The Experts below are selected from a list of 351 Experts worldwide ranked by ideXlab platform
Jonghyun Lee - One of the best experts on this subject based on the ideXlab platform.
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die Sinter Bonding in air using cu ag particulate preform and rapid formation of near full density bondline
Journal of materials research and technology, 2021Co-Authors: Myeong In Kim, Jonghyun LeeAbstract:Abstract Pressure-assisted Sinter Bonding between an Ag-finished die and an Ag-finished substrate was performed in air using an Ag-coated Cu (Cu@Ag) particulate preform to rapidly achieve a bondline with high-temperature sustainability, low-defect structure, and high thermal conductivity. The preform was prepared as a binder-free material by pelletizing 351 nm Cu@Ag particles with 20 wt.% Ag shells. At 350 °C and at pressures of 5 MPa and 10 MPa, the Bonding exhibited shear strength values approaching 20 and 24 MPa, respectively, just after 30 s and the pressure increase to 10 MPa accelerated the increase in strength with increasing Bonding time. Furthermore, a bondline with a near-full density structure was formed immediately after Bonding for only 30 s. The fast Sinter Bonding and near-full density formation are mainly attributed to the initial strong contact between the particles and the particle rearrangement behavior by the sliding deformation of Sintered Ag after dewetting of the Ag shells on the Cu core particles during the pressure-assisted Bonding.
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die Sinter Bonding in air using copper formate preform for formation of full density bondline
Transactions of Nonferrous Metals Society of China, 2021Co-Authors: Yunju Lee, Jonghyun LeeAbstract:Abstract Pressure-assisted Sinter Bonding was performed in air at 250−350 °C using a preform comprising copper formate particles to form a bondline that is sustainable at high temperatures. H2 and CO generated concurrently by the pyrolysis of copper formate at 210 °C during the Sinter Bonding removed the native oxide and other oxides grown on bulk Cu finishes, enabling interface Bonding. Moreover, Cu produced in situ by the reduction of Cu(II) accelerated the Sinter Bonding. Consequently, the Bonding achieved at 300−350 °C under 5 MPa exhibited sufficient shear strength of 20.0−31.5 MPa after 180−300 min of Sinter Bonding. In addition, an increase in pressure to 10 MPa resulted in shear strength of 21.9 MPa after an extremely short time of 30 s at 250 °C, and a near-full-density bondline was achieved after 300 s. The obtained results indicate the promising potential of the preform comprising copper formate particles for high-speed Sinter Bonding.
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pressure assisted Sinter Bonding method at 300 c in air using a resin free paste containing 1 5 μm cu ag particles
Applied Surface Science, 2021Co-Authors: Eun Byeol Choi, Jonghyun LeeAbstract:Abstract Pressure-assisted Sinter Bonding was conducted in air through in-situ Ag shells dewetting of 1.5 μm Ag-coated Cu particles during die attachment for power devices. The effects on Bonding when adding a solvent in the prepared paste were addressed. The dewetting-formed Ag nano-nodules induced faster Ag–Ag Sintering. Furthermore, the Bonding strength in the die was enhanced by the progress of out-diffused Cu–Cu Sintering after dewetting. The reducibility of the solvent had a significant effect on the progress of Cu–Cu Sintering. The Bonding pressure and temperature were 5 MPa and 300 °C, respectively, and the resulting die exhibited an average shear strength of 22.7 MPa with a polyol-based solvent providing high reducibility.
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effect of compression pressure on strength of low temperature Sinter Bonding produced using silver formate
Powder Metallurgy, 2021Co-Authors: Yunju Lee, Jonghyun LeeAbstract:Novel pressure-assisted Sinter Bonding at 200°C using silver (Ag) formate particles was performed in air using an Ag-finished die and substrate to achieve a reliable Ag bondline even at high temper...
