Glass Coefficient Of Thermal Expansion Research Articles

Analysis of the thermal expansion coefficient of glass- and carbon-fibre-reinforced composites

With the development of manufacturing processes, an increase in the importance of metal-fibre composites in materials engineering is observed. These are materials consisting of appropriately arranged layers of metal and various types of fibres. The very wide use of composite materials in the construction of machine and equipment components means they are often exposed to work in variable temperature conditions. The aim of this article was analysis of the thermal expansion of typical composites: carbon fibre-reinforced polymer, glass fibre-reinforced polymer, glass-reinforced aluminium laminate and carbon-fibre reinforced aluminium laminate. EN AW-6060 aluminium alloy was used as the reference material. The aim of the dilatometric tests was to determine the coefficient of thermal expansion and the dimensional stability of composite materials at elevated temperatures up to 100 °C. The EN AW-6060 aluminium alloy was characterized by the highest linear expansion coefficient (20.27×10−6 1/K). Composites containing glass fibres were characterized by the lowest positive linear thermal expansion coefficient. Among the composite materials tested, CARALLs exhibit the lowest thermal expansion coefficient.

Performance studies of novel all-glass heat pipe evacuated collector tube integrating numerical simulation and experiment method

Metal heat pipe evacuated collector tube (ECT) suffer from cracks in the joint between the glass outer layer and the metal heat pipe due to the large difference in thermal expansion coefficients of glass and metal, resulting in non-industrialization. In this paper, the metal heat pipe is replaced with a glass heat pipe to form an all-glass heat pipe ECT to address the air-tight sealing problem, and a reflective film was added to the lower part of the outer tube to improve energy. According to these results, the thermal stress of 0.279 MPa is well below the bearing range of 40–120 MPa, and the maximum thermal strain of 0.175 mm/mm is also far less than the affordable value of 120 mm/mm, inducting the all-glass structure fully copes with the transient local heating changes. The optical efficiency is increased by 0.17 % by the addition of the reflective film, and yielding an energy output of 87 W and a maximum volume fraction of 4.8 % for liquid–water in the quasi-thermal equilibrium state. At the same time, the evaporation operating speed of the vapor can be increased by improving the solar radiation flux density and reducing thermal losses, and optimizing the multi-level and cross-scale vapor vortices can also improve the convective heat transfer rate, so they are future directions for development. However, there are the limitations of decreasing the thermal conductivity and increases the resistance due to the heat pipe conversion from metal to glass.

Thermal expansion and the glass transition

Melting is well understood in terms of the Lindemann criterion, which essentially states that crystalline materials melt when the thermal vibrations of their atoms become so vigorous that they shake themselves free of the binding forces. This picture does not necessarily have to hold for glasses, where the nature of the solid–liquid cross-over is highly debated. The Lindemann criterion implies that the thermal expansion coefficients of crystals are inversely proportional to their melting temperatures. Here we find that, in contrast, the thermal expansion coefficient of glasses decreases more strongly with increasing glass temperature, which marks the liquid–solid cross-over in this material class. However, this proportionality returns when the thermal expansion coefficient is scaled by the fragility, a measure of particle cooperativity. Therefore, for a glass to become liquid, it is not sufficient to simply overcome the interparticle binding energies. Instead, more energy must be invested to break up the typical cooperative particle network that is common to glassy materials. The thermal expansion coefficient of the liquid phase reveals similar anomalous behaviour and is universally enhanced by a constant factor of approximately 3. These universalities allow the estimation of glass temperatures from thermal expansion and vice versa.

Properties and mechanism of amorphous lead aluminosilicate passivation layers used in semiconductor devices through molecular dynamic simulation

With the rapid development of the semiconductor industry, the glass passivation process is being optimized as an important process for the protection of electronic components. Lead aluminosilicate glasses, with a stable network structure, adjustable thermal expansion coefficient and high voltage resistance, are valuable for use in power devices such as diodes. In this work, the effects of PbO content on the expansion and thermal properties of lead aluminosilicate glasses were investigated by combining molecular dynamics simulations and experimental tests. The relationship between structural changes and performance is analyzed in detail, and the passivation mechanism of lead aluminosilicate glass for semiconductor devices is also elucidated. The results show that the thermal expansion coefficients of glass and silica wafers can match the glass composition with PbO contents of 15–25 mol%. The diffusion ability of Pb atoms in the network structure is also the lowest in this concentration range. The glass transition temperature (Tg) and fluidity at high temperature, both decrease with increasing PbO content. In addition, the glass powder was applied to MOS devices for electrical performance testing. It was found that when the PbO content was at 20 mol%, the glass passivation layer and the silicon wafer had tight interfacial contact after sintering. The interfacial defect density reached the minimum value (5.276 × 1010 cm−2eV−1) along with a high fixed charge density (2.124 × 1010 cm−2). In other words, the glass powder composed of 20PbO-4.8Al2O3-75.2SiO2 (mol%) can minimize the interfacial carrier compound, reduce the interfacial contact resistance and increase the current density to achieve a more desirable interfacial passivation effect in semiconductor devices.

