Pulse plated Sn-Cu solder coatings from stannate bath

2019 ◽  
Vol 32 (1) ◽  
pp. 24-32
Author(s):  
Ashutosh Sharma ◽  
Byungmin Ahn
Keyword(s):  
Current Density ◽  
Pulse Plating ◽  
Ratio Measurement ◽  
Content Type ◽  
Composition Control ◽  
Spread Ratio ◽  
Pulse Electroplating ◽  
Key Issues ◽  
Sodium Stannate ◽  
A Current

Purpose The purpose of this paper is to investigate the influence of pulse plating current density on the morphology and solderability of Pb-free Sn-Cu solder coatings prepared from alkaline stannate baths. Design/methodology/approach Sn-Cu solder coatings were produced from a plating solution containing sodium stannate, copper stannate, sodium hydroxide and sorbitol additive on copper substrates. The pulse plating experiments were conducted in galvanostatic mode. The plating current density was varied from 5 to 25 mA/cm2, and the morphology of the coatings was studied. The solderability of the coatings was assessed by spread ratio measurement after reflowing the solder coatings at 250°C. Findings The composition control of eutectic solders is always a challenge in plating. The findings show that Sn-Cu coatings prepared by pulse plating are composed of tetragonal ß-Sn structure and Cu6Sn5 compounds irrespective of bath composition and conditions. The final coatings were very dense and smooth with nodular morphology. It was shown that a eutectic composition can be achieved if we apply a current density of ∼15-20 mA/cm2. The solderability studies suggest that solder coatings plated at and beyond 15 mA/cm2 are more suitable for solder finish applications. Originality/value The work presents key issues in pulse electroplating of Sn-Cu solder coatings from an alkaline bath. Possible strategies to control the eutectic Sn-Cu composition by plating process are recommended.

scholarly journals Pure Sn Coatings Produced by Pulse Plating from Stannate Bath

Coatings ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 117 ◽  
Author(s):  
Sharma ◽  
Seo ◽  
Ahn
Keyword(s):  
Sodium Hydroxide ◽  
Current Density ◽  
Plating Bath ◽  
Cu Substrate ◽  
Spread Ratio ◽  
Current Densities ◽  
Sodium Stannate ◽  
Alkaline Bath ◽  
Pure Sn ◽  
A Current

We have produced pure Sn coatings from an alkaline bath plating. The plating bath was composed of sodium stannate and sodium hydroxide with sorbitol as an additive. The experiments were performed with a potentiostat/galvanostat at various current densities from 5–25 mA/cm2. The morphology of the coatings, thickness, plating rate, and microhardness were evaluated. Furthermore the wetting of the Sn coatings on a Cu substrate was also assessed by area spread ratio measurements after reflow at 250 °C. The resultant coatings were very smooth and shiny. Initially, the plating morphology was uneven and a nodular type, which further improved with increasing current density up to 15 mA/cm2. The plating rate and thickness were the maximum at a current density of 15 mA/cm2. The coatings had higher strength and solderability at 15 mA/cm2 due to the improved microstructure and plating rate.

Facet Topography and Dislocation Structure as a Possible Source for Electrical Heterogeneity in [001] TILT Bicrystals of YBa2Cu3O7-δ

1996 ◽  
Vol 54 ◽  
pp. 338-339
Author(s):  
I-Fei Tsu ◽  
D.L. Kaiser ◽  
S.E. Babcock
Keyword(s):  
Grain Boundary ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Electromagnetic Properties ◽  
Length Scale ◽  
Density Values ◽  
Current Densities ◽  
Applied Fields ◽  
A Current

A current theme in the study of the critical current density behavior of YBa2Cu3O7-δ (YBCO) grain boundaries is that their electromagnetic properties are heterogeneous on various length scales ranging from 10s of microns to ˜ 1 Å. Recently, combined electromagnetic and TEM studies on four flux-grown bicrystals have demonstrated a direct correlation between the length scale of the boundaries’ saw-tooth facet configurations and the apparent length scale of the electrical heterogeneity. In that work, enhanced critical current densities are observed at applied fields where the facet period is commensurate with the spacing of the Abrikosov flux vortices which must be pinned if higher critical current density values are recorded. To understand the microstructural origin of the flux pinning, the grain boundary topography and grain boundary dislocation (GBD) network structure of [001] tilt YBCO bicrystals were studied by TEM and HRTEM.