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improved Sinter Bonding properties of silver coated copper flake paste in air by the addition of sub micrometer silver coated copper particles
Journal of materials research and technology, 2020Co-Authors: Myeong In Kim, Eun Byeol Choi, Jonghyun LeeAbstract:Abstract To promptly form a bondline with high thermal stability and thermal conductivity using a small amount of expensive Ag, dies were attached to Ag finishes by pressure-assisted Sinter Bonding at 300 °C using micrometer-sized Ag-coated Cu (Cu@Ag) flakes. Small Cu@Ag particles of 350 nm size were also added to the paste to increase the Sinterability by increasing the contact points, which resulted in a bimodal paste. The dewetting of the Ag shells in Cu@Ag induced initial Sintering, and the rearrangement of the 350 nm Cu@Ag particles as well as the bending of the Cu@Ag flakes under pressure effectively filled the voids between the particles. As a result, shear strengths of almost 20 MPa and 28.9 MPa were obtained after only 1 and 5 min of Sinter Bonding, respectively. In addition, a bondline with a unique near full density microstructure was achieved in the 5 min Sinter-bonded sample.
Nathan A. S. Webster - One of the best experts on this subject based on the ideXlab platform.
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Fundamentals of Silico-Ferrite of Calcium and Aluminum (SFCA) and SFCA-I Iron Ore Sinter Bonding Phase Formation: Effects of MgO on Phase Formation During Heating
JOM, 2020Co-Authors: Nathan A. S. Webster, Rachel Pattel, James R. Manuel, Mark I Pownceby, Justin A. KimptonAbstract:The effect of MgO on the stability, concentrations and formation mechanisms of silico-ferrite of calcium and aluminum (SFCA and SFCA-I) iron ore Sinter Bonding phases during heating in synthetic mixtures was investigated using in situ x-ray diffraction. The novelty of this study is in the intricate detail in which the formation mechanisms of the SFCA-I and SFCA phases are characterized, and the observation of the effects of MgO addition on intermediate phases. For example, the significant mechanistic effect of increasing MgO content is the lack of additional SFCA formed after SFCA-I decomposition, with additional magnesioferrite spinel being formed instead. In MgO-free mixtures, the decomposition of SFCA-I typically results in a significant increase in SFCA concentration. Through the results of phase equilibria experiments, this study also provides evidence that the SFCA-I structure accommodates more Mg^2+ than the SFCA structure, which is consistent with evidence that the SFCA-I structure contains a higher amount of Fe^2+ than SFCA.
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fundamentals of silico ferrite of calcium and aluminium sfca and sfca i iron ore Sinter Bonding phase formation effects of mill scale addition
Powder Diffraction, 2017Co-Authors: Nathan A. S. Webster, Mark I Pownceby, Rachel PattelAbstract:The thermal decomposition of mill scale, and the effect of mill scale addition on the formation and decomposition of Silico-Ferrite of Calcium and Aluminium (SFCA) and SFCA-I iron ore Sinter Bonding phases, has been investigated using in situ X-ray diffraction. Application of the external standard method of quantitative phase analysis of the in situ data collected during decomposition of the mill scale highlighted the applicability of this method for the determination of the nature and abundance of amorphous material in a mineral sample. Increasing mill scale addition from 2.6 to 10.6 and to 21.2 wt% in an otherwise synthetic Sinter mixture composition designed to form SFCA did not significantly affect the thermal stability ranges of SFCA-I or SFCA, nor did it significantly affect the amount of each of SFCA or SFCA-I, which formed. This was attributed to the low impurity (i.e. Mn, Mg) concentration in the mill scale, and also the transformation to hematite during heating of the wustite and magnetite present in the mill scale, with the hematite available for reaction to form SFCA and SFCA-I.
