scholarly journals Dielectric Performance of a High Purity HTCC Alumina at High Temperatures - A Comparison Study with other Polycrystalline Alumina

2014 ◽  
Vol 2014 (HITEC) ◽  
pp. 000271-000277 ◽  
Author(s):  
Liang-Yu Chen
Keyword(s):  
Dielectric Constant ◽  
High Temperature ◽  
High Temperatures ◽  
High Purity ◽  
Ac Conductivity ◽  
Dissipation Factor ◽  
Alumina Substrate ◽  
Raw Material ◽  
Polycrystalline Alumina ◽  
Dielectric Performance

A very high purity (99.99+%) high temperature co-fired ceramic (HTCC) alumina has recently become commercially available. The raw material of this HTCC alumina is very different from conventional HTCC alumina, and more importantly there is no glass additive in this alumina material for co-firing processing. Previously, selected HTCC and LTCC (low temperature co-fired ceramic) alumina materials were evaluated at high temperatures as dielectric and compared to a regularly sintered 96% polycrystalline alumina (96% Al2O3), where 96% alumina was used as the benchmark. A prototype packaging system based on regular 96% alumina with Au thick-film metallization successfully facilitated long term testing of high temperature silicon carbide (SiC) electronic devices for over 10,000 hours at 500°C. In order to evaluate this new high purity HTCC alumina for possible high temperature packaging applications, the dielectric properties of this HTCC alumina substrate were measured and compared with those of 96% alumina and a previously tested LTCC alumina from room temperature to 550°C at frequencies of 120 Hz, 1 KHz, 10 KHz, 100 KHz, and 1 MHz. A parallel-plate capacitive device with dielectric of the HTCC alumina and precious metal electrodes were used for measurements of the dielectric constant and dielectric loss of the co-fired alumina material in the temperature and frequency ranges. The capacitance and AC parallel conductance of the capacitive device were directly measured by an AC impedance meter, and the dielectric constant and parallel AC conductivity of the dielectric were calculated from the capacitance and conductance measurement results. The temperature and frequency dependent dielectric constant, AC conductivity, and dissipation factor of the HTCC alumina substrate are presented and compared to those of 96% alumina and a selected LTCC alumina. Other technical advantages of this new co-fired material for possible high packaging applications are also discussed.

Electrical Performance of Cofired Alumina Substrates at High Temperatures

2013 ◽  
Vol 10 (3) ◽  
pp. 89-94 ◽  
Author(s):  
Liang-Yu Chen
Keyword(s):  
Dielectric Constant ◽  
High Temperature ◽  
Ac Conductivity ◽  
Large Scale ◽  
Dissipation Factor ◽  
Electrical Performance ◽  
Prototype System ◽  
Polycrystalline Aluminum ◽  
Polycrystalline Alumina ◽  
Dielectric Performance

A 96% polycrystalline alumina (Al2O3) based prototype packaging system with Au thick-film metallization successfully facilitated long term testing of high temperature SiC electronic devices for over 10,000 h at 500°C previously. However, the 96% Al2O3 chip-level packages of this prototype system were not fabricated via a commercial cofire process, which would be more suitable for large scale commercial production. The cofired alumina materials adopted by the packaging industry today usually contain several percent of glass constituents to allow cofiring processes at temperatures usually lower than the regular sintering temperature for alumina. In order to answer the question of whether cofired alumina substrates can provide a reasonable high temperature electrical performance comparable to regular 96% alumina sintered at 1700°C, this paper reports on the dielectric performance of a selected high temperature cofired ceramic (HTCC) alumina substrate and a low temperature cofired ceramic (LTCC) alumina (polycrystalline aluminum oxides with glass constituents) substrate from room temperature to 550°C at frequencies of 120 Hz, 1 KHz, 10 KHz, 100 KHz, and 1 MHz. Parallel-plate capacitive devices with dielectrics of these cofired alumina and precious metal electrodes were used for measurement of the dielectric properties of the cofired alumina materials in the temperature and frequency ranges. The capacitance and AC parallel conductance of these capacitive devices were directly measured by an AC impedance meter, and the dielectric constant and parallel AC conductivity of the dielectric were calculated from the capacitance and conductance measurement results. The temperature and frequency dependent dielectric constant, AC conductivity, and dissipation factor of selected LTCC and HTCC cofired alumina substrates are presented and compared with those of 96% alumina. Metallization schemes for cofired alumina for high temperature applications are discussed to address the packaging needs for low-power 500°C SiC electronics.

