Predicting the relationship between reliability and geometric parameters of cu column bumped flip-chips

Cu column bumping is a novel flip chip packaging technique that allows Cu columns to be bonded directly with the dies. It has eliminated the under-bump-metallurgy (UBM) fonnation step of the traditional flip chip manufacturing process. This bumping technique has the potential benefits of simplifying the flip chip manufacturing process, increasing productivity and the UO counts. In this paper, a study of reliability of Cu column bumped flip chips will be presented. Computer modelling methods have been used to predict the shape of solder joints and the response of flip chips to cyclic thermal-mechanical loading. The accumulated plastic strain energy at the corner solder joints has been used as an indicator of the solder joint reliability. Models with a wide range of design parameters have been compared for their reliability. The design parameters that have been investigated are the copper column height and radius, PCB pad radius, solder volume and Cu column wetting height. The relative importance ranking of these parameters has been obtained. The Lead-free solder material 96.5Sn3.5Ag has been used in this modelling work.

The presence of the Aragonese language in the magazine "El Ebro" (1917-1936)

El Ebro (1917-1936) was a magazine published in Barcelona by Aragonese emigrants at the beginning of the 20th century. It was the first experience of coexistence of different dialectal varieties of the Aragonese language in the same media. El Ebro was an experience that has gone virtually unnoticed in the recent history of one of the most minority languages, and with minor media presence, of Western Europe. In its pages El Ebro mixed dialects spoken in different regions of linguistic Aragonese area together with transcripts of medieval documents. At the same time, this newspaper raised debates about the language issue that they were truncated due to disappearance of the publication and the lack of theoretical realization

The Unexpected Preference for the fac-Isomer with the Tris(5-ester-substituted-2,2′-bipyridine) Complexes of Ruthenium(II)

The synthesis of a number of new 2,2'-bipyridine ligands, functionalized with bulky ester side groups is reported (L2 - L8). Their reaction with [Ru(DMSO)4Cl2] gives rise to tris-chelate ruthenium(II) metal complexes which show an unusually high proportion of the fac-isomer, as judged by 1H NMR following conversion to the ruthenium(II) complex of 2,2'-bipyridine-5-carboxylic acid methyl ester (L1). The initial reaction appears to have thermodynamic control with the steric bulk of the ligands causing the third ligand to be labile under the reaction conditions used, giving rise to disappointing yields and allowing rearrangement to the more stable facial form. DFT studies indicate that this does not appear to be as a consequence of a metal centered electronic effect. The two isomers of [Ru(L1)3](PF6)2 were separated into the two individual forms using silica preparative plate chromatographic procedures, and the photophysical characteristics of the two forms compared. The results appear to indicate that there is no significant difference in both their room temperature electronic absorption and emission spectra or their excited state lifetimes at 77K.

Enantiocomplementary preparation of (S)- and (R)-1-pyridylalkanols via ketone reduction and alkane hydroxylation using whole cells of Pseudomonas putida UV4

A previously unreported alcohol dehydrogenase enzyme in the mutant soil bacterium Pseudomonas putida UV4 catalyses the reduction of 2-, 3- and 4-acylpyridines to afford the corresponding (S)-1-pyridyl alkanols, with moderate to high e.e., whilst under the same conditions 2,6-diacetylpyridine is readily converted to the corresponding enantiopure C2-symmetric (S,S)-diol in one step. In contrast, the toluene dioxygenase enzyme in the same organism catalyses the hydroxylation of 2- and 3-alkylpyridines to (R)-1-(2-pyridyl) and (R)-1-(3-pyridyl)alkanols. This combination of oxidative and reductive biotransformations thus provides a method for preparing both enantiomers of chiral 1-pyridyl alkanols using one biocatalyst.

Synthesis of Piano Stool Complexes Employing the Pentafluorophenyl Substituted Diphosphine (C6F5)2PCH2P(C6F5)2 and the Effect of Phosphine Modifiers on Hydrogen Transfer Catalysis.

Ruthenium, rhodium, and iridium piano stool complexes of the pentafluorophenyl-substituted diphosphine (C6F5)2PCH2P(C6F5)2 (2) have been prepared and structurally characterized by single-crystal X-ray diffraction. The Cp-P tethered complex [{(C5Me4CH2C6F4(C6F5)CH2P(C6F5)2}RhCl2] (9), in which only one phosphorus is coordinated to the rhodium, was prepared by thermolysis of a slurry of [Cp*RhCl(-Cl)]2 and 2 and was structurally characterized by single-crystal X-ray diffraction. The tethering occurs by intramolecular dehydrofluorinative coupling of the pentamethylcyclopentadienyl ligand and P,P-coordinated 2. The geometric changes that occur on tethering force dissociation of one of the phosphorus atoms. The effects of introducing phosphine ligands to the coordination sphere of piano stool hydrogen transfer catalysts have been studied. The complexes of fluorinated phosphine complexes are found to transfer hydrogen at rates that compare favorably with leading catalysts, particularly when the phosphine and cyclopentadienyl functionalities are tethered. The highly chelating Cp-PP complex [(C5Me4CH2-2-C5F3N-4-PPhCH2CH2PPh2)RhCl]BF4 (1) was found to outperform all other complexes tested. The mechanism of hydrogen transfer catalyzed by piano stool phosphine complexes is discussed with reference to the trends in activity observed.

Base free dynamic kinetic resolution of secondary alcohols using ‘piano stool’ complexes of N-heterocyclic carbenes

Piano stool complexes of rhodium and iridium activated by fluorinated and non-fluorinated N-heterocyclic carbene (NHC) ligands were shown to be catalysts for racemization in the one-pot chemoenzymic dynamic kinetic resolution (DKR) of secondary alcohols. Excellent conversions and good enantioselectivities were observed for alkyl aryl and dialkyl secondary alcohols.

Competence in research planning in the fourth level of Spanish Secondary Education: a case study

In the last years, “Inquiry-Based Science Education” methodologies (IBSE) are being recommended by European institutions in order to improve the competence levels and the attitudes towards science of primary and secondary school students. Therefore, the aim of this study is to test the effectiveness of an IBSE methodology, the Methodology of Problem Solving as an Investigation (MPSI), for the teaching-learning process of planning of experiments in the fourth level of Spanish Secondary Education. By means of the students’ solutions for a series of open problems, the progress in the learning of the competences related to the planning of experiments has been analyzed, along with the influence of the methodology on the development of these competencies. The results show a students’ command from higher to lower levels on: emission of hypothesis, design of the experiment, qualitative analysis, identification of variables and reformulation of the open problem. Furthermore, the Methodology has contributed to an improvement of the scientific competence in the area of planning experiments.

Isotopic assessment of sources and processes affecting sulfate and nitrate in surface water and groundwater of Luxembourg

Surface water and deep and shallow groundwater samples were taken from selected parts of the Grand-Duchy of Luxembourg to determine the isotopic composition of nitrate and sulfate, in order to identify sources and/or processes affecting these solutes. Deep groundwater had sulfate concentrations between 20 and 40 mg/L, d34Ssulfate values between -3.0 and -20.0‰, and d18Osulfate values between +1.5 and +5.0‰; nitrate was characterized by concentrations varying between