A highly stable CoMo2S4/Ni3S2 heterojunction electrocatalyst for efficient hydrogen evolution

2021 ◽  
Author(s):  
Minmin Wang ◽  
Mengke Zhang ◽  
Wenwu Song ◽  
Weiting Zhong ◽  
Xunyue Wang ◽  
...  
Keyword(s):  
Hydrogen Evolution ◽  
Current Density ◽  
A Current

A CoMo2S4/Ni3S2 heterojunction is prepared with an overpotential of only 51 mV to drive a current density of 10 mA cm−2 in 1 M KOH solution and ∼100% of the potential remains in the ∼50 h chronopotentiometric curve at 10 mA cm−2.

scholarly journals Investigations, actions and learning from an outbreak of SARS-CoV-2 infection among healthcare workers in the United Kingdom

2020 ◽  
pp. 175717742097679
Author(s):  
Kordo Saeed ◽  
Emanuela Pelosi ◽  
Nitin Mahobia ◽  
Nicola White ◽  
Christopher Labdon ◽  
...  
Keyword(s):  
Real Time ◽  
Healthcare Workers ◽  
Healthcare Facility ◽  
Rt Pcr ◽  
Serum Samples ◽  
The United Kingdom ◽  
Key Issues ◽  
Current Infection ◽  
Polymerase Chain ◽  
A Current

Background: We report an outbreak of SARS coronavirus-2 (SARS-CoV-2) infection among healthcare workers (HCW) in an NHS elective healthcare facility. Methodology: A narrative chronological account of events after declaring an outbreak of SARS-CoV-2 among HCWs. As part of the investigations, HCWs were offered testing during the outbreak. These were: (1) screening by real-time reverse transcriptase polymerase chain reaction (RT- PCR) to detect a current infection; and (2) serum samples to determine seroprevalence. Results: Over 180 HCWs were tested by real-time RT-PCR for SARS-CoV-2 infection. The rate of infection was 15.2% (23.7% for clinical or directly patient-facing HCWs vs. 4.8% in non-clinical non-patient-facing HCWs). Of the infected HCWs, 57% were asymptomatic. Seroprevalence (SARS-CoV-2 IgG) among HCWs was 13%. It was challenging to establish an exact source for the outbreak. The importance of education, training, social distancing and infection prevention practices were emphasised. Additionally, avoidance of unnecessary transfer of patients and minimising cross-site working for staff and early escalation were highlighted. Establishing mass and regular screening for HCWs are also crucial to enabling the best care for patients while maintaining the wellbeing of staff. Conclusion: To our knowledge, this is the first UK outbreak report among HCWs and we hope to have highlighted some key issues and learnings that can be considered by other NHS staff and HCWs globally when dealing with such a task in future.

Real-Time Tem Studies of Electromigration in Submicron Aluminum Runners

1995 ◽  
Vol 391 ◽  
Author(s):  
S. P. Riege ◽  
A. W. Hunt ◽  
J. A. Prybyla
Keyword(s):  
Real Time ◽  
Joule Heating ◽  
Current Density ◽  
Constant Voltage ◽  
Sample Design ◽  
A Current

AbstractDirect real-time observations of electromigration (EM) in submicron Al interconnects were made using a special sample-stage which allowed TEM observations to be recorded while simultaneously heating and passing current through the sample. The samples consisted of 4000 Å thick Al(0.5wt%Cu) patterned over a TEM-transparent window into five runners in parallel, with linewidths 0.2, 0.3, 0.5, 0.8, and 1.0 μm. Both passivated and unpassivated samples were examined. A current density of 2 x 106A/cm2 was used with temperatures ranging from 200 - 350°C. The experiments were done using constant voltage testing, and we used a special sample design which dramatically minimized Joule-heating. Our approach has allowed us to directly observe voids form, grow, migrate, pin, fail a runner, and heal, all with respect to the detailed local microstructure of the runners.