Electrical Performance of Co-Fired Alumina Substrates at High Temperatures

2012 ◽  
Vol 2012 (HITEC) ◽  
pp. 000173-000178 ◽  
Author(s):  
Liang-Yu Chen
Keyword(s):  
Dielectric Constant ◽  
High Temperature ◽  
Ac Conductivity ◽  
Large Scale ◽  
Electrical Performance ◽  
Firing Process ◽  
Prototype System ◽  
Polycrystalline Aluminum ◽  
Polycrystalline Alumina ◽  
Dielectric Performance

A 96% polycrystalline alumina (Al2O3) based prototype packaging system with Au thick-film metallization successfully facilitated long term testing of high temperature SiC electronic devices for over 10,000 hours at 500°C previously. However, the 96% Al2O3 chip-level packages of this prototype system were not fabricated via a commercial co-fire process which is more suitable for large scale commercial production. The co-fired alumina materials adopted by the packaging industry today usually contain several percent of glass constituents to provide better adhesion and sealing at interfaces formed during a co-firing process at temperatures usually lower than the regular sintering temperature for alumina. In order to answer the question if co-fired alumina substrates can provide reasonable high temperature electrical performance comparable to those of regular 96% alumina sintered at 1700°C, this paper reports on the dielectric performance of a selected high temperature co-fired ceramic (HTCC) alumina substrate and a low temperature co-fired ceramic (LTCC) alumina (polycrystalline aluminum oxides with glass constituents) substrate from room temperature to 550°C at frequencies of 120 Hz, 1 KHz, 10 KHz, 100 KHz, and 1 MHz. Parallel-plate capacitive devices with dielectrics of these co-fired alumina and precious metal electrodes were used for measurement of the dielectric properties of the co-fired alumina materials in the temperature and frequency ranges. The capacitance and AC parallel conductance of these capacitive devices were directly measured by an AC impedance meter, and the dielectric constant and parallel AC conductivity of the dielectric were calculated from the capacitance and conductance measurement results. The temperature and frequency dependent dielectric constant, AC conductivity, and dissipation factor of selected LTCC and HTCC co-fired alumina substrates are presented and compared to those of 96% alumina. Metallization schemes for co-fired alumina for high temperature applications are discussed to address packaging needs for low power 500°C SiC electronics.

Investigation of the Properties of Alumina-Zirconia Ceramics

2014 ◽  
Vol 1040 ◽  
pp. 245-249
Author(s):  
Aleksander S. Ivashutenko ◽  
Alexandr V. Kabyshev ◽  
Nikita Martyushev ◽  
Igor G. Vidayev
Keyword(s):  
Dielectric Constant ◽  
Electric Conductivity ◽  
High Temperatures ◽  
Electrostatic Field ◽  
Mechanical Characteristics ◽  
Ferroelectric Properties ◽  
Dissipation Factor ◽  
Zirconia Ceramics ◽  
Measurement Results ◽  
Dielectric Dissipation Factor

The article focuses on the investigation of the properties of alumina-zirconia ceramics possessing high mechanical characteristics and good conductivity at high temperatures. Measurement results of the dielectric dissipation factor, dielectric constant, electric conductivity when using direct and alternating current for the ceramics samples of 80%(ZrO2-3%Y2O3)-20% Al2O3 composition are presented in the paper. Measurements were conducted simultaneously in the electrostatic field in vacuum while heating the samples to the temperatures ranging from 300 to 1700K. Investigations showed that alumina-zirconia ceramics at high temperatures obtains ferroelectric properties not typical of these structures.