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Fundamentals of Silico-Ferrite of Calcium and Aluminum (SFCA) and SFCA-I Iron Ore Sinter Bonding Phase Formation: Effects of CaO:SiO_2 Ratio
Metallurgical and Materials Transactions B, 2014Co-Authors: Nathan A. S. Webster, Ian C. Madsen, Anthony J Studer, James R. Manuel, Mark I Pownceby, Justin A. KimptonAbstract:Effects of basicity, B (CaO:SiO_2 ratio) on the thermal range, concentration, and formation mechanisms of silico-ferrite of calcium and aluminum (SFCA) and SFCA-I iron ore Sinter Bonding phases have been investigated using an in situ synchrotron X-ray diffraction-based methodology with subsequent Rietveld refinement-based quantitative phase analysis. SFCA and SFCA-I phases are the key Bonding materials in iron ore Sinter, and improved understanding of the effects of processing parameters such as basicity on their formation and decomposition may assist in improving efficiency of industrial iron ore Sintering operations. Increasing basicity significantly increased the thermal range of SFCA-I, from 1363 K to 1533 K (1090 °C to 1260 °C) for a mixture with B = 2.48, to ~1339 K to 1535 K (1066 °C to 1262 °C) for a mixture with B = 3.96, and to ~1323 K to 1593 K (1050 °C to 1320 °C) at B = 4.94. Increasing basicity also increased the amount of SFCA-I formed, from 18 wt pct for the mixture with B = 2.48 to 25 wt pct for the B = 4.94 mixture. Higher basicity of the starting Sinter mixture will, therefore, increase the amount of SFCA-I, considered to be more desirable of the two phases. Basicity did not appear to significantly influence the formation mechanism of SFCA-I. It did, however, affect the formation mechanism of SFCA, with the decomposition of SFCA-I coinciding with the formation of a significant amount of additional SFCA in the B = 2.48 and 3.96 mixtures but only a minor amount in the highest basicity mixture. In situ neutron diffraction enabled characterization of the behavior of magnetite after melting of SFCA produced a magnetite plus melt phase assemblage.
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in situ diffraction studies of iron ore Sinter Bonding phase formation qpa considerations and pushing the limits of laboratory data collection
Powder Diffraction, 2014Co-Authors: Nathan A. S. Webster, Ian C. Madsen, Anthony J Studer, Mark I Pownceby, Justin A. KimptonAbstract:The formation and decomposition of silico-ferrite of calcium and aluminium (SFCA) and SFCA-I iron ore Sinter Bonding phases have been investigated using in situ synchrotron and laboratory X-ray diffraction (XRD) and neutron diffraction (ND). An external standard approach for determining absolute phase concentrations via Rietveld refinement-based quantitative phase analysis is discussed. The complementarity of in situ XRD and ND in characterising Sinter phase formation and decomposition is also shown, with the volume diffraction afforded by the neutron technique reducing errors in the quantification of magnetite above ~1200 °C. Finally, by collecting 6 s laboratory XRD datasets and using a heating rate of 175 °C min −1 , phase formation and decomposition have been monitored under heating rates more closely approximating those encountered in industrial iron ore Sintering.
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effect of oxygen partial pressure on the formation mechanisms of complex ca rich ferrites
Isij International, 2013Co-Authors: Ian C. Madsen, Nathan A. S. Webster, Mark I Pownceby, Justin A. KimptonAbstract:The formation mechanisms of the complex Ca-rich ferrite iron ore Sinter Bonding phases SFCA and SFCA-I, during heating of a synthetic Sinter mixture in the range 298–1 623 K and at pO2 = 0.21, 5 × 10 –3 and 1 × 10 –4 atm, were determined using in situ X-ray diffraction. SFCA and, in particular, SFCA-I are desirable Bonding phases in iron ore Sinter, and improved understanding of the effect of parameters such as pO2 on their formation may lead to improved ability to maximise their formation in industrial Sintering processes. SFCA-I and SFCA were both observed to form at pO2 = 0.21 and 5 × 10 –3 atm, with the formation of SFCA-I preceding SFCA formation in each case, but via distinctly different mechanisms at each pO2. No SFCA-I was observed at pO2 = 1 × 10 –4 atm; instead, a Ca-rich phase designated CFAlSi, formed at 1 420 K. By 1 456 K, CFAlSi had decomposed to form melt and a small amount of SFCA. Such a low pO2 during heating of industrial Sinter mixtures is, therefore, undesirable, since it would not result in the formation of an abundance of SFCA and SFCA-I Bonding phases. In addition, CFA phase, which was determined by Webster et al. (Metall. Mater. Trans. B, 43(2012), 1344) to be a key precursor phase in the formation of SFCA at pO2 = 5 × 10 –3 atm, was also observed to form at pO2 = 0.21 and 1 × 10 –4 atm, with the amount decreasing with increasing pO2.
