scholarly journals Study on Electromigration Effects and IMC Formation on Cu–Sn Films Due to Current Stress and Temperature

2020 ◽  
Vol 10 (24) ◽  
pp. 8893
Author(s):  
Zhao-Ying Wang ◽  
Nhat Minh Dang ◽  
Po-Hsun Wang ◽  
Terry Yuan-Fang Chen ◽  
Ming-Tzer Lin
Keyword(s):  
Intermetallic Compound ◽  
Growth Mechanism ◽  
Current Density ◽  
Structural Changes ◽  
Defect Formation ◽  
Copper Substrate ◽  
Signal Delay ◽  
Cross Sectional ◽  
Current Densities

In this study, the effects of electromigration on a solder/copper substrate due to temperature and current density stress were investigated. The copper–tin (Cu–Sn) film samples were subjected under a fixed current and various heating conditions (130 °C and 180 °C) and current densities (different cross-sectional areas). The micro-structural changes and intermetallic compound (IMC) formation were observed, and failure phenomena (brittle cracks, voids, bumps, etc.) on the structures of samples were discussed. The results showed that the IMC thickness increased as the temperature and current density increased. Moreover, it was found that the higher the temperature and current density was, the greater the defects that were observed. By adjusting the designs of sample structures, the stress from the current density can be decreased, resulting in reduced failure phenomena, such as signal delay, distortion, and short circuiting after long-term use of the material components. A detailed IMC growth mechanism and defect formation were also closely studied and discussed.

Electromigration in Solder Joints for High Temperature Flip-Chip Application

2011 ◽  
Vol 2011 (DPC) ◽  
pp. 002481-002506
Author(s):  
Mathias Nowottnick ◽  
Andreas Fix
Keyword(s):  
High Temperature ◽  
Current Density ◽  
Flip Chip ◽  
Solder Joints ◽  
Metallographic Analysis ◽  
Solder Alloys ◽  
Directed Movement ◽  
Cross Sectional ◽  
Current Densities ◽  
And Migration

The electromigration effects in chip metallization and wire bonds are well known and detailed investigated. Current density could be extremely high because of the small size of the cross sectional area of conductors. This can cause a migration of metal atoms toward the electrical field, so current densities up to 106 A/cm2 are possible. In comparison with chip structures are the usual solder joints of flip chips relatively thick. But the homologue temperature of solder alloys, typically based on tin, is also much higher than for gold or aluminum wires. For instance a SAC solder alloy is naturally preheated up to 0.6 homologue temperature, for high temperature application with 125 °C operating temperature even more than 0.8. This means, that atoms are very agile and a directed movement needs only lower field strength. Additionally is the specific resistance of solder alloys tenfold higher than for aluminum, copper or silver. So is the self-heating of solder joints not negligible. This contribution shows the test results of flip-chip assemblies, loaded with different current densities and stored at 125 °C ambient temperature. At the end of life of a significant number of test chips, a metallographic analysis shows the causing failure effects and weak spots of assemblies. Accompanying simulations help to explain the interaction between current density and migration effects.

scholarly journals Boride-derived oxygen-evolution catalysts

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ning Wang ◽  
Aoni Xu ◽  
Pengfei Ou ◽  
Sung-Fu Hung ◽  
Adnan Ozden ◽  
...  
Keyword(s):  
Oxygen Evolution ◽  
Current Density ◽  
Membrane Electrode Assembly ◽  
Membrane Electrode ◽  
Long Term Stability ◽  
Metal Borides ◽  
Current Densities ◽  
Alkaline Membrane ◽  
Co Reduction

AbstractMetal borides/borates have been considered promising as oxygen evolution reaction catalysts; however, to date, there is a dearth of evidence of long-term stability at practical current densities. Here we report a phase composition modulation approach to fabricate effective borides/borates-based catalysts. We find that metal borides in-situ formed metal borates are responsible for their high activity. This knowledge prompts us to synthesize NiFe-Boride, and to use it as a templating precursor to form an active NiFe-Borate catalyst. This boride-derived oxide catalyzes oxygen evolution with an overpotential of 167 mV at 10 mA/cm2 in 1 M KOH electrolyte and requires a record-low overpotential of 460 mV to maintain water splitting performance for over 400 h at current density of 1 A/cm2. We couple the catalyst with CO reduction in an alkaline membrane electrode assembly electrolyser, reporting stable C2H4 electrosynthesis at current density 200 mA/cm2 for over 80 h.

