Surface Engineering and Applied Electrochemistry最新文献

The results of an approximate calculation of the averaged values of speeds of v_mz of a longitudinal drift of lone electrons, of circular frequencies of ω_mz change of longitudinal electronic de Broglie waves, and of lengths of λ_mz of longitudinal electronic de Broglie waves in the metal of a round cylindrical conductor with an electric axial-flow current of conductivity of i₀(t) of different kinds (permanent, variable, and impulsive) and amplitude-time parameters (ATP) are presented. The results of verification of the obtained calculation correlations for speeds of v_mz drift of lone electrons and lengths of λ_mz of electronic de Broglie waves in the examined conductor demonstrate their validity and working capacity. The obtained data confirm the quantum-wave nature of the electric current of conductivity of the indicated kinds of i₀(t) and of ATP in a metallic conductor.

To increase the effectiveness of various electrochemical energy conversion and storage systems, electroactive and affordable electrocatalysts must be developed. Herein, the developed ultrasonic approach in the design and synthesis of the Fe-based spinel oxide (Fe₃O₄, CdFe₂O₄, CrFe₂O₄, and Cd_0.2Cr_0.8Fe₂O₄) nano-boxes, whose electrochemical performance was studied, is reported. The X-ray diffraction patterns proved the presence of the complete solitary-phase nano-spinel oxides. The Fourier-transform infrared spectra also supported the developed oxide structures. The thermogravimetric analysis showed a notable decline in the sample’s weights, with the most significant weight loss observed at approximately 35.46%. The cyclic voltammetry and the Tafel measurements were applied to investigate the electrochemical merits of the synthesized nanoparticles on a titanium supported electrode for different electrocatalytic applications. The results from cyclic voltammetry revealed that the substitution of the A site of the Fe atom with Cr or Cd had a detrimental impact on the current density value, and the ferrite with only chromium substitution exhibited the minimal current density at 0.7 V. The electrocatalytic activity estimated by Tafel curves towards an oxygen evolution reaction, ethanol and methanol oxidation reactions showed that the ternary ferrite with cadmium and chromium substitution (Cd_0.8Cr_0.2Fe₂O₄) had the highest current density of 0.224 mA/cm² at 850 mV towards an oxygen evolution reaction and was the most active towards a methanol oxidation reaction.

The rapid breakdown anodization process was used to modify the copper surface. The effects of the chemical solution mechanical movement (CSMM), anode edge isolation, applied voltage, and activity of hydrogen ions in the solution on the morphology of anodized copper were studied. The X-ray diffraction test confirmed the formation of Cu₂O on the anode as the dominant phase. Increasing the applied voltage changed the ratio of the produced Cu₂O powders phases. The CSMM and the isolation of samples edges did not affect the type of the powder components or their ratio, but the applied voltage did. The CuO phase appeared only when the anode became outside the container. The shapes of the produced particles on the anode were cubic or irregular sphere depending on the applied conditions. Rather than in the solution, the growth of cubic forms took place on the anode itself. The particles formed on the cathode had the same shapes as those found in powders. When the CSMM was absent, the applied voltages had less influence on corrosion; but when edges were exposed, the effect was greater. The obtained results revealed increases in the corrosion activity at low pH values.

In order to increase the service life of critical products made of refractory metals, the most effective is the use of protective coatings based on oxidation-resistant ceramic materials. Using an electrode/target made of heterophase HfSi₂–MoSi₂–HfB₂ ceramics by electrospark deposition (ESD), high-power impulse magnetron sputtering (HIPIMS) technologies, as well as the combined ESD + HIPIMS technology, coatings were deposited onto molybdenum substrate (MCh-1 brand). Electrode materials and coatings were studied by the X-ray diffraction, the glow discharge optical emission spectroscopy, the X-ray spectral microanalysis, and the scanning electron microscopy. Combined ESD + HIPIMS technology made it possible to create a hard layer of oxidation-resistant ceramics on the surface of the substrate, which does not produce through cracks inherent in ESD coatings.

Surface mounting, as a constructive-technological approach in miniaturizing fourth-generation electronic equipment, has yielded significant advancements. These include the miniaturization of structural elements, a two- to three-fold increase in mounting density, decreased material consumption, and enhanced resistance to vibration—a critical factor ensuring equipment reliability. Shortening the lead length has correspondingly diminished parasitic inductance, capacitance, and resistance, thereby improving electrical parameters and bolstering equipment reliability. This chapter presents a classification of surface mounting varieties and discusses the technological equipment used for applying solder paste, placement and soldering components. The soldering of SMD components using solder pastes necessitates precise individual temperature profiling of heating for each board size, typically facilitated by a microcontroller. Soldering modes, governed by the melting of solder pastes, are determined by a temperature–time diagram, which is meticulously optimized for IR ovens with multiple heating zones. The chapter also addresses the primary defects encountered in surface mounting processes and delineates measures for their effective elimination.