Justin A. Kimpton - One of the best experts on this subject based on the ideXlab platform.
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Fundamentals of Silico-Ferrite of Calcium and Aluminum (SFCA) and SFCA-I Iron Ore Sinter Bonding Phase Formation: Effects of MgO on Phase Formation During Heating
JOM, 2020Co-Authors: Nathan A. S. Webster, Rachel Pattel, James R. Manuel, Mark I Pownceby, Justin A. KimptonAbstract:The effect of MgO on the stability, concentrations and formation mechanisms of silico-ferrite of calcium and aluminum (SFCA and SFCA-I) iron ore Sinter Bonding phases during heating in synthetic mixtures was investigated using in situ x-ray diffraction. The novelty of this study is in the intricate detail in which the formation mechanisms of the SFCA-I and SFCA phases are characterized, and the observation of the effects of MgO addition on intermediate phases. For example, the significant mechanistic effect of increasing MgO content is the lack of additional SFCA formed after SFCA-I decomposition, with additional magnesioferrite spinel being formed instead. In MgO-free mixtures, the decomposition of SFCA-I typically results in a significant increase in SFCA concentration. Through the results of phase equilibria experiments, this study also provides evidence that the SFCA-I structure accommodates more Mg^2+ than the SFCA structure, which is consistent with evidence that the SFCA-I structure contains a higher amount of Fe^2+ than SFCA.
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Fundamentals of Silico-Ferrite of Calcium and Aluminum (SFCA) and SFCA-I Iron Ore Sinter Bonding Phase Formation: Effects of CaO:SiO2 Ratio
'Springer Science and Business Media LLC', 2016Co-Authors: Webster Nas, Mi Pownceby, Ic Madsen, Aj Studer, Justin A. KimptonAbstract:Effects of basicity, B (CaO:SiO2 ratio) on the thermal range, concentration, and formation mechanisms of silico-ferrite of calcium and aluminum (SFCA) and SFCA-I iron ore Sinter Bonding phases have been investigated using an in situ synchrotron X-ray diffraction-based methodology with subsequent Rietveld refinement-based quantitative phase analysis. SFCA and SFCA-I phases are the key Bonding materials in iron ore Sinter, and improved understanding of the effects of processing parameters such as basicity on their formation and decomposition may assist in improving efficiency of industrial iron ore Sintering operations. Increasing basicity significantly increased the thermal range of SFCA-I, from 1363 K to 1533 K (1090 °C to 1260 °C) for a mixture with B = 2.48, to ~1339 K to 1535 K (1066 °C to 1262 °C) for a mixture with B = 3.96, and to ~1323 K to 1593 K (1050 °C to 1320 °C) at B = 4.94. Increasing basicity also increased the amount of SFCA-I formed, from 18 wt pct for the mixture with B = 2.48 to 25 wt pct for the B = 4.94 mixture. Higher basicity of the starting Sinter mixture will, therefore, increase the amount of SFCA-I, considered to be more desirable of the two phases. Basicity did not appear to significantly influence the formation mechanism of SFCA-I. It did, however, affect the formation mechanism of SFCA, with the decomposition of SFCA-I coinciding with the formation of a significant amount of additional SFCA in the B = 2.48 and 3.96 mixtures but only a minor amount in the highest basicity mixture. In situ neutron diffraction enabled characterization of the behavior of magnetite after melting of SFCA produced a magnetite plus melt phase assemblage. © 2014, The Minerals, Metals & Materials Society and ASM International
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Fundamentals of Silico-Ferrite of Calcium and Aluminum (SFCA) and SFCA-I Iron Ore Sinter Bonding Phase Formation: Effects of CaO:SiO_2 Ratio