The 2016 Police and Crime Commissioner elections

2017 ◽  
Vol 16 (2) ◽  
pp. 41-54 ◽  
Author(s):  
Peter Joyce
Keyword(s):  
Public Awareness ◽  
Primary Source ◽  
Source Material ◽  
Content Type ◽  
The Public ◽  
The Social ◽  
Key Issues ◽  
The Subject ◽  
The Government

Purpose The purpose of this paper is to analyse the 2016 elections for Police and Crime Commissioners (PCCs) and to compare them with those that took place in 2012. It seeks to evaluate the background of the candidates who stood for office in 2016, the policies that they put forward, the results of the contests and the implications of the 2016 experience for future PCC elections. Design/methodology/approach This paper is based around several key themes – the profile of candidates who stood for election, preparations conducted prior to the contests taking place, the election campaign and issues raised during the contests, the results and the profile of elected candidates. The paper is based upon documentary research, making particular use of primary source material. Findings The research establishes that affiliation to a political party became the main route for successful candidates in 2016 and that local issues related to low-level criminality will dominate the future policing agenda. It establishes that although turnout was higher than in 2012, it remains low and that further consideration needs to be devoted to initiatives to address this for future PCC election contests. Research limitations/implications The research focusses on the 2016 elections and identifies a number of key issues that emerged during the campaign affecting the conduct of the contests which have a bearing on future PCC elections. It treats these elections as a bespoke topic and does not seek to place them within the broader context of the development of the office of PCC. Practical implications The research suggests that in order to boost voter participation in future PCC election contests, PCCs need to consider further means to advertise the importance of the role they perform and that the government should play a larger financial role in funding publicity for these elections and consider changing the method of election. Social implications The rationale for introducing PCCs was to empower the public in each police force area. However, issues that include the enhanced importance of political affiliation as a criteria for election in 2016 and the social unrepresentative nature of those who stood for election and those who secured election to this office in these contests coupled with shortcomings related to public awareness of both the role of PCCs and the timing of election contests threaten to undermine this objective. Originality/value The extensive use of primary source material ensures that the subject matter is original and its interpretation is informed by an academic perspective.

scholarly journals Hysteresis Analysis of Hole-Transport-Material-Free Monolithic Perovskite Solar Cells with Carbon Counter Electrode by Current Density–Voltage and Impedance Spectra Measurements

Nanomaterials ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 48
Author(s):  
Syed Afaq Ali Shah ◽  
Muhammad Hassan Sayyad ◽  
Jinghua Sun ◽  
Zhongyi Guo
Keyword(s):  
Time Delay ◽  
Current Density ◽  
Power Conversion ◽  
Perovskite Solar Cells ◽  
Hole Transport ◽  
Impedance Spectra ◽  
Voltage Measurement ◽  
Sweep Time ◽  
Measurement Protocol ◽  
A Current

