Study of the DC biasing effect on insertion losses in high-frequency interconnections

The paper deals with an experimental investigation of the behavior of high-frequency Si/SiO₂/Al based interconnects when an extra DC bias voltage is applied, by means of which the conductor line changes the surface properties of the semiconductor substrate. By superposing a DC bias to the high-speed signal applied to the line, the insertion losses caused by the semiconductor substrate show a significant decrease over the observed frequency range. In order to study this effect a number of test samples containing several microstrip asymmetric transmission lines were prepared and measured. The obtained results suggest a way of controlling the performance and energy propagation of interconnects on semiconductor substrates. The observed effect can be successfully applied in high-speed blocks with tunable parameters.     

Infrared spectral study of diphenylether polymers

Infrared spectra of polymer, obtained by condensation of diphenylether with formaldehyde in sulphuric acid-alcohol medium are studied. Conclusions about the structure of the oligomer and the thermally treated products are made. A quantitative method for studying the dependence of the kinetics of polycondensation on the temperature and the quantity of the catalyst SnCl₄, is developed.     

Novel microcontacts in microwave chip carriers developed by UV-LIGA process

Design and development of novel type microcontacts in monolithic microwave integrated circuit (MMIC) chip-carriers to printed circuit board (PCB) assembly are presented in this paper. Several new concepts of microcontacts for packaging solutions of microwave and millimeter-wave MMIC are depicted. Simulation and vector network analyzer (VNA) measurement results for these microcontact transitions are discussed and conclusions for the optimal dimensions are made. Equivalent electrical circuits are extracted from the measured S-parameter data. The results show that the electrical parameters are highly dependent on the transition dimensions and substrate features. These contacts are based on male stud (bump) and female ring concept. When mating each other, there are clips effect and self-alignment features. Finally, the article discusses the technological implementation of the proposed new microcontact stud-ring through a low-cost ultraviolet electroplating, lithography, and molding (UV-LIGA) process.     

Band-filling effect on the light emission spectra of InGaN/GaN quantum wells with highly doped barriers

We investigate spectra of InGaN/GaN quantum well (QW) light-emitting diode (LED) structures with heavily doped barriers at different excitation levels. We model the spectral shape and energy position in frames of dominating mechanism of free electron recombination accounting for the influence on the potential width of the QW of the random impurity potential penetrating from the doped barriers. The blue shift at high excitation is supposed to be due to the filling of the conduction band with degenerate 2D non-equilibrium electrons. A structure in the emission bands is observed and it is assumed to be a result from step-like 2D density of states in the QW. A good accordance is obtained between the calculated and experimental spectra assuming that the barriers are graded.     

Effect of carrier concentration on the microhardness of GaN layers

The paper presents a microhardness study of thick crack-free hydride vapor phase epitaxial GaN layers (not intentionally doped), and of thin metal-organic vapor phase epitaxial (MOVPE) GaN layers (undoped and Si-doped), grown on sapphire. A Vickers indentation method was used to determine the microhardness under applied loads up to 2 N. An increase in the microhardness was observed with decreasing carrier concentration and increasing mobility. A dip at an indentation depth of about 0.75 μm is observed in the microhardness profile in the MOVPE films, and is correlated with peculiarities in the spatially resolved cathodoluminescence spectra. The relationship between the mechanical and electrophysical parameters is discussed.     

IR spectra and structures of tellurite glasses

It is shown with IR spectral investigations that the short range order of certain tellurite glasses, obtained from monomineral crystalline phases, is similar to that of the crystals. They may contain the following polyhedra: TeO₄-trigonal bipyramids (C_2v symmetry), deformed TeO₄ groups, TeO₃ trigonal pyramids (C_3v point symmetry), or combinations of these polyhedra. The introduction of V₂O₅ and MoO₃ in the binary glasses leads to a TeO₄ → TeO₃ transition. MoO₃ delays the decay of TeO₄ groups in a wider concentration range.     

Development of horizontal elements in 3-D microcontacts

This paper describes the development and production of horizontal elements in three-dimensional (3-D) microcontacts, implemented in package to PCB assembly. Instead of the standard vacuum deposition process of metal films onto dielectric interfaces, an alternative method aiming at simplicity and lower-cost relative to the technology roadmap, is proposed. This method employs chemical activation and pretreatment of the dielectric photoresist surface with fluid carbon content substance, thus providing also electrical conductivity for direct metal electroplating. A special regime of reverse electrochemical deposition is applied in order to enhance the adhesion of the layer deposited onto the activated surface. This paper presents experimental results of the horizontal elements investigation relative to 3-D microcontacts.     

New assembling technique for BGA packages without thermal processes

A new assembling technique for flip-chip mounting without heating processes was developed. The proposed construction is an FR4 substrate with ring shaped connectors. It is a typical flip-chip technology. The chip is placed, with its active part face-down, directly on to the connecting areas of the substrate. The electrical connection is obtained through a mechanical contact between the ring-shaped clips and the chip bumps. The main advantage of the ring-clip-bump attachment technique is the possibility for multi-chip modules repairing without thermal processes. It is a lead-free assembling technology involving only “conventional” processes.     

Artificially Intelligent Adaptive Search Fast Motion Estimation Algorithm for HD Video

Journal of Signal Processing Systems - This paper presents a new Machine Learning based approach to video Fast Motion Estimation, which improves quality, minimizes power consumption and provides...