Metallurgical and Materials Transactions B, 2014Co-Authors: Nathan A. S. Webster, Ian C. Madsen, Anthony J Studer, James R. Manuel, Mark I Pownceby, Justin A. KimptonAbstract:Effects of basicity, B (CaO:SiO_2 ratio) on the thermal range, concentration, and formation mechanisms of silico-ferrite of calcium and aluminum (SFCA) and SFCA-I iron ore Sinter Bonding phases have been investigated using an in situ synchrotron X-ray diffraction-based methodology with subsequent Rietveld refinement-based quantitative phase analysis. SFCA and SFCA-I phases are the key Bonding materials in iron ore Sinter, and improved understanding of the effects of processing parameters such as basicity on their formation and decomposition may assist in improving efficiency of industrial iron ore Sintering operations. Increasing basicity significantly increased the thermal range of SFCA-I, from 1363 K to 1533 K (1090 °C to 1260 °C) for a mixture with B = 2.48, to ~1339 K to 1535 K (1066 °C to 1262 °C) for a mixture with B = 3.96, and to ~1323 K to 1593 K (1050 °C to 1320 °C) at B = 4.94. Increasing basicity also increased the amount of SFCA-I formed, from 18 wt pct for the mixture with B = 2.48 to 25 wt pct for the B = 4.94 mixture. Higher basicity of the starting Sinter mixture will, therefore, increase the amount of SFCA-I, considered to be more desirable of the two phases. Basicity did not appear to significantly influence the formation mechanism of SFCA-I. It did, however, affect the formation mechanism of SFCA, with the decomposition of SFCA-I coinciding with the formation of a significant amount of additional SFCA in the B = 2.48 and 3.96 mixtures but only a minor amount in the highest basicity mixture. In situ neutron diffraction enabled characterization of the behavior of magnetite after melting of SFCA produced a magnetite plus melt phase assemblage.
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in situ diffraction studies of iron ore Sinter Bonding phase formation qpa considerations and pushing the limits of laboratory data collection
Powder Diffraction, 2014Co-Authors: Nathan A. S. Webster, Ian C. Madsen, Anthony J Studer, Mark I Pownceby, Justin A. KimptonAbstract:The formation and decomposition of silico-ferrite of calcium and aluminium (SFCA) and SFCA-I iron ore Sinter Bonding phases have been investigated using in situ synchrotron and laboratory X-ray diffraction (XRD) and neutron diffraction (ND). An external standard approach for determining absolute phase concentrations via Rietveld refinement-based quantitative phase analysis is discussed. The complementarity of in situ XRD and ND in characterising Sinter phase formation and decomposition is also shown, with the volume diffraction afforded by the neutron technique reducing errors in the quantification of magnetite above ~1200 °C. Finally, by collecting 6 s laboratory XRD datasets and using a heating rate of 175 °C min −1 , phase formation and decomposition have been monitored under heating rates more closely approximating those encountered in industrial iron ore Sintering.
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effect of oxygen partial pressure on the formation mechanisms of complex ca rich ferrites
Isij International, 2013Co-Authors: Ian C. Madsen, Nathan A. S. Webster, Mark I Pownceby, Justin A. KimptonAbstract:The formation mechanisms of the complex Ca-rich ferrite iron ore Sinter Bonding phases SFCA and SFCA-I, during heating of a synthetic Sinter mixture in the range 298–1 623 K and at pO2 = 0.21, 5 × 10 –3 and 1 × 10 –4 atm, were determined using in situ X-ray diffraction. SFCA and, in particular, SFCA-I are desirable Bonding phases in iron ore Sinter, and improved understanding of the effect of parameters such as pO2 on their formation may lead to improved ability to maximise their formation in industrial Sintering processes. SFCA-I and SFCA were both observed to form at pO2 = 0.21 and 5 × 10 –3 atm, with the formation of SFCA-I preceding SFCA formation in each case, but via distinctly different mechanisms at each pO2. No SFCA-I was observed at pO2 = 1 × 10 –4 atm; instead, a Ca-rich phase designated CFAlSi, formed at 1 420 K. By 1 456 K, CFAlSi had decomposed to form melt and a small amount of SFCA. Such a low pO2 during heating of industrial Sinter mixtures is, therefore, undesirable, since it would not result in the formation of an abundance of SFCA and SFCA-I Bonding phases. In addition, CFA phase, which was determined by Webster et al. (Metall. Mater. Trans. B, 43(2012), 1344) to be a key precursor phase in the formation of SFCA at pO2 = 5 × 10 –3 atm, was also observed to form at pO2 = 0.21 and 1 × 10 –4 atm, with the amount decreasing with increasing pO2.