Effects of the Additives and Current Density on the Electrodeposition Behavior and Mechanical Properties of the Ni-SiC Composite Coatings

2007 ◽  
Vol 345-346 ◽  
pp. 1533-1536 ◽  
Author(s):  
Teck Su Oh ◽  
Jae Ho Lee ◽  
Ji Young Byun ◽  
Tae Sung Oh
Keyword(s):  
Mechanical Properties ◽  
Sulfuric Acid ◽  
Composite Coating ◽  
Surface Properties ◽  
Current Density ◽  
Composite Coatings ◽  
Cross Sectional ◽  
Sic Particles ◽  
Current Densities ◽  
Sulfamate Bath

In Ni-SiC composite coating, the SiC content is dependent on the surface properties of SiC particles. As sulfuric acid has a strong dehydration force, addition of sulfuric acid in the Ni sulfamate bath changed the surface properties of SiC particles, affecting the codeposition behavior of SiC particles. Also the additives such as SDS affect the electrodeposition behavior of the Ni-SiC composite coating. In this study, effects of the HSO4 ‾ and the current density on the electrodeposition behavior of the Ni-SiC composite coating have been investigated. The Ni-SiC composite coatings were electrodeposited at current densities of 50~200mA/cm2. The surface and cross-sectional morphologies of the Ni-SiC composite coatings were observed using SEM, and their mechanical properties were characterized with micro-Vikers hardness.

scholarly journals Alcohols electrooxidation coupled with H2 production at high current densities promoted by a cooperative catalyst

2022 ◽  
Vol 13 (1) ◽  
Author(s):  
Zhenhua Li ◽  
Yifan Yan ◽  
Si-Min Xu ◽  
Hua Zhou ◽  
Ming Xu ◽  
...  
Keyword(s):  
Benzyl Alcohol ◽  
Current Density ◽  
High Current Density ◽  
H2 Production ◽  
Open Circuit ◽  
High Current ◽  
Cell Potential ◽  
Current Densities ◽  
Electrode Membrane

AbstractElectrochemical alcohols oxidation offers a promising approach to produce valuable chemicals and facilitate coupled H2 production. However, the corresponding current density is very low at moderate cell potential that substantially limits the overall productivity. Here we report the electrooxidation of benzyl alcohol coupled with H2 production at high current density (540 mA cm−2 at 1.5 V vs. RHE) over a cooperative catalyst of Au nanoparticles supported on cobalt oxyhydroxide nanosheets (Au/CoOOH). The absolute current can further reach 4.8 A at 2.0 V in a more realistic two-electrode membrane-free flow electrolyzer. Experimental combined with theoretical results indicate that the benzyl alcohol can be enriched at Au/CoOOH interface and oxidized by the electrophilic oxygen species (OH*) generated on CoOOH, leading to higher activity than pure Au. Based on the finding that the catalyst can be reversibly oxidized/reduced at anodic potential/open circuit, we design an intermittent potential (IP) strategy for long-term alcohol electrooxidation that achieves high current density (>250 mA cm−2) over 24 h with promoted productivity and decreased energy consumption.

scholarly journals Cognitive and brain structural changes in long-term oligodendroglial tumor survivors

2019 ◽  
Vol 21 (11) ◽  
pp. 1470-1479 ◽  
Author(s):  
Nuria Cayuela ◽  
Esteban Jaramillo-Jiménez ◽  
Estela Càmara ◽  
Carles Majós ◽  
Noemi Vidal ◽  
...  
Keyword(s):  
Cognitive Impairment ◽  
Structural Changes ◽  
Volumetric Analysis ◽  
World Health ◽  
Cross Sectional ◽  
Oligodendroglial Tumor ◽  
Group 3 ◽  
Group 2 ◽  
Group 1

Abstract Background We identify cognitive impairment and MRI structural brain changes in long-term oligodendroglial tumor survivors treated with radiation therapy (RT) alone (21%) or with chemotherapy (CT) (79%). Methods Oligodendroglial tumor patients (based on the World Health Organization [WHO] 2007 classification) who completed RT ± CT at least 2 years before the study initiation, were classified into 3 groups according to the time treatment was completed: Group 1 = 2–5 years (n = 22), Group 2 = 6–10 years (n = 13), and Group 3 >10 years (n = 13). All patients had a cross-sectional neuropsychological evaluation (n = 48) and a longitudinal volumetric analysis (gray matter [GM; n = 34]) between postsurgical and last follow-up MRI. White matter (WM) changes on MRI were assessed using a qualitative scale. Results There were no differences regarding tumor or treatment-related characteristics between groups. Six of 22 patients (27.3%) in Group 1; 5/13 (38.5%) in Group 2; and 9/13 (69.2%) in Group 3 had cognitive impairment that was considered severe in 3/22 patients (13.6%) in Group 1; 4/13 (30.8%) in Group 2; and 6/13 (46.2%) in Group 3. Patients in Groups 2 and 3 showed significant GM atrophy and more leukoencephalopathy than Group 1. Cognitive deficits were associated with brain atrophy and WM changes. Conclusions Long-term oligodendroglial tumor survivors who underwent standard RT ± CT treatment, mainly >5 years of its completion, present cognitive impairment, especially on memory and executive functions, associated with late GM and WM damage, thus highlighting the need of developing future strategies in patients with oligodendroglial tumor and long expected survival.

