News | | Page 3 INLABS

Category Archives: News

Inventory the Ceramic Components in Plasma Etching Equipment

Plasma etching technology is an indispensable processing technology in the preparation of ultra large scale integrated circuits. As the size of semiconductor transistors sharply decreases and the energy of halogen like plasma increases, the problem of wafer contamination becomes increasingly prominent. The requirements for the material”s resistance to plasma corrosion in the cavity of plasma etching equipment under high-density plasma conditions during wafer processing are becoming increasingly stringent. The new generation of etching technology requires stronger and more reliable materials to solve problems such as plasma corrosion, particle generation, metal pollution, and oxygen decomposition.

Ceramics are Key Materials for Plasma Etching Equipment Components

Compared to organic and metal materials, ceramic materials generally have good physical and chemical corrosion resistance, as well as high operating temperatures. Therefore, in the semiconductor industry, ceramic materials have become the core component manufacturing material for semiconductor wafer processing equipment. The components of ceramic materials used in plasma etching equipment mainly include window mirrors, focusing rings, electrostatic chucks, nozzles, cavities, gas dispersion discs, etc.

The main characteristics of plasma etched ceramic materials inside the etching machine cavity are:

1. High purity and low metal impurity content;
2. The chemical properties of the main components are stable, especially the chemical reaction rate with halogen corrosive gases is low;
3. High density with few open pores;
4. Fine grain size and low content of grain boundary phases;
5. Has excellent mechanical properties and is easy to produce and process;
6. Some components may have other performance requirements, such as good dielectric performance, conductivity, or thermal conductivity. In a plasma environment, the selection of ceramic materials depends on the working environment of the core components and the quality requirements for the process products, such as plasma etching resistance, electrical performance, insulation, etc.

Application of Ceramics in Core Components of Plasma Etching Equipment

1. Cavity

The material of the etching machine chamber is the main source of wafer contamination, and the degree of influence of plasma etching on it determines the yield, quality, and stability of the etching process of the wafer. High purity alumina ceramics are a good plasma corrosion resistant material, which can provide reliable plasma impedance as a chamber material. However, the alumina ceramic cavity in the plasma etching machine equipment belongs to large-sized ceramics. The production of such large-sized and ultra-high purity alumina ceramics has problems such as easy deformation, cracking, and difficulty in sintering and densification. To obtain high-density and high-purity alumina ceramics, high requirements are placed on the purity of the powder and the preparation process.

2. Focusing Ring

The focusing ring aims to improve the etching uniformity around the edges or periphery of the wafer, fix the wafer in place to maintain plasma density and prevent contamination of the wafer sides. When used with electrostatic suction cups, the wafer is placed on the focusing ring and secured in place by electrostatic charges. Due to the direct contact between the focusing ring and the plasma in the vacuum reaction chamber, it is necessary to use materials that are resistant to plasma corrosion and have conductivity similar to that of silicon wafers. The materials of the focusing ring include conductive silicon and silicon carbide.

Conductive silicon, as a commonly used focusing ring material, has a conductivity almost similar to that of silicon wafers. However, its disadvantage is poor corrosion resistance in fluorinated plasma. After a period of use, the material of etching machine components often exhibits severe corrosion, seriously reducing its production efficiency. Silicon carbide has similar electrical conductivity and good ion resistance to silicon. The sub etching performance is suitable for focusing ring materials. Usually, the focusing ring is formed by depositing the silicon carbide generated by chemical reactions into a certain shape through vapor deposition, and then mechanically processing the silicon carbide into a focusing ring according to specific usage conditions.

3. Electrostatic chuck (ESC)

During the entire etching process of the chip, it is adsorbed and fixed by the electrostatic chuck (ESC) in the lower electrode system, and RF is introduced to the electrostatic chuck, which forms a DC bias (DC bias) on the chip.This facilitates the etching reaction of plasma on the chip. At the same time, the electrostatic chuck will achieve temperature control on the chip to promote the uniformity of chip etching. The interior of the electrostatic chuck mainly consists of a dielectric layer, a base, and a heating layer. Aluminum oxide and aluminum nitride are commonly used as dielectric layer materials in the production of electrostatic chucks due to their high thermal conductivity and low coefficient of thermal expansion.