Myeong In Kim - One of the best experts on this subject based on the ideXlab platform.
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die Sinter Bonding in air using cu ag particulate preform and rapid formation of near full density bondline
Journal of materials research and technology, 2021Co-Authors: Myeong In Kim, Jonghyun LeeAbstract:Abstract Pressure-assisted Sinter Bonding between an Ag-finished die and an Ag-finished substrate was performed in air using an Ag-coated Cu (Cu@Ag) particulate preform to rapidly achieve a bondline with high-temperature sustainability, low-defect structure, and high thermal conductivity. The preform was prepared as a binder-free material by pelletizing 351 nm Cu@Ag particles with 20 wt.% Ag shells. At 350 °C and at pressures of 5 MPa and 10 MPa, the Bonding exhibited shear strength values approaching 20 and 24 MPa, respectively, just after 30 s and the pressure increase to 10 MPa accelerated the increase in strength with increasing Bonding time. Furthermore, a bondline with a near-full density structure was formed immediately after Bonding for only 30 s. The fast Sinter Bonding and near-full density formation are mainly attributed to the initial strong contact between the particles and the particle rearrangement behavior by the sliding deformation of Sintered Ag after dewetting of the Ag shells on the Cu core particles during the pressure-assisted Bonding.
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improved Sinter Bonding properties of silver coated copper flake paste in air by the addition of sub micrometer silver coated copper particles
Journal of materials research and technology, 2020Co-Authors: Myeong In Kim, Eun Byeol Choi, Jonghyun LeeAbstract:Abstract To promptly form a bondline with high thermal stability and thermal conductivity using a small amount of expensive Ag, dies were attached to Ag finishes by pressure-assisted Sinter Bonding at 300 °C using micrometer-sized Ag-coated Cu (Cu@Ag) flakes. Small Cu@Ag particles of 350 nm size were also added to the paste to increase the Sinterability by increasing the contact points, which resulted in a bimodal paste. The dewetting of the Ag shells in Cu@Ag induced initial Sintering, and the rearrangement of the 350 nm Cu@Ag particles as well as the bending of the Cu@Ag flakes under pressure effectively filled the voids between the particles. As a result, shear strengths of almost 20 MPa and 28.9 MPa were obtained after only 1 and 5 min of Sinter Bonding, respectively. In addition, a bondline with a unique near full density microstructure was achieved in the 5 min Sinter-bonded sample.
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Sinter Bonding and formation of a near full density bondline at 250 c via addition of submicrometer cu particles to micrometer ag coated cu particles
Journal of Materials Science: Materials in Electronics, 2020Co-Authors: Sung Yoon Kim, Myeong In Kim, Jonghyun LeeAbstract:Pressure-assisted die Bonding at 250 °C in air using a paste containing 2 µm Ag-coated Cu particles (Cu@Ag) and 350 nm Cu particles was demonstrated for power device Bonding. At a Cu@Ag-to-Cu mixing ratio of 6:4, the Sinter-bonded dies showed a considerable average shear strength that approached 25 MPa after only 5 min of Bonding. Furthermore, a near-full-density bondline and excellent strength, greater than 30 MPa, were achieved after only 10 min. The remarkably rapid improvement in the strength and microstructure was attributed to the generation of pure Cu nanoparticles on the Cu surfaces by in situ reduction during heating for the Bonding.