The Relationship between the Structure and Thermal Properties of Bi2O3-ZnO-B2O3 Glass System

The influence of Bi2O3 and melting temperature on the thermal and structural properties of xBi2O3-(60-x) ZnO-40B2O3 glasses has been investigated in this study. It is expected that these factors can be used to control the degree of reduction of Bi2O3, and the relationship between these factors and the color change of the process for bismuth glass is discussed. Due to high-temperature melting, the bismuth-doped borate glasses have changed into dark/black from original transparent yellow and the light transmittance will decrease, so it is not used in optical applications. The thermal properties of glass are measured by a thermomechanical analyzer (TMA), and the glass structure is analyzed by FTIR and XPS. The results show that the glass is mainly composed of [BiO6] octahedron, [BiO3] triangle, [BO4] tetrahedron, and triangle [BO3] units, and the network of the glass system is mainly bonded by B-O-B, B-O-Zn, B-O-Bi, and Bi-O-Bi. The glass thermal expansion coefficient (CTE) of this glass system increases with the increase of Bi2O3 content, and the O1s nuclear electron binding energy shifts to the lower energy direction with the increase of Bi2O3 addition. In terms of FTIR, as the melting temperature rises, the B-O-B bonding vibration concentration of [BO4] inside the borate glass decreases, and the density of B-O-B bonding vibration of [BO3] increases, Moreover, the increase in melting temperature increases the probability of reducing Bi ions to Bi0, reduces the bonding of Bi-O-B, and increases the bonding of B-O-B, and the CTE also slightly decreases.

Study of high-alumina-silicon glass structure and performance modified by Li2O replacing Na2O

The effect of various alkali metal content (Li, Na) in high-alumina-silicon cover glass on the structure and performance of the glass is investigated in this work. The findings of the performance investigation show that the density, chemical stability, and thermal expansion coefficient of glasses display nonlinear changes. In addition, the typical thermal and dielectric properties are unaffected by combined alkali. The integrity of the glass network structure and the tightness of ions alternately vary due to the influence of lithium ion's own features, which is origin of MAE according to the results of XPS and infrared spectroscopy. It is certain that altering the Li/Na ratio can optimize this type of glass, and the defined range has guiding relevance for the design and production of cover glass.

FE Simulation Model for Warpage Evaluation of Glass Interposer Substrate Packages

Glass interposer substrates have attracted growing interest as an alternative to traditional organic and silicon-based interposers for 3-D integrated circuit (IC) and 2.5-D through silicon via (TSV) packages in recent years. However, while glass substrates have the advantages of excellent electrical isolation, superior RF performance, good coefficient of thermal expansion (CTE) adjustability, and the potential for large-scale fabrication, they are inherently brittle. Consequently, an appropriate choice of glass and epoxy molding compound (EMC) material is essential for minimizing the warpage of the molded wafer. To facilitate the package design process, this study, therefore, develops an ANSYS simulation model to predict the warpage of the molded glass wafer given the use of different glass and EMC materials. The validity of the simulation model is confirmed by comparing the numerical results for the warpage of an 8-in molded glass wafer with the experimental measurements obtained using an Advanced Metrology Analysis (aMA) system. Single-factor-analysis experiments are then conducted to examine the effects of five different control factors, namely, the glass substrate thickness, the glass CTE, the glass modulus, the EMC CTE, and the EMC modulus, on the warpage performance of the molded glass wafer. The simulation results provide useful guidelines for the design of robust glass substrate packages.

Effect of glass-removal on the magnetostriction and magnetic switching properties in amorphous FeSiB microwires

Abstract Results on the influence of glass-removal on the magnetostriction, magnetic switching properties and domain wall propagation in amorphous Fe77.5Si17.5B15 microwires are reported. Glass removal releases high thermoelastic stresses originated by the difference in thermal expansion coefficients of glass and metal, which reduces the coercivity, increases the domain wall mobility and decreases the local nucleation fields and their distributions. Evening the distribution of nucleation fields and eliminating the local surface defects due to glass removal increase the field range of single domain wall propagation regime. It was also found that the saturation magnetostriction coefficient significantly decreases after glass removal, which strengthens the impact of the reduced magnetoelastic anisotropy. The effect of glass removal on magnetostriction was previously observed only in Co-rich microwires with small negative magnetostriction. Understanding the factors that control the magnetic switching and domain wall dynamics is of interest for practical applications in sensing, storage and logic devices.