Due to the tremendous increase in power conversion efficiency (PCE) of organic–inorganic perovskite solar cells (PSCs), this technology has attracted much attention. Despite being the fastest-growing photovoltaic technology to date, bottlenecks such as current density–voltage (J–V) hysteresis have significantly limited further development. Current density measurements performed with different sweep scan speeds exhibit hysteresis and the photovoltaic parameters extracted from the current density–voltage measurements for both scan directions become questionable. A current density–voltage measurement protocol needs to be established which can be used to achieve reproducible results and to compare devices made in different laboratories. In this work, we report a hysteresis analysis of a hole-transport-material-free (HTM-free) carbon-counter-electrode-based PSC conducted by current density–voltage and impedance spectra measurements. The effect of sweep scan direction and time delay was examined on the J–V characteristics of the device. The hysteresis was observed to be strongly sweep scan direction and time delay dependent and decreased as the delay increased. The J–V analysis conducted in the reverse sweep scan direction at a lower sweep time delay of 0.2 s revealed very large increases in the short circuit current density and the power conversion efficiency of 57.7% and 56.1%, respectively, compared with the values obtained during the forward scan under the same conditions. Impedance spectroscopy (IS) investigations were carried out and the effects of sweep scan speed, time delay, and frequency were analyzed. The hysteresis was observed to be strongly sweep scan direction, sweep time delay, and frequency dependent. The correlation between J–V and IS data is provided. The wealth of photovoltaic and impendence spectroscopic data reported in this work on the hysteresis study of the HTM-free PSC may help in establishing a current density–voltage measurement protocol, identifying components and interfaces causing the hysteresis, and modeling of PSCs, eventually benefiting device performance and long-term stability.

scholarly journals A Hierarchical Architecture of Functionalized Polyaniline/Manganese Dioxide Composite with Stable-Enhanced Electrochemical Performance

2021 ◽  
Vol 5 (5) ◽  
pp. 129
Author(s):  
Yapeng Wang ◽  
Yanxiang Wang ◽  
Chengjuan Wang ◽  
Yongbo Wang
Keyword(s):  
Electrochemical Performance ◽  
Manganese Dioxide ◽  
Specific Capacitance ◽  
Current Density ◽  
Electrode Materials ◽  
High Efficiency ◽  
Scanning Speed ◽  
Hierarchical Architecture ◽  
Electrochemical Window ◽  
A Current

As one of the most outstanding high-efficiency and environmentally friendly energy storage devices, the supercapacitor has received extensive attention across the world. As a member of transition metal oxides widely used in electrode materials, manganese dioxide (MnO2) has a huge development potential due to its excellent theoretical capacitance value and large electrochemical window. In this paper, MnO2 was prepared at different temperatures by a liquid phase precipitation method, and polyaniline/manganese dioxide (PANI/MnO2) composite materials were further prepared in a MnO2 suspension. MnO2 and PANI/MnO2 synthesized at a temperature of 40 °C exhibit the best electrochemical performance. The specific capacitance of the sample MnO2-40 is 254.9 F/g at a scanning speed of 5 mV/s and the specific capacitance is 241.6 F/g at a current density of 1 A/g. The specific capacitance value of the sample PANI/MnO2-40 is 323.7 F/g at a scanning speed of 5 mV/s, and the specific capacitance is 291.7 F/g at a current density of 1 A/g, and both of them are higher than the specific capacitance value of MnO2. This is because the δ-MnO2 synthesized at 40 °C has a layered structure, which has a large specific surface area and can accommodate enough electrolyte ions to participate the electrochemical reaction, thus providing sufficient specific capacitance.

Archiving in the networked world: authenticity and integrity

2012 ◽  
Vol 30 (3) ◽  
pp. 545-552
Author(s):  
Michael Seadle
Keyword(s):  
Design Methodology ◽  
Economic Value ◽  
Digital Environment ◽  
Content Type ◽  
Digital World ◽  
Digital Work ◽  
Mathematical Algorithms ◽  
Key Issues ◽  
Technical Sense

PurposeThis article aims to discuss how concepts from the analog world apply to a purely digital environment, and look in particular at how authenticity needs to be viewed in the digital world in order to make some form of validation possible.Design/methodology/approachThe article describes authenticity and integrity in the analog world and looks at how to measure it in a digital environment.FindingsAuthenticity in the digital world generally means, in a purely technical sense, that a document's integrity has been checked using mathematical algorithms against other copies on independently managed servers, and that provenance records show that the document has a clearly established succession from a clearly defined original. Readers should recognize that this is different than how one defines authenticity and integrity in the analog world.Originality/valueMost of the key issues surrounding digital authenticity have not yet been tested, but they will be when the economic value of an authentic digital work reaches the courts.

Sign in / Sign up

Export Citation Format

Share Document