Effect of Polyethylene Glycol Additives on Pulse Electroplating of SnAg Solder

Eutectic Sn-3.5wt.%Ag alloy is one of the most promising lead-free solders in low temperature processes for wafer bumping. Near eutectic composition of deposited alloy films could be readily acquired by pulse electroplating with a proper combination of active ingredients including K₄P₂O₇, KI, Sn₂P₂O₇, and AgI, as well as polyethylene glycol (PEG), with molecular weights of 200, 600, 2,000, and 4,000, as an inhibitive agent. Pulse electroplating was carried out with current in alternating polarity to conduct electroplating and electropolishing sequentially. As a result, alloy films with grains of less than 1 μm and uniform surface morphology can be obtained. The addition of PEG was necessary for the stabilization of the plating baths to promote a wider process window for the desirable eutectic composition. Electrochemical characterization established that PEG with molecular weight of 4,000 exhibited the strongest inhibition behavior. In contrast, PEG with molecular weight of 200 demonstrated the least interference. Energy dispersive X-ray and differential scanning calorimeter data confirmed the formation of eutectic alloy as a function of deposition current density. X-ray diffraction results indicated that a biphasic structures of β-Sn and ε-Ag₃Sn was present in the as-deposited film.     

Untersuchung einer Axialturbinen-Stufe mit tangential gekrümmten Leitschaufeln - Teil II: Modellierung für Throughflow-Rechenverfahren

Although today the reality-near flow simulation is possible with 3D Navier-Stokes-Codes also for several stages because of higher computer-performance, nevertheless the computation codes play yet an important role for several stages axialturbines on the basis of the assumption of a rotation-symmetrical flow, in particular for the design engineer in practice. In order to be able to compute such a computing code for the tangential leaned and curved bladings, compatible models of the radial force, models of loss and deflection for this code must be developed with rotational symmetry. With the 3D-numerical and experimental results, mathematical formulations were developed for the new deflection of flow models of this blades, that formally are compatible with the assumption of a rotation-symmetrical flow and with the existing codes.

---

Zusammenfassung Obwohl heuzutage die realitätsnahe Strömungssimulation mit 3D Navier-Stokes-Lösern auch für mehr als eine Stufe möglich ist, spielen für vielstufige Axialturbinen Rechenprogramme auf der Basis der vereinfachenden Annahme einer rotationssymmetrischen Strömung immer noch eine große Rolle, insbesondere für den Auslegungsingenieur in der Praxis. Um ein solches Rechenverfahren für tangential geneigte und gekrümmte Beschaufelungen anwenden zu können, müssen mit der Rotationssymmetrie kompatible Modelle der Radialkraft, Umlenk- und Verlustmodelle für dieses Verfahren entwickelt werden. Mithilfe der Ergebnisse aus den 3D-Berechnungen sowie den experimentellen Daten sind vereinfachte mathematische Formulierungen für die Auswirkungen dieser Beschaufelungen auf Umlenkungen in der Strömung für das vorhandene rotationssymmetrische Rechenverfahren neu entwickelt worden.

---

---

Die hier beschriebenen Ergebnisse wurden im Rahmen einer Dissertation erzielt, die vom Promotionsstipendium nach der Graduiertenförderung der Universität Hannover und vom Institut für Strömungsmaschinen gefördert wurde. Die Schaufeldaten und experimentellen Ergebnisse sind von Prof. Lapschin der TU St. Petersburg zur Verfügung gestellt.     

Enhanced Hole Mobility and Reliability of Panel Epi-Like Silicon Transistors Using Backside Green Laser Activation

The hole mobility and reliability of green continuous-wave laser-crystallized epi-like Si transistors on glass panel substrates were enhanced by source/drain activation by backside green laser irradiation. Green laser energy was scanned uniformly across junctions since the gate structures included no interference, in an attempt to conduct super visible-laser lateral activation. The enhancement was thus explained by the formation of continuous improved epi-like Si microstructures with reduced grain defects and with a barely increased number of interface defects over the entire channel/junction. The hole mobility in such laser-activated devices was as high as 403 cm² /V^.s, which doubles that of thermally activated devices.     

Micro-optics for liquid crystal displays applications

Micro-optics have become the key technology in liquid crystal display systems due to its capabilities of miniaturization and design flexibility. Design consideration and experimental results of microoptical components for enhancing the image quality, providing better functions, increasing light efficiency, and generating 3D images in liquid crystal display (LCD) applications are presented.     

Inhibitory effect of pulmonary surfactant proteins A and D on allergen-induced lymphocyte proliferation and histamine release in children with asthma

The role of pulmonary surfactant proteins in the pathogenesis of airway inflammation and the impact on asthma has not been elucidated. This study was designed to examine the effect of surfactant proteins A (SP-A) and D (SP-D) on phytohemagglutinin- (PHA) and mite allergen Dermatophagoides pteronyssinus (Der p)-induced histamine release and the proliferation of peripheral blood mononuclear cells (PBMC) in children with asthma in stable condition (n = 21), asthmatic children during acute attacks (n = 9), and age-matched control subjects (n = 7). The results show that SP-A and SP-D were able to reduce the incorporation of [3H]thymidine into PBMC in a dose-dependent manner. In addition to the intact, native SP-A and SP-D proteins, a recombinant peptide composed of the neck and carbohydrate recognition domain (CRD) of SP-D [SP-D(N/CRD)] was also found to have the same suppressive effect on lymphocyte proliferation. This effect was abolished by the presence of 100 mM mannose (for SP-A) or maltose (for SP-D) in the culture medium, which suggested that the CRD regions of SP-A and SP-D may interact with the carbohydrate structures on the surface molecules of lymphocytes. The inhibitory effects of surfactant proteins on PHA- and Der p-stimulated lymphocyte responses were observed in stable asthmatic children and age-matched control subjects, while only a mild suppression (< 25%) was seen in activated lymphocytes derived from asthmatic children with acute attacks. SP-A and SP-D were also found to inhibit allergen-induced histamine release, in a dose-dependent manner, in the diluted whole blood of asthmatic children. We conclude that both SP-A and SP-D can inhibit histamine release in the early phase of allergen provocation and suppress lymphocyte proliferation in the late phase of bronchial inflammation, the two essential steps in the development of asthmatic symptoms. It appears that SP-A and SP-D may be protective against the pathogenesis of asthma.     

On the bid price curve of intra-urban business

This paper is an attempt to generalize the bid price curve of urban firms by considering the production and demand oriented theories together. By applying the powerful envelope theorem, we derive the basic properties and the shape of the bid price curve. Contrary to Alonso, Mai and Richardson, we show that the bid price curve can be straightline, convex to the origin or concave to the origin.The author is indebted to Professors R.Anderson, J. Lim and C. C. Mai. Responsibility for all errors is the author's.     

Photoconductivity effects in CuInS2, CuInSe2 and CuInTe2 thin films

Photoconductivity response spectra for CuInS₂, CuInSe₂ and CuInTe₂ thin films are reported. The temperature dependences of the spectra are utilized to determine the bandgap energies as functions of temperature. Photoconductive response times are measured for these I–III–VI₂ ternary semiconductors and are discussed in terms of deposition parameters and post-deposition treatments. The photoconductive decay times are in the range 10^-3 – 10¹ ms.