Study on non-isothermal crystallization kinetics of the BaO-CaO-Al2O3-B2O3-SiO2 glass for IT-SOFCs sealing

The crystallization ability plays a key role in effecting thermal ability of sealing glass for intermediate temperature-solid oxide fuel cells (IT-SOFCs) to prevent fuel leakage during operation and insulate the cell stack from the external atmosphere. Herein, using differential thermal analysis (DTA) techniques, the growth mode of crystals precipitated in BaO-CaO-Al2O3-B2O3-SiO2 (BCABS) sealing glass through the heat treatment was calculated in terms of non-isothermal crystallization kinetics for the first time. The calculated results showed that the average kinetic exponent n of the glass was approximatively 1, indicating that the crystal nucleuses became to form and further grew with one-dimensional mode from the surface inwards. Scanning electron microscope (SEM) observations clearly revealed that a large number of one-dimensional filamentous crystals have been formed on the interface between the sealing glass and the electrolyte after the heat treatment at 973 K for 100 h, which perfectly coincided with the theoretical calculations, and the glass was well combined with the electrolyte without any visible cracks or peeling at the interface. The one-dimensional growth of hexagonal BaAl2Si2O8 crystals verified by X-ray diffraction (XRD) could effectively decelerate the decrease of thermal expansion coefficient of glass to ensure enhance the thermo-stability of the BCABS sealing glass for IT-SOFC.

Board-Level Thermal Cycling and Drop-Test Reliability of Large, Ultrathin Glass BGA Packages for Smart Mobile Applications

Glass substrates are emerging as a key alternative to silicon and conventional organic substrates for high-density and high-performance systems due to their outstanding dimensional stability, enabling sub-5- $\mu \text{m}$ lithographic design rules, excellent electrical performance, and unique mechanical properties, key in achieving board-level reliability at body sizes larger than $15\times15$ mm2. This paper describes the first demonstration of the board-level reliability of such large, ultrathin glass ball grid array (BGA) packages directly mounted onto a system board, considering both their thermal cycling and drop-test performances. To investigate board-level reliability, glass BGA packages, $18.5\times18.5$ mm2 in body size and 100 $\mu \text{m}$ in thickness, were first designed and fabricated with a daisy-chain pattern. The glass test vehicles were fabricated at panel level, and then BGA balled by ball drop process with SAC105 solder balls, 250 $\mu \text{m}$ in diameter at 400- $\mu \text{m}$ pitch. After singulation, the glass packages were mounted onto printed circuit boards using standard surface mount technology assembly processes, and then subjected to reliability testing through thermal cycling and drop tests following JEDEC reliability standards. The effect of the coefficient of thermal expansion (CTE) of glass was evaluated by investigating low- and high-CTE glass substrates, with the CTEs of 3.8 and 9.8 ppm/°C, respectively. While all glass packages passed 1000 thermal cycles at −40/125 °C as predicted by thermomechanical modeling using the Engelmaier–Wild model, the fatigue life of high-CTE samples exceeded 5000 thermal cycles. In addition, 28/30 drop-test samples passed the required 40 and 200 drops on corner and inner circuits, respectively, with no clear effect of the glass CTE. The predominant failure modes were systematically identified for both reliability tests.

Novel glass substrates for minimizing thermal stress development during electronic device packaging process

Abstract Glass can be utilized for support or career substrate in large size packaging process since it has excellent mechanical and optical properties. However, the thermal stress caused by a mismatch of coefficient of thermal expansion (CTE) causes an unneglectable warpage during a thermal process. In order to overcome this thermal stress issue, we have developed novel glasses that have finely tuned CTE characteristics to fit each packaging process. In this paper, we will report on a glass substrate whose CTE is perfectly matched with that of Si, and a series of glass substrates whose CTEs are controlled in sub-ppm order and within the range of 3.3 ~ 12.0 ppm/°C. To evaluate the effect of glass CTE on the thermal stress management, the warpage behavior of Si wafer after glass wafer bonding were investigated by both numerical simulation and experiment. Both results indicate that a small CTE mismatch can cause an unneglectable wafer warpage during the thermal process. Thus sub-ppm order control of glass CTE is essential for minimizing thermal stress development in large size packaging process. The glass substrate with Si matched CTE is suitable for the process where glass and Si are contact directly, e.g. Si back grinding process or through glass via (TGV) technology. The series of glass substrates whose CTEs are finely controlled in a high range are useful when the packaging process utilizes high amount of resins, such as Fan-Out wafer level packaging process.