4. Nozzles

The nozzle is used for precise gas flow rate and uniform control to evenly disperse gas into the etching process chamber. These components require high plasma resistance, dielectric strength, and strong corrosion resistance to process gases and by-products. The commonly used ceramic materials include aluminum nitride ceramics and aluminum oxide ceramics. At present, ceramic 3D printing technology can also be used to produce ceramic nozzles in the etching chamber, improving product manufacturing efficiency and usage stability.

Silicon Nitride Ceramics: Hard Core Basic Materials In The New Energy Era

1. Tesla leads the wind vane for silicon nitride ceramic substrates

With Tesla taking the lead in using a large number of silicon nitride ceramic substrates in Model 3 SIC MOSFET devices to solve module heat dissipation problems, silicon nitride ceramic materials have once again entered the industry”s sight. Recently, with the vigorous promotion of 800V high-voltage fast charging technology in new energy vehicles, the issue of corrosion of steel ball bearings in traditional drive motors has received attention. Tesla has adopted Japanese NSK hybrid ceramic bearings in the motor output shaft, with bearing balls composed of 50 silicon nitride bearing balls.

2. Mainstream application products of silicon nitride

The rapid growth in downstream demand for new energy, energy storage, and new energy vehicles will further drive the rapid growth of the domestic market for mainstream application products such as silicon nitride structural components (such as silicon nitride ceramic balls, silicon nitride valve balls, and silicon nitride grading wheels) and silicon nitride ceramic substrates.

1). Silicon nitride ceramics as the application trend of future bearings

At present, traditional steel bearings are still the main type, and silicon nitride ceramic bearings, as a new type of application material in the future, have broad potential for substitution. Rolling bearings are composed of rings, rolling elements, retainers, lubricating grease, and sealing elements. Silicon nitride all ceramic ball bearings refer to rolling elements and rings made of silicon nitride material. Under the wave of electrification, steel ball bearings are currently facing problems such as inability to break through the limitations of higher speed requirements, inability to meet the low noise requirements of users for whole vehicles, and corrosion under higher voltage and high switching frequency requirements. Compared with traditional steel balls and other ceramic materials, silicon nitride ceramics have the characteristics of lightweight, high hardness and heat resistance, low friction, corrosion resistance, self-lubricating, etc., and are considered the best material for manufacturing ceramic bearings in the future.

2). Silicon nitride ceramic substrate is the ceramic substrate material with the best comprehensive performance

With the increasing power density of IGBT and third-generation semiconductor power devices, mainstream aluminum oxide substrates with low thermal conductivity, low mechanical strength, poor toughness, high dielectric constant, and high thermal expansion rate can no longer meet the needs of the new energy vehicle market. Silicon nitride ceramics are considered to have the best comprehensive performance as ceramic substrate materials due to their excellent mechanical strength, good chemical stability, and thermal shock resistance. At the same time, with a thermal expansion coefficient close to that of the third-generation semiconductor substrate silicon carbide crystal, it has become the preferred material for high thermal conductivity substrates in third-generation silicon carbide semiconductor power devices. At present, silicon nitride ceramic substrates are widely used in power modules, heat sinks, LEDs, wireless modules, etc. Driven by the growth in demand for power modules, the sales of silicon nitride ceramic substrates in 2024 are about 136.6 million US dollars, with a compound annual growth rate of about 6.45% from 2018 to 2024.

Ceramic Substrate: Optimal Selection Of High-End Probe Card Core Components

A probe card is a testing interface composed of probes, electronic components, wires, and printed circuit boards (PCBs). Depending on the situation, there may also be requirements for reinforcement boards, mainly for testing bare cores. According to different application scenarios and requirements, probe cards can be divided into various types, such as cantilever probe cards, vertical probe cards, MEMS probe cards, etc. Widely used in integrated circuit testing, semiconductor manufacturing, automotive electronics and other fields.