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.

Electron-beam damage of oxides at high current densities

1989 ◽  
Vol 47 ◽  
pp. 634-635
Author(s):  
M. R. McCartney ◽  
J. K. Weiss ◽  
David J. Smith
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Current Density ◽  
Transition Metal Oxides ◽  
Time Resolved ◽  
Rapid Acquisition ◽  
Resolution Electron ◽  
Current Densities ◽  
Electron Stimulated Desorption ◽  
Channel Analyzer

It is well-known that electron-beam irradiation within the electron microscope can induce a variety of surface reactions. In the particular case of maximally-valent transition-metal oxides (TMO), which are susceptible to electron-stimulated desorption (ESD) of oxygen, it is apparent that the final reduced product depends, amongst other things, upon the ionicity of the original oxide, the energy and current density of the incident electrons, and the residual microscope vacuum. For example, when TMO are irradiated in a high-resolution electron microscope (HREM) at current densities of 5-50 A/cm2, epitaxial layers of the monoxide phase are found. In contrast, when these oxides are exposed to the extreme current density probe of an EM equipped with a field emission gun (FEG), the irradiated area has been reported to develop either holes or regions almost completely depleted of oxygen. ’ In this paper, we describe the responses of three TMO (WO3, V2O5 and TiO2) when irradiated by the focussed probe of a Philips 400ST FEG TEM, also equipped with a Gatan 666 Parallel Electron Energy Loss Spectrometer (P-EELS). The multi-channel analyzer of the spectrometer was modified to take advantage of the extremely rapid acquisition capabilities of the P-EELS to obtain time-resolved spectra of the oxides during the irradiation period. After irradiation, the specimens were immediately removed to a JEM-4000EX HREM for imaging of the damaged regions.

Theoretical and Methodological Problems of a 10-Year Follow-Up Program Evaluation Study

2002 ◽  
Vol 18 (3) ◽  
pp. 229-241 ◽  
Author(s):  
Kurt A. Heller ◽  
Ralph Reimann
Keyword(s):  
Program Evaluation ◽  
Evaluation Studies ◽  
Evaluation Study ◽  
Control Groups ◽  
Cross Sectional ◽  
Long Term Study ◽  
Partial Inclusion ◽  
Methodological Problems

Summary In this paper, conceptual and methodological problems of school program evaluation are discussed. The data were collected in conjunction with a 10 year cross-sectional/longitudinal investigation with partial inclusion of control groups. The experiences and conclusions resulting from this long-term study are revealing not only from the vantage point of the scientific evaluation of new scholastic models, but are also valuable for program evaluation studies in general, particularly in the field of gifted education.

Coming Together Through Falling Apart

2019 ◽  
Vol 40 (2) ◽  
pp. 151-168
Author(s):  
Heather Churchill ◽  
Jeremy M. Ridenour
Keyword(s):  
Data Analysis ◽  
Qualitative Data ◽  
Structural Changes ◽  
Systematic Approach ◽  
Qualitative Approach ◽  
Psychological Assessments ◽  
Transference And Countertransference ◽  
Testing Data ◽  
Psychoanalytically Oriented Psychotherapy

Abstract. Assessing change during long-term psychotherapy can be a challenging and uncertain task. Psychological assessments can be a valuable tool and can offer a perspective from outside the therapy dyad, independent of the powerful and distorting influences of transference and countertransference. Subtle structural changes that may not yet have manifested behaviorally can also be assessed. However, it can be difficult to find a balance between a rigorous, systematic approach to data, while also allowing for the richness of the patient’s internal world to emerge. In this article, the authors discuss a primarily qualitative approach to the data and demonstrate the ways in which this kind of approach can deepen the understanding of the more subtle or complex changes a particular patient is undergoing while in treatment, as well as provide more detail about the nature of an individual’s internal world. The authors also outline several developmental frameworks that focus on the ways a patient constructs their reality and can guide the interpretation of qualitative data. The authors then analyze testing data from a patient in long-term psychoanalytically oriented psychotherapy in order to demonstrate an approach to data analysis and to show an example of how change can unfold over long-term treatments.

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