Calculation of thermal expansion coefficient of glasses based on topological constraint theory

In this work, the thermal expansion behavior and the structure configuration evolution of glasses were studied. Degree of freedom based on the topological constraint theory is correlated with configuration evolution; considering the chemical composition and the configuration change, the analytical equation for calculating the thermal expansion coefficient of glasses from degree of freedom was derived. The thermal expansion of typical silicate and chalcogenide glasses was examined by calculating their thermal expansion coefficients (TEC) using the approach stated above. The results showed that this approach was energetically favorable for glass materials and revealed the corresponding underlying essence from viewpoint of configuration entropy. This work establishes a configuration-based methodology to calculate the thermal expansion coefficient of glasses that, lack periodic order.

Temperature dependence of the off‐diagonal magnetoimpedance in sensor configuration utilizing Co‐rich amorphous wires

For sensor operation, the temperature stability is of primary importance. In this work, we have investigated the temperature dependence of the magnetoimpedance (MI) in glass‐coated Co‐based amorphous wires which are widely used as MI sensing elements. The magnetic alloy has high Curie and crystallization temperatures, yet, the MI change at moderate temperatures of 20–90 °C and low‐magnetic fields can be about 100%. This is explained by high‐temperature sensitivity of the residual stress due to fast solidification and the difference in thermal expansion coefficients of glass and metal. To reduce the temperature effect, annealing treatment was proposed and applied to the whole sensing element in off‐diagonal configuration comprising the MI wire and detection coil. Annealing treatment at a temperature of 160 °C during 2–3 min makes it possible to significantly improve both the magnetic field sensitivity and temperature stability. After annealing, the output voltage sensitivity in the linear region ( increases more than 2.5 times and shows little variations with temperature up to 90 °C. For higher magnetic fields, the MI profile still shows noticeable change with temperature: the maximum of the output voltage decreases at a rate of about 0.15%/°C as the temperature is increased. After optimum annealing, the MI curves become almost symmetrical suggesting that a well‐defined circumferential anisotropy is established.

Innovated Process Integration for Panel Size Glass Substrate Manufacturing for SiP Application

Although Silicon interposer has good performance, however high cost is still the major issue and limits its high volume adoption. Therefore to decrease the assembly cost or develop low cost, high density interconnect interposer technology is the keys to enable 2.5D SiP integration. One possibility is to develop low cost interposer by adopting the alternative materials instead of Silicon. The glass, low CTE polymer material, ceramic, etc. may be included. Glass represents an attractive choice with potential of tailorable properties dependent on specific glass composition. By targeting the coefficient of thermal expansion (CTE), the CTE of glass can be made to match perfectly with silicon dies and for reliable package. In addition, the advantages of using glass for interposer derive from process flexibility for size and thickness since the glass fusion process provides sheets with dimensions of more than three meters. It is straight forward to provide glass substrate of almost any size needed. Large glass panels are ideally suited for fabrication of interposer where the panel process is expected to provide large number of interposers in each run compared with wafer processing. Additionally, the two sided processing of the panel, the avoidance of Si wafer CMP processes further enable lower unit cost for the interposer Consequently, glass is an ideal interposer material due to its insulating property, large panel size availability, high modulus and ability to tailor CTE. In this paper, we successfully demonstrate manufacturing feasibility of glass substrate with 4 build-up layers starting with a thin glass panel in 508mm×508mm panel size format and under the IC substrate manufacturing environment. Glass thickness of 100~300um could be processed through the IC substrate HVM line. The laser via in via or direct metallization technology could be selected for double side electrical connection. The copper line width/space of 8/8um was demonstrated by current substrate HVM line. By adopting advanced lithography process and material, line width/space less than 2/2um was achievable. TCT Reliability test without glass crack results will also be discussed.

Application of Thermophysical Methods for Oxide/Silicate Glasses

An brief overview of the selected thermo-physical measurements realized in the VILA laboratories for the glass industry and for the fundamental research of glass is presented. Among the routine measurements realized for the glass industry the thermodilatometry for measuring the glass transition temperature, and linear thermal expansion coefficients of glass and metastable glassforming melt are described in detail. The fact that the glass transition temperature is not a single valued physical quantity is stressed in connection with the measurement time temperature schedule. The probably most important quantity related to the glass production technology is the viscosity. Its measurement in the range extending ten orders of magnitude is described. The combination of the falling ball method, the rotation viscosimetry and the thermomechanical analysis is needed to cover the above viscosity range. Among the methods used in the fundamental research of glass structure and properties the study of structural relaxation is overviewed. Here the own method of combined viscous flow and structure relaxation TMA measurement is described in detail.