Ceramic substrate in probe card

The STF substrates are the core component of the entire probe card. The spatial conversion matrix plays a role in electronic connection spacing conversion and electrical signal transmission throughout the probe card, while providing sufficient mechanical/mechanical strength to support the applied force of several hundred to several thousand Newtons during the testing process.

The adapter board in high-end probe cards often uses ceramic substrates. Precision ceramic substrates have excellent electrical insulation, high thermal conductivity, high adhesion strength, and large current carrying capacity. And it has high strength, high hardness, and a wide temperature range, which can reach -55 ℃ to 850 ℃. The coefficient of thermal expansion is close to that of silicon chips. In a multi temperature testing environment, it is one of the effective solutions to solve deformation.

The ceramic substrate used for probe cards is generally a single-layer or multi-layer ceramic substrate with metallization. The multi-layer ceramic substrate is made by co firing high-temperature or low-temperature ceramics through multi-layer lamination and co firing, commonly referred to as a multi-layer ceramic space conversion matrix (MLC).

Type of ceramic substrate material for probe cards

1. High alumina porcelain

High alumina porcelain is a ceramic material mainly composed of aluminum oxide. It has excellent electrical performance and high-temperature stability, so it has been widely used in probe cards. High alumina ceramics have high strength and hardness, but high brittleness. Therefore, in the manufacturing process, it is necessary to pay attention to controlling process parameters such as sintering temperature and time.

2. Silicon nitride ceramics

Silicon nitride ceramic is a ceramic material mainly composed of silicon nitride. It has excellent electrical performance, high temperature stability, and oxidation resistance, so it can replace high alumina porcelain as a substrate material in some application fields. Previously, Kyocera launched a Starceram N3000 P high-performance silicon nitride ceramic plate, which combines the necessary strength, low wear, and the ability to slide back and forth in the guide hole, with the best characteristics suitable for producing probe cards.

3. Other material types

In addition to high alumina ceramics and silicon nitride ceramics, there are also some other types of materials that can be used to manufacture ceramic substrates for probe cards. For example, magnesium oxide ceramics have excellent electrical properties and high temperature stability; Boron nitride ceramics have excellent high-temperature resistance and oxidation resistance; Silicon carbide ceramics have excellent characteristics such as strength and hardness. These material types can also be applied in certain application fields, but they need to be selected based on specific usage environments and performance requirements.

What Important Role Does Beryllium Oxide Play In The Nuclear Industry

In advanced ceramic materials, toxicity is the inherent “label” of beryllium oxide, and in many applications, beryllium oxide is the first to be excluded. But this ceramic material that talks about color change can conquer a “difficult” industry – the nuclear industry.

Since the first nuclear reactor was established in the United States in 1942, the nuclear industry has been developing for nearly eighty years. During this period, the development center of the nuclear industry shifted from nuclear weapons to nuclear energy applications, and the materials used in the nuclear industry were constantly being updated. Among them, ceramic materials for nuclear reactors are one of the important materials used in reactors. In reactors and fusion reactors, ceramic materials receive high-energy particles and γ Radiation from radiation, therefore, in addition to high temperature and corrosion resistance, ceramic materials also need to have good structural stability. The fission reaction in a nuclear fission reactor is caused by neutron bombardment of 235U. In light water reactors, heavy water reactors, and high-temperature gas cooled reactors, slow neutrons are more likely to cause 235U fission compared to fast neutrons produced by neutron fission. Therefore, materials that can slow down neutron velocity are needed in these reactors, which are called moderators. At present, the commonly used moderators internationally include water, graphite, beryllium, beryllium oxide, etc. Among them, beryllium oxide as a ceramic material is considered as a future moderator.