Improvement of Dielectric Performance of a Prototype AlN High Temperature Chip-level Package

2011 ◽  
Vol 2011 (HITEN) ◽  
pp. 000052-000057 ◽  
Author(s):  
Liang-Yu Chen
Keyword(s):  
High Temperature ◽  
Dielectric Properties ◽  
High Temperatures ◽  
Substrate Surface ◽  
Substrate Material ◽  
Glass Coating ◽  
Temperature Dependent ◽  
High Temperature Electronics ◽  
Dielectric Performance ◽  
Parasitic Parameters

Aluminum nitride (AlN) has been proposed as a packaging substrate material for reliable high temperature electronics operating in a wide temperature range. However, it was discovered in a recent study that the dielectric properties of some commercial polycrystalline AlN materials change quite significantly with temperature at high temperatures. These material properties resulted in undesired large and temperature-dependent parasitic parameters for a prototype chip-level package based on an AlN substrate with the yttrium oxide dopant. This paper reports a method using a coating layer of a commercial thick-film glass on the AlN substrate surface to significantly reduce both the parasitic capacitances and parasitic conductances between neighboring inputs/outputs (I/Os) of a prototype AlN chip-level package. The parasitic parameters of 8-I/Os low power chip-level packages with the insulating glass coating were characterized at frequencies from 120 Hz to 1 MHz between room temperature and 500°C. These results were compared with the parameters of AlN packages without the glass coating. The results indicate that the parasitic capacitances and conductances between I/Os of the improved prototype AlN packages are significantly reduced and stable at high temperatures. The method using a glass coating provides a feasible way to mitigate the temperature dependence of dielectric properties of AlN and further utilize AlN as a reliable packaging substrate material for high temperature applications.

The self-propagation high-temperature synthesis of ultrafine high purity tungsten powder from scheelite

1996 ◽  
Vol 11 (7) ◽  
pp. 1825-1830 ◽  
Author(s):  
J. C. Jung ◽  
S. G. Ko ◽  
C. W. Won ◽  
S. S. Cho ◽  
B. S. Chun
Keyword(s):  
High Temperature ◽  
High Temperatures ◽  
High Purity ◽  
Tungsten Powder ◽  
The Self ◽  
Molar Ratio ◽  
Temperature Synthesis ◽  
Complete Reduction ◽  
High Temperature Synthesis ◽  
Hcl Solution

High-purity tungsten was prepared by the self-propagating high-temperature synthesis (SHS) process from a mixture of CaO · WO3 and Mg. The complete reduction of CaO · WO3 required a 33% excess of magnesium over the stoichiometric molar ratio Mg/CaO · WO3 of 3: 1. The MgO and CaO in the product were leached with an HCl solution. The product tungsten had a purity of 99.980% which was higher than that of the reactants. The high purity results because the nontungsten reactants and products are volatilized by the high temperatures generated during the rapid exothermic SHS reaction and are dissolved during HCl leaching of the product.

High Temperature Corrosion Product Films on Aluminum

CORROSION ◽  
1959 ◽  
Vol 15 (1) ◽  
pp. 23-24 ◽  
Author(s):  
V. H. TROUTNER
Keyword(s):  
Electron Microscope ◽  
High Temperature ◽  
Corrosion Product ◽  
Corrosion Inhibition ◽  
High Temperatures ◽  
Electron Micrographs ◽  
High Purity ◽  
High Temperature Corrosion ◽  
Aqueous Environments ◽  
Metal Electron

Abstract The corrosion product films formed on aluminum in aqueous environments at high temperatures have been examined with the electron microscope. A technique is described for the preparation of electron microscope replicas of the surface of the corrosion product films adjacent to the metal. Electron micrographs are shown of corrosion product films formed during various stages of corrosion in high purity water, and in corrosion inhibited systems. Corrosion inhibition was found to be assocated with different crystalline structures of the corrosion product films. 2.3.6

Magnesium reduction of WO3 in a self-propagating high-temperature synthesis (SHS) process

