Interconnections in Multilayer PCBs Based on Microvias Metallized by Magnetron Sputtering Deposition
The high advanced miniaturization of electronic components determines designers and producers of PCBs (printed circuit boards) to search the new constructions and technologies of HDI (high density interconnect) PCBs manufacturing. The researches are concentrated on the problems of miniaturization of PCBs interconnections. Many possibilities in this area are created by using microvia technology. The microvias can be made by using several techniques of drilling, but the great problem in this aspect is connected with possibilities of proper and repeatable metallization of microvias. Wide practical techniques of metallization allow to properly metallize of blind microvias which aspect ratio (deep/diameter of microvia) is about 1 or less. In the paper we propose the use of the magnetron sputtering deposition of copper to metallize the high aspect ratio blind microvias. During tests the use of magnetron self-sustaining mode also was investigated. This special mode allow to deposit of thin and very clear (without labour gas particles) electro-conductive layers which can be grown in electroplating processes
Plasma parameters of very high target power density magnetron sputtering
Abstract The high target power density (up to ∼1000 W cm −2 ) of a magnetron sputtering process was studied by means of optical emission spectroscopy and Langmuir probe characteristics. The goal of this research was to estimate the composition (neutrals and ions) and parameters of the plasma (temperature T e and density n e of electrons) at different technological parameters. Copper targets with a diameter of 50 and 100 mm were sputtered. The argon pressure was changed from 0 (final pressure equal to 1×10 −5 torr) to 5×10 −3 torr. This corresponded to self-sustained (at the final vacuum pressure) and standard argon sputtering modes, respectively. The dominant role of copper ions was observed (404.3 + nm ion line intensity in relation to 402.3 * and 406.3 * excited neutrals line intensities) during both the self-sustained and argon modes of high target power density. The line intensity of copper ions near the etched target surface (cathode voltage fall) increased substantially when the target current increased. The substrate current density (at a distance between target and substrate equal to 9 cm) increased significantly with the decrease of the parallel component of the magnetic field intensity (at constant target current). At this distance, a sputtering rate of ∼5 μm min −1 was achieved for the Cu target of 50 mm in diameter.
An automated retinal image quality grading algorithm
This paper introduces an algorithm for the automated assessment of retinal fundus image quality grade. Retinal image quality grading assesses whether the quality of the image is sufficient to allow diagnostic procedures to be applied. Automated quality analysis is an important preprocessing step in algorithmic diagnosis, as it is necessary to ensure that images are sufficiently clear to allow pathologies to be visible. The algorithm is based on standard recommendations for quality analysis by human screeners, examining the clarity of retinal vessels within the macula region. An evaluation against a reference standard data-set is given; it is shown that the algorithm's performance correlates closely with that of clinicians manually grading image quality.