Beryllium oxide is a refractory material that is very stable and dense. Its high temperature vapor pressure and low evaporation rate can be used for a long time in an inert atmosphere, even if the temperature reaches 2000 ℃. However, due to the reaction between beryllium oxide and water vapor to generate beryllium hydroxide, it evaporates significantly when the temperature reaches 1800 ℃ in an oxidizing atmosphere, and a large amount of volatilization occurs when the temperature reaches 1500 ℃ in water vapor. The main performance of BeO ceramic pellets differs from theory. It is worth noting that as the temperature increases, the specific heat capacity of BeO increases sharply, the thermal conductivity decreases sharply, and the coefficient of thermal expansion slightly increases.

In terms of mechanical strength, BeO is about 1/4 of Al2O3, but it has good high-temperature strength. In addition, BeO has good nuclear performance, strong neutron deceleration ability, and high penetration ability for X-rays. At high temperatures, BeO only reacts weakly with carbon, silicon, and boron.

In addition, ceramic particles formed by beryllium oxide and uranium oxide can be combined to form a new type of nuclear fuel. In nuclear fuel neutron source assemblies, both initial and restart of the reactor require a neutron source to “ignite”. Polonium (PO) beryllium source is commonly used in primary neutron source rods, while antimony beryllium source is commonly used in secondary neutron source rods. Currently, the Korean Nuclear Research Institute uses beryllium oxide ceramics to act on the startup control rods of primary neutron source reactors, which is very rare.

In addition, compared with graphite materials, beryllium oxide ceramics have excellent comprehensive properties such as oxidation resistance, corrosion resistance, high thermal conductivity, better neutron slowing and breeding ability, and are expected to play important roles as structural materials, moderators, and matrix materials in small nuclear reactors for deep-sea deep space exploration, land-based mobile nuclear power, and thermonuclear propulsion in the future.

Common Materials, Characteristics, And Accuracy Levels Of High-End Ceramic Balls

In the development and application process of engineering ceramic products, ceramic ball bearings are a typical example of the widespread application of engineering ceramics in the industrial field. Ceramic ball bearings have excellent comprehensive performance such as long service life (2-5 times that of steel bearings), high speed, good overall accuracy and stiffness, good thermal stability, and no magnetism. They have a very broad application prospect in working conditions such as high temperature, high speed, high precision, acid alkali corrosion, electrical corrosion, strong magnetic field, no lubrication or medium lubrication. In high-speed precision ceramic ball bearings, the most commonly used is hybrid ceramic ball bearings, where the ball is made of ceramic balls and the bearing ring is still made of steel. This type of bearing has a relatively high degree of standardization and will not make significant changes to the machine tool structure, making it easy to maintain and especially suitable for high-speed operation. The assembled high-speed electric spindle has advantages such as high speed, high stiffness, high power, and long service life.

Compared with traditional bearing steel, precision ceramic balls have excellent comprehensive properties such as low density, high hardness, high elastic modulus (stiffness), wear resistance, low coefficient of thermal expansion, good thermal and chemical stability, insulation, and no magnetism. Silicon nitride is considered the best material for manufacturing bearing rolling elements and has achieved great success in the application of ceramic ball bearings. Ceramic ball bearings can operate without adding any grease, avoiding the occurrence of premature bearing damage caused by grease drying in ordinary bearings. At present, ceramic balls have been widely used in various fields such as aerospace, military, petroleum, chemical, and high-speed precision machinery.

1. Common materials and characteristics

The ceramic balls used in the market mainly include silicon nitride ceramic balls (Si₃N₄), zirconia ceramic balls (ZrO₂), silicon carbide ceramic balls (SiC), and high-purity alumina ceramic balls (Al₂O₃ ). Si₃N₄ has become the most widely used variety due to its superior comprehensive performance. The reason why precision ceramic balls can replace steel balls is that they have characteristics such as low density, medium elastic modulus, low thermal expansion coefficient, and excellent internal chemical properties. The most important feature is that their failure mode, like bearing steel, occurs in a pre existing peeling mode, while ZrO₂ and Al₂O₃ both occur in a destructive failure mode such as fragmentation. Therefore, ZrO₂ and Al₂O₃ are relatively less applied. The following table provides a brief comparison of the main properties of the four materials.