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Pressure-Assisted Sinter-Bonding Characteristics at 250 °C in Air Using Bimodal Ag-Coated Cu Particles
Electronic Materials Letters, 2020Co-Authors: Sung Yoon Kim, Myeong In Kim, Jonghyun LeeAbstract:To achieve bondlines with improved heat resistance and thermal conductance during operation, pressure-assisted Sinter-Bonding was performed in air with bimodal Ag-coated Cu particles for die attachment of the next-generation power devices composed of SiC. The Bonding temperature and pressure were 250 °C and 10 MPa, respectively, and the sizes of the bimodal particles were 2 µm and 350 nm. After a short Bonding time of 10 min, a paste with a 6:4 mixing ratio showed an average shear strength of > 20 MPa. The dewetting of Ag shells on the particles and void filling by the 350 nm particles induced rapid Sintering. Graphic Abstract
Mark I Pownceby - One of the best experts on this subject based on the ideXlab platform.
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Fundamentals of Silico-Ferrite of Calcium and Aluminum (SFCA) and SFCA-I Iron Ore Sinter Bonding Phase Formation: Effects of MgO on Phase Formation During Heating
JOM, 2020Co-Authors: Nathan A. S. Webster, Rachel Pattel, James R. Manuel, Mark I Pownceby, Justin A. KimptonAbstract:The effect of MgO on the stability, concentrations and formation mechanisms of silico-ferrite of calcium and aluminum (SFCA and SFCA-I) iron ore Sinter Bonding phases during heating in synthetic mixtures was investigated using in situ x-ray diffraction. The novelty of this study is in the intricate detail in which the formation mechanisms of the SFCA-I and SFCA phases are characterized, and the observation of the effects of MgO addition on intermediate phases. For example, the significant mechanistic effect of increasing MgO content is the lack of additional SFCA formed after SFCA-I decomposition, with additional magnesioferrite spinel being formed instead. In MgO-free mixtures, the decomposition of SFCA-I typically results in a significant increase in SFCA concentration. Through the results of phase equilibria experiments, this study also provides evidence that the SFCA-I structure accommodates more Mg^2+ than the SFCA structure, which is consistent with evidence that the SFCA-I structure contains a higher amount of Fe^2+ than SFCA.
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fundamentals of silico ferrite of calcium and aluminium sfca and sfca i iron ore Sinter Bonding phase formation effects of mill scale addition
Powder Diffraction, 2017Co-Authors: Nathan A. S. Webster, Mark I Pownceby, Rachel PattelAbstract:The thermal decomposition of mill scale, and the effect of mill scale addition on the formation and decomposition of Silico-Ferrite of Calcium and Aluminium (SFCA) and SFCA-I iron ore Sinter Bonding phases, has been investigated using in situ X-ray diffraction. Application of the external standard method of quantitative phase analysis of the in situ data collected during decomposition of the mill scale highlighted the applicability of this method for the determination of the nature and abundance of amorphous material in a mineral sample. Increasing mill scale addition from 2.6 to 10.6 and to 21.2 wt% in an otherwise synthetic Sinter mixture composition designed to form SFCA did not significantly affect the thermal stability ranges of SFCA-I or SFCA, nor did it significantly affect the amount of each of SFCA or SFCA-I, which formed. This was attributed to the low impurity (i.e. Mn, Mg) concentration in the mill scale, and also the transformation to hematite during heating of the wustite and magnetite present in the mill scale, with the hematite available for reaction to form SFCA and SFCA-I.
