Influence of the Cathode Surface Geometry on the Metal Pad Current Density

2014 ◽  
pp. 477-484 ◽  
Author(s):  
Marc Dupuis ◽  
Valdis Bojarevics
Keyword(s):  
Current Density ◽  
Cathode Surface ◽  
Surface Geometry

RESTORATION OF MACHINE PARTS WITH GALVANIZED ZINC COATINGS

2020 ◽  
Vol 4 (141) ◽  
pp. 140-147
Author(s):  
MIKHAIL VIKHAREV ◽  
◽  
VLADIMIR YUDIN ◽  
VESELOVSKIY NIKOLAY ◽  
◽  
...  
Keyword(s):  
Current Density ◽  
Cathode Surface ◽  
Zinc Coating ◽  
Cathode Current Density ◽  
Research Purpose ◽  
Cathode Layer ◽  
Properties Of Coatings ◽  
Chemical Polarization ◽  
Cathode Current ◽  
Zinc Coatings

The article shows the role of electroplating in the restoration of parts, indicates the advantages of restoring parts with electroplating over other methods, and gives the characteristics and properties of coatings obtained by electroplating. (Research purpose) The research purpose is in increasing the speed of application of zinc electroplating when restoring parts. (Materials and methods) The cathode current density has a decisive influence on the coating speed. The main reason for limiting the cathode current density during galvanizing from sulfuric acid electrolytes is the chemical polarization of the cathode. The article presents a study on the designed installation for the application of galvanic coatings. When applying coatings to the internal surfaces of parts, there was used a device with activating elements having an electromechanical rotation drive. This device prevents depletion of the near-cathode layer of the electrolyte and reduces the chemical polarization of the cathode. Elements made of moisture-resistant skin were used as activators. (Results and discussion) The article presents the results of experiments as a dependence of the coating speed on the speed of the activator relative to the restoring surface. It also presents the relationship between the size of the abrasive grains of the activating elements, the force of their pressing against the cathode surface, the speed of movement of the activator and the speed of applying the zinc coating, as well as its quality. By activating the cathode surface, it was possible to raise the operating current density to 100-150 amperes per square decimeter. The speed of application of zinc coatings is 16-25 micrometers per minute. (Conclusions) In the course of research, authors determined the conditions of electrolysis during galvanizing, which provide a significant increase in the cathode current density and the rate of application of these coatings during the restoration of parts.

CATHODE SURFACE CHANGES IN THE PRESENCE OF GELATIN DURING ELECTRODEPOSITION OF COPPER

1943 ◽  
Vol 21b (6) ◽  
pp. 125-132 ◽  
Author(s):  
W. Gauvin ◽  
C. A. Winkler
Keyword(s):  
Grain Size ◽  
Current Density ◽  
Copper Sulphate ◽  
Cathode Surface ◽  
Active Area ◽  
Cathode Polarization ◽  
Active Centres ◽  
Main Factor ◽  
Surface Changes

Measurements of the cathode polarization during electrodeposition of copper from acid copper sulphate solutions indicate that introduction of gelatin into the electrolyte decreases the area of the cathode available for deposition, or active area, owing to adsorption of gelatin on the active centres. This decrease in area causes an increase in the true current density, with a resulting increase in cathode polarization, the former being assumed the main factor in causing an increase in the rate of nuclear formation and decrease in grain size.

scholarly journals Theoretical Study of a 0.22 THz Backward Wave Oscillator Based on a Dual-Gridded, Carbon-Nanotube Cold Cathode

2018 ◽  
Vol 8 (12) ◽  
pp. 2462 ◽  
Author(s):  
Qingyun Chen ◽  
Xuesong Yuan ◽  
Matthew Cole ◽  
Yu Zhang ◽  
Lin Meng ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Output Power ◽  
Current Density ◽  
Compression Ratio ◽  
Cathode Surface ◽  
Electron Gun ◽  
Cold Cathode ◽  
Backward Wave Oscillator ◽  
Wave Oscillator ◽  
Backward Wave

The carbon nanotube (CNT) cold cathode is an attractive choice for millimeter and terahertz vacuum electronic devices owning to its unique instant switch-on and high emission current density. A novel, dual-gridded, field emission architecture based on a CNT cold cathode is proposed here. CNTs are synthesized directly on the cathode surface. The first separating grid is attached to the CNT cathode surface to shape the CNT cathode array. The second separating grid is responsible for controlled extraction of electrons from the CNT emitters. The cathode surface electric field distribution has been improved drastically compared to conventional planar devices. Furthermore, a high-compression-ratio, dual-gridded, CNT-based electron gun has been designed to further increase the current density, and a 21 kV/50 mA electron beam has been obtained with beam transparency of nearly 100%, along with a compression ratio of 39. A 0.22 THz disk-loaded waveguide backward wave oscillator (BWO) based on this electron gun architecture has been realized theoretically with output power of 32 W. The results indicate that higher output power and higher frequency terahertz BWOs can be made using advanced, nanomaterial-based cold cathodes.