Table 1- Performance Comparison of Four Materials

A. Silicon Nitride Ceramic Balls
Silicon nitride ceramic material has light weight, fine surface, high moisture content, wear resistance, high toughness, high temperature resistance of 1400 ℃, and is not easily deformed. Compared to ZrO₂ material, Si₃N₄ all ceramic bearings are suitable for higher speeds and load capacities, as well as for higher ambient temperatures. The thermal expansion coefficient of silicon nitride ceramics is only 1/4 of that of bearing steel, reducing the sensitivity of bearings to temperature changes and helping to prevent jamming. At the same time, it can be used as a precision ceramic bearing for high-speed, high-precision, and rigid spindles, with a maximum manufacturing accuracy of P4 to UP levels.

B. Zirconia Ceramic Balls
Zirconia ceramics are not oxidized, not easily corroded, non magnetic, resistant to high temperatures of 1000 ℃, not easily deformed, and have a thermal expansion coefficient similar to that of metals in the industrial environment, but have weak resistance to strong acid and alkali corrosion. The density per cubic centimeter can reach as high as 5.95-6.05g/cm³. Among the four commonly used materials for making ceramic spheres (Si₃N₄, SiC, Al₂O₃, ZrO₂), zirconia ceramics have a higher toughness, reaching over 10MPa · m^1/2. The thermal expansion coefficient is close to that of metals, which can meet the needs of good bonding with metals. Zirconia ceramics have self-lubricating properties, which can solve problems such as pollution caused by lubricating media and inconvenience in addition; Good corrosion resistance, can also be used in medium acid, medium alkali, seawater and other media; High temperature resistance, zirconia ceramics have almost no change in strength and hardness at 600 ℃; Non magnetic, insulating, and can also be used in magnetic fields. However, dimensional stability varies greatly with temperature, and the form of rolling fatigue contact failure is destructive fragmentation, which is not as stable as silicon nitride materials in some critical situations.

C. Silicon Carbide Ceramic Balls
Silicon carbide ceramics have the highest usage limit temperature, high strength at high temperatures, highest thermal conductivity, best thermal shock resistance, highest elastic modulus, and lowest density among the four types, and have the best corrosion resistance. They can withstand a mixture of concentrated hydrofluoric acid and heated strong acids, and can be used in extremely strong corrosion resistant environments.

D. Alumina Ceramic Balls

The main component of alumina ceramic balls is high-quality alumina, with a bending strength of up to 250MPa. Hot pressed products have a bending strength of up to 500MPa, and have excellent wear resistance. They are widely used in the manufacturing of grinding wheels, ceramic nails, bearings, etc.

2. Precision level of ceramic balls

The accuracy of ceramic balls has been graded in the market, and Table 3 and Table 4 respectively list the explanations of professional evaluation standard terms and international general grade standards. Ceramic balls usually have an accuracy of G100 or higher for bearings, and between G3-G20 for high-precision bearings.

Table 2 Important Indicators of Precision Level

Table 3 International Standard (ISO3290-1:2014) (Unit: μ M)

The Mechanism of Grinding Fluid in Precision Machining of Silicon Nitride Ceramic Balls

With the continuous investment of high-power grid connected wind turbines from various countries around the world and the vigorous development of aerospace industry, the demand for silicon nitride ceramic bearing balls is strong in both domestic and international markets.

The reason why it can be applied in the above fields is because silicon nitride ceramic materials have high hardness, wear resistance, low density and thermal expansion coefficient, excellent high temperature resistance, non magnetism, corrosion resistance, high thermal conductivity, self-lubrication, and excellent thermal shock resistance, oxidation resistance, and many other characteristics. Therefore, it is the preferred material for bearing balls working in high temperature, high-speed, high-precision, and special environments.

