen Stellen im Tragwerk herrschen mehraxiale Spannungszustände. Ob sich die Tragfähigkeit von Hochleistungsleichtbetonen unter mehraxialer Druckbeanspruchung ebenso erhöht wie bei Normalbetonen, wurde in zwei‐ und dreiaxialen Tests untersucht. Es wurde ein Bruchkriterium für Leichtbetone abgeleitet und Parallelen und Unterschiede zu Normalbeton aufgezeigt. High Performance Lightweight Aggregate Concrete under Multiaxial Compression There are multiaxial stress conditions at many points in a structure. Whether the strength of high performance lightweight concrete under multiaxial compression increases as well as the strength of normal concrete, was verified in bi‐ and triaxial tests. A failure criterion for lightweight concrete was derived and analogies and differences to normal oncrete were pointed out.     

Ranking of refrigerants

Environmental ranking of refrigerants is of need in many instances. The aim is to assess the relative environmental hazard posed by 40 refrigerants, including those used in the past, those presently used, and some proposed substitutes. Ranking is based upon ozone depletion potential, global warming potential, and atmospheric lifetime and is achieved by applying the Hasse diagram technique, a mathematical method that allows us to assess order relationships of chemicals. The refrigerants are divided into 13 classes, of which the chlorofluorocarbons, hydrofluorocarbons, hydrochlorofluorocarbons, hydrofluoroethers, and hydrocarbons contain the largest number of single substances. The dominance degree, a method for measuring order relationships among classes, is discussed and applied to the 13 refrigerant classes. The results show that some hydrofluoroethers are as problematic as the hydrofluorocarbons. Hydrocarbons and ammonia are the least problematic refrigerants with respect to the three environmental properties.