Formation of Pb/63Sn solder bumps using a solder droplet jetting method

Formation processes of Pb/63Sn solder droplets using a solder droplet jetting have not been sufficiently reported. Solving problems such as satellite droplets and position errors are very important for a uniform bump size and reliable flip-chip solder bump formation process. First, this paper presents the optimization of jet conditions of Pb/63Sn solder droplets and the formation process of Pb/63Sn solder bumps using a solder droplet jetting method. Second, interfacial reactions and mechanical strength of jetted Pb/63Sn solder bumps and electroless Ni-P/Au UBM joints have been investigated. Interfacial reactions have been investigated after the second solder reflow and aging, and results were compared with those of solder bumps formed by a solder screen-printing method. Third, jetted solder bumps with variable bump sizes have been demonstrated by a multiple jetting method and the control of waveform induced to a jet nozzle. Multiple droplets jetting method can control various height and size of solder bumps. Finally, real applications of jetted Pb/63Sn solder bumps have been successfully demonstrated on conventional DRAM chips and integrated passive devices (IPDs).     

Probing intermediates in the reaction of ethylene over supported Ru; use and limitations of multiple quantum spin counting

Multiple quantum spin counting is shown to yield an upper limit ofn = 6 for strongly bound, rigid intermediates C _m H _n in the reaction of ethylene over Ru/SiO₂. The results eliminate the possibility of major components of such intermediates being polymer-like coke precursers. A precurser to 2-butene is one possible intermediate.     

Efficacy of measles vaccine during the 1993 measles epidemic in Korea

Immunization to eliminate measles is recommended at 15 months of age with the option of giving vaccine at 6 to 9 months of age during measles outbreaks in Korea. Because of the recent resurgence of measles and concern about the possibility of reduced vaccine efficacy caused by genomic differences between vaccine virus and contemporary wild measles viruses, we conducted a measles vaccine efficacy study involving children with household exposure ages 1 to 5 years during measles outbreak that had occurred 1993 in Seoul and Seong-nam city, with the demographic analysis of patients brought to the hospitals. A total of 380 patients (M:F = 216:164) were included in this study. Two hundred nine cases (55.0%) occurred in children less than 5 years of age, and 167 (43.9%) were younger than 16 months of age. The recorded age-specific incidence rates showed bimodal patterns, i.e. highest peak in those below 16 months of age and second peak in those ages 6 to 9 years of age. Only 9.6% (16 of 167) of the measles cases less than 16 months, 59.5% (25 of 42) of those 16 months to 4 years and 91.8% (157 of 171) of the cases in school age children have been vaccinated. Attack rates among the 122 vaccinated siblings and 12 unvaccinated siblings ages 1 to 5 years who contacted measles were 5.7 and 75%, respectively, and the clinical vaccine efficacy was 92.4% (95% confidence interval, 83.6, 96.4). The high vaccine efficacy in household exposures suggests that measles outbreaks in Korea are not caused by reduced vaccine efficacy.     

An adaptive checkpointing scheme for distributed databases withmixed types of transactions

A checkpointing algorithm that is noninterfering with transaction processing is presented. It prevents the well-known domino effect and saves the intermediate results of a long-lived transaction in an adaptive manner, managing effectively both short- and long-lived transactions in the system     

Laser Raman studies of α–bromoacrylamide reactive dyes and wool

The use of laser Raman spectroscopy in the investigation of interactions in α–bromoacrylamide reactive dye–wool fibre systems has been established. The spectra obtained (in particular using C. I. Reactive Red 84) provide some evidence to support the proposal that the dye reacts via addition at the double bond of the reactive group, followed by ring closure through nucleophilic substitution. Furthermore, preliminary studies of the effect of the commercial levelling assistant Albegal B on the aqueous dye environment have been made using C. I. Reactive Yellow 39. The results show that, whilst the primary interaction between the dye and auxiliary may be via the water–solubilising sulphonate groups of the dye, hydrophobic interactions are also important.     

Vapor-air discharges between electrolytic cathode and metal anode at atmospheric pressure

Experimental investigation is performed of the structures and electrical characteristics of vapor-air discharges between a metal (solid, hollow, pointed) anode and an electrolytic cathode at atmospheric pressure. Singular features are revealed of free vapor-air discharges with an electrolytic cathode and their relative transition. Analysis and generalization of the experimental results enable one to reveal the basic physical processes which define the possible mechanism of maintaining a vapor-air discharge with an electrolytic cathode.Translated from Teplofizika Vysokikh Temperatur, Vol. 43, No. 1, 2005, pp. 005–010. Original Russian Text Copyright © 2005 by A. F. Gaisin and E. E. Son.     

An Integration of Source and Jammer for a Decode-and-Forward Two-way Scheme Under Physical Layer Security

In this paper, we propose and analyze the integration of source and jammer for a decode-and-forward two-way scheme under physical layer security where the source nodes not only transmit data signals, but also transmit jamming signals to degrade the quality of eavesdropping links, and a selected relay forwards the combined data signals using an XOR operation. In this proposed protocol, the best relay is chosen by the maximum end-to-end achievable secrecy rate, and the secrecy system performance is evaluated by the exact and asymptotic secrecy outage probability over flat and block Rayleigh fading channels. The Monte-Carlo results are presented to verify the theoretical analysis.     

Controlled hydrothermal growth of multi-length-scale ZnO nanowires using liquid masking layers

In this study, we demonstrate a method for creating multi-length-scale ZnO nanowires in a controllable manner on diverse planar and curvilinear substrates by introducing immiscible liquid masking layers (LMLs) above and beneath a nutrient solution used in hydrothermal growth. The confinement of volatile reactants by the LMLs stabilizes the pH, which is an important parameter in determining the shape of the nanowires, to enable growth in a stable manner. The conformal wettability of the LMLs provides freedom in the choice of target substrates and allows for the possibility of mounting spatially moving stages without the use of a specially designed solid lid. Selective growth within the growth zone defined by the LMLs in a dynamic- and/or static-mode can create various types of ZnO nanowires with gradual or terraced length profiles in two- or three-dimensional geometries. For a device application, we developed cylindrical photodetectors with the configuration of Cr/ZnO seed/ZnO nanowires/poly(3-hexylthiophene-2,5-diyl)/poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) to show the ability to spatially modulate the photo-sensitivity by controlled hydrothermal growth of diverse length scales of ZnO nanowires using the LML method.