The examination of structural and technological features of microwave (MW) modules, along with trends in their development, is a focal point of this chapter. Detailed descriptions are given concerning the technological operations entailed in assembling MW microblocks, capable of operating at frequencies up to 20 GHz, inclusive of vibrational and ultrasonic soldering. Investigative efforts delve into dependences concerning the degree of wetting of microstrips in response to exposure time to ultrasonic (US) vibrations. These investigations reveal that optimal wetting within a 15-s timeframe is achieved for Sn–Pb solder and galvanic coating with a tin–bismuth alloy. This favorable outcome is attributed to the superior fluidity exhibited by this solder in comparison to Sn–In solder, as well as the absence of intermetallic formation during the soldering process of tin–bismuth coatings, which deteriorates the wetting process, as in the case of gold coatings. The implementation of US vibrations in pulse mode, characterized by pulse frequencies ranging from 0.5 to 10 Hz and depths of 2 to 6, aims to mitigate the formation of wave superpositions leading to the development of nodes and lobes of displacement amplitude in the solder. By localizing a homogeneous cavitation process within the molten solder, this methodology facilitates the simultaneous destruction of oxide films across the entire soldered surface of the microstrip board, thereby creating conducive conditions for complete wetting of the board surface by the solder, without the use of fluxes. The use of high-frequency heating in combination with a ferrite magnetic circuit during the sealing of microblock packages composed of diamagnetic alloys is explored. This approach serves to enhance process efficiency, augment the reliability of microelectronic devices, and facilitate the substitution of lead-free solders for conventional tin–cadmium and tin–bismuth solders, thus addressing environmental concerns and regulatory requirements.

To ensure the formation of high-quality solder joints, it is imperative to engage in surface preparation of the materials being joined, activate both the materials and solder, eliminate oxide films in the contact zone, facilitate interaction at the interfacial boundary, and induce crystallization of the liquid metal layer. This chapter delves into the processes involved in removing surface oxide films from solderable surfaces and discusses the pertinent equipment employed. Additionally, it highlights the potential efficacy of ultrasonic methods in oxide film removal through the introduction of elastic mechanical vibrations into the molten solder. Mathematical expressions are derived to elucidate the dynamics at the solder-surface interface, during the capillary penetration of solder into gaps and the diffusion process. The formation of a soldered joint with a specific structure results from the physicochemical interaction between the solder and the base metal. This joint typically encompasses a melting zone and diffusion zone at the solder and the base metal interface. The ultimate structure and composition of the solder joint depend on the nature of the interacting metals, their chemical affinity, and the soldering conditions, including time and temperature.

Wire bonding remains a primary method for assembling integrated circuits and micromodules due to its high process automation and versatility across manufacturing technological options, as well as the geometric dimensions of the products. Significant progress has been made in the development of interconnection methods in integrated electronic devices, mitigating the complexity of these operations and notable successes towards their full automation. Various processes such as thermocompression bonding, ultrasonic (US) bonding, and thermo-ultrasonic bonding during the assembly of integrated circuits and micromodules are extensively examined. The characteristics of automatic equipment for bonding, along with the peculiarities of the tools employed, are provided for comprehensive understanding. In ultrasonic bonding, mechanical vibrations of ultrasonic frequency are introduced into the contact zone, resulting in the plastic deformation of the wire lead and the removal of oxide films, thereby creating atomically clean juvenile surfaces. This process intensifies the formation of active centers during the bond formation without significant wire deformation or substantial heating. Thermo-ultrasonic bonding involves the combined action of ultrasonic energy, tool loading force, and heating temperature up to 200–220°C. This combination enhances the reproducibility of bond quality and eliminates sensitivity to variations in the properties of the materials being bonded, leading to more consistent and reliable results.

This chapter explores the evolving trends in contemporary electronic module designs and assembly technologies. The enhancement of computer technology and digital communication tools, coupled with the escalation in the operational speed of the elemental base, hinges directly on the reduction of signal transmission length between logical elements, i.e., the constructive delay of the transmitted signal. Interconnection technology, crucial for bridging the microcosm of semiconductor chips with the external world of electronic devices, emerges as pivotal for producing viable products. We provide a comprehensive classification and discussion of assembly connection designs, employing methods involving direct material contact under the influence of pressure, heat, and physical impact in various combinations. Intermediate materials such as solder, microwires, and conductive adhesives are utilized in these processes. Special emphasis is placed on surface mounting of electronic components, COB assembly technology, Flip Chip, BGA, and the assembly of multichip electronic modules.

This chapter delineates detailed methods and tools for the visual inspection of soldered joints. It enumerates the primary types of defects and the capabilities of automatic visual and electrical inspection for their detection and highlights the use of automatic equipment for thermographic, acoustic, and X-ray inspection of soldered and microsoldered joints. The methodology for monitoring transient electrical resistance in contact connections is also examined. For automatic electrical inspection of connections, systems equipped with flying probes are used. These systems supply power and receive signals from the inspected connection on the board or component, automatically verifying functionality. The criteria for assessing the strength of soldered joints include the magnitude of the pull-off force, the durability of the joints under alternating loads, and vibration resistance. Destructive testing is employed to ascertain the mechanical and physico-mechanical properties of soldered joints. In metallographic inspection, the diffusion zone between the solder and the base metal is identified, and the quality of the soldered joint is assessed based on its width. Typical defects of soldered joints and their causes are considered.