1995 ◽  
Vol 10 (4) ◽  
pp. 795-797 ◽  
Author(s):  
Seog Gueon Ko ◽  
Chang Whan Won ◽  
Byong Sun Chun ◽  
H.Y. Sohn
Keyword(s):  
High Temperature ◽  
High Temperatures ◽  
High Purity ◽  
Exothermic Reaction ◽  
The Self ◽  
Molar Ratio ◽  
Temperature Synthesis ◽  
Complete Reduction ◽  
High Temperature Synthesis ◽  
Hcl Solution

High-purity tungsten was prepared by the self-propagating high-temperature synthesis (SHS) process from a mixture of WO3 and Mg. The MgO in the product was leached with an HCl solution. The complete reduction of WO3 required a 33% excess of magnesium over the stoichiometric molar ratio Mg/WO3 of 3. The product tungsten had a purity of 99.980% which was higher than that of the reactant WO3. This is because the impurities were either volatilized at the high temperatures generated during the rapid exothermic reaction or dissolved into the HCl solution during leaching.

THE THERMAL CONDUCTIVITY OF PLATINUM BETWEEN 300 AND 1 000 °K

1966 ◽  
Vol 44 (12) ◽  
pp. 3173-3183 ◽  
Author(s):  
M. J. Laubitz ◽  
M. P. van der Meer
Keyword(s):  
Thermal Conductivity ◽  
Electrical Resistivity ◽  
High Temperature ◽  
High Temperatures ◽  
Fermi Energy ◽  
High Purity ◽  
Lorenz Number ◽  
Increasing Function

The thermal conductivity of high-purity platinum was measured between 300 and 1 000 °K. The results obtained agree very well with the previously reported work of Bode and of Martin and Sidles, but at higher temperatures are in definite disagreement with the results of Powell and Tye. The observed variation of the thermal conductivity with temperature implies that at high temperatures the (electronic) Lorenz number of platinum is an increasing function of temperature, exceeding in magnitude the Sommerfeld value. Such behavior of the Lorenz number can be understood qualitatively if one assumes a low Fermi energy for platinum, an assumption usually made to account for the behavior of its high-temperature electrical resistivity.

Dielectric Properties and Thermal Conductivity of Poly(vinylidene fluoride)-Based Composites with Graphite Nanosheet and Nickel Particle

2019 ◽  
Vol 19 (6) ◽  
pp. 3591-3596 ◽  
Author(s):  
Lirong Wu ◽  
Dandan Yang
Keyword(s):  
Thermal Conductivity ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Ac Conductivity ◽  
Vinylidene Fluoride ◽  
Filler Loading ◽  
Graphite Nanosheet ◽  
Dielectric Performance ◽  
Poly Vinylidene Fluoride

The nickel (Ni) particles and graphite nanosheet (GNS) filled poly(vinylidene fluoride) (PVDF) composites were prepared by solution blending and hot-press processing in the magnetic field. The influence of Ni particles and GNS fillers for the structure, morphology, AC conductivity, dielectric properties and thermal conductivity of composites was investigated. The results showed that the β-phase crystals of PVDF matrix was increased obviously. The AC conductivity, dielectric constant and dielectric loss of PVDF/Ni/GNS composite reached to 10−9 s/cm, 62 and 0.39 when the filler loading was 11 wt.% at 102 Hz, respectively. At the ratio of 15 wt.% filler, the AC conductivity of PVDF/Ni/GNS composite was vastly improved to 10−6 s/cm, however, the dielectric constant increased to ~80 and dielectric loss was over 600 at 102 Hz. By comparing the dielectric performance of PVDF/Ni/GNS, PVDF/Ni and PVDF/GNS composites, it is found that the parallel arrangement of the filler conduces to improve the dielectric properties of the composites. Furthermore, the thermal conductivity of PVDF/Ni/GNS composites increased with the increase of Ni and GNS contents and the value raised to over 0.5 W/mK when filler loading was 15 wt.%.

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