Measurement Principle of Glass Thermal Expansion Coefficient and Technology Application of DIL402PC Dilatometer

The paper introduces the measuring principle of glass thermal expansion coefficient. It expresses the features and advantages of the linear variable differential transformer measuring principle by comparing the thermal expansion coefficient measurement methods analysis. Meanwhile, the paper introduces DIL402PC dilatometer measuring devices and measurement procedures. It use standard samples to execute thermal expansion instrument system check from the accuracy and repeatability. The result shows thermal expansion coefficient of linear expansion instrument bias of DIL402PC dilatometer is within the error range of the theoretical value. The process proves it has a wide range of applications.

Performance of Cu(In,Ga)Se2 solar cells using nominally alkali free glass substrates with varying coefficient of thermal expansion

In this report, Cu(In,Ga)Se2, CIGS, solar cell devices have been fabricated on nominally alkali free glasses with varying coefficients of thermal expansion (CTE) from 50 to 95 * 10−7/ °C. A layer of NaF deposited on top of the Mo was used to provide Na to the CIGS film. Increasing the glass CTE leads to a change of stress state of the solar cell stack as evidenced by measured changes of stress state of the Mo layer after CIGS deposition. The open circuit voltage, the short circuit current density, and the fill factors, for solar cells made on the various substrates, are all found to increase with CTE to a certain point. The median energy conversion efficiency values for 32 solar cells increases from 14.6% to the lowest CTE glass to 16.5% and 16.6%, respectively, for the two highest CTE glasses, which have CTE values closest to that of the soda lime glass. This is only slightly lower than the 17.0% median of soda lime glass reference devices. We propose a model where an increased defect density in the CIGS layer caused by thermal mismatch during cool-down is responsible for the lower efficiency for the low CTE glass substrates.

Study on Dependability and Repeatability of Measurement Method of Mean Linear Thermal Expansion Coefficients of Glasses

Coefficient of mean linear thermal expansion is an important physical property of glasses. It is the key thermodynamic property to evaluate the thermal stability and matching sealing of glasses. The measurement results of coefficient of mean linear thermal expansion obtained by different dilatometers showed that glass expands slowly with nonlinearity below 50 °C. It suggested that the initial temperature of measurement would be set above 50 °C, as behaves better repeatability and reliability of measurement than 20 °C as standard method set.

Microstructural analysis of glass-steel interface

Glass of 60SiO2–15CaO–10Al2O3–10Na2O–5TiO2 composition was synthesized. Crystallization behavior was monitored by differential thermal analysis and thermal gravimetric analysis. Structural analysis was done by X-ray diffraction and scanning electron microscope. A protective coating of this glass was developed on duplex steel substrate. The interfacial characteristic of glass-duplex steel was analyzed under scanning electron microscope. To monitor the stability of coating even at high temperature, the thermal expansion coefficient of glass and steel was observed separately. This study demonstrates that the glass used in present investigation can protect the surface of steel even under adverse environmental conditions.

Low-Cost Thin Glass Interposers as a Superior Alternative to Silicon and Organic Interposers for Packaging of 3-D ICs

Interconnecting integrated circuits (ICs) and 3-D-ICs to the system board (printed circuit board) are currently achieved using organic or silicon-based interposers. Organic interposers face several challenges in packaging 2-D and 3-D-ICs beyond the 32-nm node, primarily due to their poor dimensional stability and coefficient of thermal expansion (CTE) mismatch to silicon. Silicon interposers made with back-end of line wafer processes can achieve the required wiring and I/O density, but their high-cost limit them to high-performance applications. Glass is proposed as a superior alternative to organic and silicon-based interposers for packaging of future ICs and 3-D-ICs with highest I/Os at lowest cost. This paper presents for the first time a novel thin and large panel glass interposer capable of scaling to 700 mm and larger panels with potential for significant cost reduction over interposers made on 200-mm or 300-mm wafers. The formation of small through vias at high speed has been the biggest technical barrier for the adoption of glass as an interposer and system substrate; and this paper describes pioneering research in via-formation in thin glass substrates, using a novel “polymer-on-glass” approach. Electrical modeling and design of through package vias (TPVs) in glass is discussed in detail, and the feasibility of 50-μm pitch TPVs in 180-μm thin glass substrates has been demonstrated. The excellent surface finish and low CTE of glass leads to increased I/O density, and increased functionality per unit area leading to system miniaturization.