Study of Void Formation Mechanism in Electroplated SnAg Solder Bump

2016 ◽  
Vol 2016 (1) ◽  
pp. 000638-000643
Author(s):  
Koji Tatsumi ◽  
Akio Sakai ◽  
Syunsuke Kawai ◽  
Takuma Katase ◽  
Takashi Miyazawa ◽  
...  
Keyword(s):  
Formation Mechanism ◽  
Electrolyte Solution ◽  
Current Density ◽  
Solder Bump ◽  
Cathode Surface ◽  
Void Formation ◽  
Gas Generation ◽  
Solder Bumps ◽  
Snag Solder ◽  
The Cross

Abstract SnAg electroplating method is widely used in the formation of LF solder bump for flip chip connection. While electroplating is able to form void free solder bump in a suitable operating condition, void may occur suddenly when used in mass production. This study aims at understanding the gas source in the void of electroplated SnAg solder bumps and determining the manufacturing process factors which affect the void formation. There are various types of void formation mode. One mode is H2 gas generation on cathode surface during electroplating. Both the cross-sections of solder bumps, as well as an analysis data of the gas in the void taken by the TDS (Thermal Desorption Spectrometry) were evaluated. The cross-section of the solder bump which contains void due to the reflow process revealed the existence of several tens of nm to several μm size pits in the solder bump before reflow. TDS analysis indicates that the pits consisted of mainly H2O, H2 and the decomposition of organics. A possible void formation mechanism is the evaporation of H2 gas and the incorporated electrolyte solution in the bump by reflow. These pits in the solder were caused by various process parameters. One of the causes is due to the setting of the current density in the SnAg electroplating process being inappropriate. The current density should be adjusted corresponding to the electrolyte performance and bump design such as PR thickness, opening diameter and bump density. The computer simulation demonstrated that a thick PR limits the diffusion of the Sn2+ ions into via holes and having the current density too high causes a lack of Sn2+ ions on the cathode surface and causes H2 gas generation. The other mode of void formation is Ag displacement of the under bump metallization (UBM) surface in dwell time in the SnAg electrolyte solution before the start of plating. The adjustment of each process parameter can eliminate the source of the void and achieve a high reliability of SnAg bump formation.

scholarly journals Space-Charge Limitation of a Femtosecond Photoinjector

2011 ◽  
Vol 2011 ◽  
pp. 1-5 ◽  
Author(s):  
Hiroko Yamamoto ◽  
Hiroaki Hamabe ◽  
Shintaro Sone ◽  
Soichiro Yamaguchi ◽  
Makoto R. Asakawa
Keyword(s):  
Experimental Investigation ◽  
Space Charge ◽  
Current Density ◽  
Cathode Surface ◽  
Laser Pulses ◽  
Space Charge Limited Current ◽  
Electron Bunches ◽  
Surface Field ◽  
Simple Physical Model ◽  
Fs Laser

Experimental investigation of a compact 40-kV diode-type photoelectric DC gun driven by 100 fs laser pulses revealed that the space-charge-limited current density could exceed 30 kA/cm2and that the density increased linearly with the accelerating voltage. We explained these important properties by the balance between the cathode surface field and the field produced by sheet-like electron bunches near the cathode surface. Our simple physical model agreed well with the experimental results.

Effects of Cathode-Mandrel Surface Irregularities on the Mechanical Properties and Structure of Electroformed Iron Foil

1980 ◽  
Vol 22 (2) ◽  
pp. 49-54 ◽  
Author(s):  
W. A. Crichton ◽  
J. A. McGeough ◽  
J. R. Thomson
Keyword(s):  
Surface Roughness ◽  
Current Density ◽  
Cathode Surface ◽  
Foil Thickness ◽  
Iron Foil ◽  
Surface Irregularities ◽  
The Face ◽  
The Relationship ◽  
A Current ◽  
Cathodic Surface

Iron foil, of thicknesses between 003 and 0.15 mm has been electroformed at a current density of 30 A/dm2 and an electrolyte temperature of 100°C upon cathodes of surface roughness ranging from 0.04 to 4.4 μm Ra. The surface roughnesses of the face of the foil formed adjacent to the cathode, and of that electrode, are similar. The roughness of the reverse anodic face increases with increasing foil thickness, due to the increase in size of the crystal growth sites. The hardness of the cathodic face of the foil is unaffected by either cathode surface roughness or foil thickness. The hardness of the anodic face increases with both increasing cathode surface roughness and decreasing foil thickness, due to corresponding changes in grain size. A slight net decrease in tensile properties with increasing cathode surface roughness is attributed to the greater amount of stress concentration borne by the rougher foils. Young's modulus for the foil is not affected by cathode surface roughness. The electroforming of foil upon a mandrel surface carrying an isolated V-shaped scratch, 0.14 mm deep and 0.28 mm wide, has also been studied by numerical and experimental methods. The cathodic surface of foil is found to adopt the shape of the scratch whilst its upper side becomes level. The effect upon the geometric configuration of the foil depends upon the relationship between current efficiency and current density for the electrolyte, and on the polarisation (overpotential) characteristics at the mandrel surface.

Sign in / Sign up

Export Citation Format

Share Document