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Fundamentals of Silico-Ferrite of Calcium and Aluminum (SFCA) and SFCA-I Iron Ore Sinter Bonding Phase Formation: Effects of CaO:SiO_2 Ratio
Metallurgical and Materials Transactions B, 2014Co-Authors: Nathan A. S. Webster, Ian C. Madsen, Anthony J Studer, James R. Manuel, Mark I Pownceby, Justin A. KimptonAbstract:Effects of basicity, B (CaO:SiO_2 ratio) on the thermal range, concentration, and formation mechanisms of silico-ferrite of calcium and aluminum (SFCA) and SFCA-I iron ore Sinter Bonding phases have been investigated using an in situ synchrotron X-ray diffraction-based methodology with subsequent Rietveld refinement-based quantitative phase analysis. SFCA and SFCA-I phases are the key Bonding materials in iron ore Sinter, and improved understanding of the effects of processing parameters such as basicity on their formation and decomposition may assist in improving efficiency of industrial iron ore Sintering operations. Increasing basicity significantly increased the thermal range of SFCA-I, from 1363 K to 1533 K (1090 °C to 1260 °C) for a mixture with B = 2.48, to ~1339 K to 1535 K (1066 °C to 1262 °C) for a mixture with B = 3.96, and to ~1323 K to 1593 K (1050 °C to 1320 °C) at B = 4.94. Increasing basicity also increased the amount of SFCA-I formed, from 18 wt pct for the mixture with B = 2.48 to 25 wt pct for the B = 4.94 mixture. Higher basicity of the starting Sinter mixture will, therefore, increase the amount of SFCA-I, considered to be more desirable of the two phases. Basicity did not appear to significantly influence the formation mechanism of SFCA-I. It did, however, affect the formation mechanism of SFCA, with the decomposition of SFCA-I coinciding with the formation of a significant amount of additional SFCA in the B = 2.48 and 3.96 mixtures but only a minor amount in the highest basicity mixture. In situ neutron diffraction enabled characterization of the behavior of magnetite after melting of SFCA produced a magnetite plus melt phase assemblage.
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in situ diffraction studies of iron ore Sinter Bonding phase formation qpa considerations and pushing the limits of laboratory data collection
Powder Diffraction, 2014Co-Authors: Nathan A. S. Webster, Ian C. Madsen, Anthony J Studer, Mark I Pownceby, Justin A. KimptonAbstract:The formation and decomposition of silico-ferrite of calcium and aluminium (SFCA) and SFCA-I iron ore Sinter Bonding phases have been investigated using in situ synchrotron and laboratory X-ray diffraction (XRD) and neutron diffraction (ND). An external standard approach for determining absolute phase concentrations via Rietveld refinement-based quantitative phase analysis is discussed. The complementarity of in situ XRD and ND in characterising Sinter phase formation and decomposition is also shown, with the volume diffraction afforded by the neutron technique reducing errors in the quantification of magnetite above ~1200 °C. Finally, by collecting 6 s laboratory XRD datasets and using a heating rate of 175 °C min −1 , phase formation and decomposition have been monitored under heating rates more closely approximating those encountered in industrial iron ore Sintering.
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effect of oxygen partial pressure on the formation mechanisms of complex ca rich ferrites
Isij International, 2013Co-Authors: Ian C. Madsen, Nathan A. S. Webster, Mark I Pownceby, Justin A. KimptonAbstract:The formation mechanisms of the complex Ca-rich ferrite iron ore Sinter Bonding phases SFCA and SFCA-I, during heating of a synthetic Sinter mixture in the range 298–1 623 K and at pO2 = 0.21, 5 × 10 –3 and 1 × 10 –4 atm, were determined using in situ X-ray diffraction. SFCA and, in particular, SFCA-I are desirable Bonding phases in iron ore Sinter, and improved understanding of the effect of parameters such as pO2 on their formation may lead to improved ability to maximise their formation in industrial Sintering processes. SFCA-I and SFCA were both observed to form at pO2 = 0.21 and 5 × 10 –3 atm, with the formation of SFCA-I preceding SFCA formation in each case, but via distinctly different mechanisms at each pO2. No SFCA-I was observed at pO2 = 1 × 10 –4 atm; instead, a Ca-rich phase designated CFAlSi, formed at 1 420 K. By 1 456 K, CFAlSi had decomposed to form melt and a small amount of SFCA. Such a low pO2 during heating of industrial Sinter mixtures is, therefore, undesirable, since it would not result in the formation of an abundance of SFCA and SFCA-I Bonding phases. In addition, CFA phase, which was determined by Webster et al. (Metall. Mater. Trans. B, 43(2012), 1344) to be a key precursor phase in the formation of SFCA at pO2 = 5 × 10 –3 atm, was also observed to form at pO2 = 0.21 and 1 × 10 –4 atm, with the amount decreasing with increasing pO2.