Note: Si3N4 is an inorganic substance with high hardness, lubricity, and wear resistance. The Si-N4 tetrahedral structural unit is formed by covalent bonding of 1 Si atom and 4 N atoms, and the tetrahedral unit forms a three-dimensional spatial network. The special structure makes the hardness of silicon nitride material very high, with a Mohs hardness of about 9. Therefore, the material performance of silicon nitride material can remain stable at high temperatures of 1400 ℃.

1. The Spheroidization Principle of Silicon Nitride Ceramics

At present, there are roughly two types of mechanical grinding and polishing methods for ceramic balls: one is the cup shaped grinding tool processing method, which is characterized by the ability to continuously change the rotation angle of the ball and high processing accuracy. However, only one ball can be processed at a time, and is often used to produce high-precision balls in standard balls and positioning systems. Another type is the grinding disc processing method, which is currently the main method for producing ceramic balls. It can process thousands of balls at once, with high efficiency but low accuracy. In addition to mechanical polishing, new technologies for ultra precision machining of ceramic balls such as magnetic fluid polishing, chemical mechanical polishing, and ultrasonic assisted polishing have also emerged in recent years. By adopting these new “flexible” machining techniques, micro cutting of ceramic ball surface materials can be achieved, allowing for the removal of allowances through plastic fracture, thus obtaining a super smooth and undamaged surface.

However, regardless of the grinding and polishing method, the basic principle is to achieve efficient material removal through abrasive particles and grinding fluid. Under the action of abrasive particles and grinding fluid, the processing deterioration layer of the sphere gradually decreases or is removed, resulting in a smooth or ultra smooth sphere. As a hard brittle material, ceramic balls have high requirements for various components in the grinding fluid due to their low surface energy The main components and functions of grinding fluid
Silicon nitride ceramic balls belong to hard brittle materials, and their processing techniques mainly include mechanical grinding processing technology, chemical grinding processing technology, and chemical mechanical grinding processing technology. These grinding methods all require grinding fluid to assist in processing, which can remove materials and also provide surface finishing treatment for the workpiece.
The selection of grinding fluid has a significant impact on the efficiency and accuracy of grinding processing, and its role is different in the coarse and fine grinding stages. The coarse grinding stage focuses on improving grinding efficiency, while the fine grinding stage improves grinding accuracy. Grinding fluid is mainly composed of abrasive particles, grinding base fluid, and additives. During the grinding process of ball billets, abrasive particles act as cutting tools and can remove surface allowances. The hardness and size of abrasive particles affect processing efficiency and accuracy; The base liquid is the carrier of abrasive particles and needs to meet the requirements of sufficient suspension of abrasive particles; Additives are mainly used to assist in abrasive grinding and improve the grinding environment. The main functions of each component in the grinding fluid are as follows.

01). The role played by abrasives

(1) Grinding action
Radial cracks are subjected to a force directed towards the interior of the workpiece, which can develop towards the interior and damage the workpiece, reducing the original hardness of silicon nitride materials. However, this phenomenon does not develop rapidly. As a brittle material, silicon nitride ceramic balls can also be removed through plastic removal under certain processing conditions. The critical condition for brittle removal can be calculated through the indentation fracture mechanics model. When this condition is lower than the critical condition for brittle removal, the material removal of silicon nitride ceramic balls is mainly plastic removal, and the critical condition is related to the compressive load and the hardness of the abrasive particles. Therefore, When the pressure load is determined, the abrasive particles in the grinding fluid will have a certain impact on the grinding effect of silicon nitride ceramic balls, so the selection of abrasive particles in the grinding fluid is very important.
In addition, chemical reactions may occur during the grinding process, which can change the properties of the surface material of silicon nitride ceramic balls, converting the harder silicon nitride material into silicon dioxide material, thereby reducing the hardness of the ball surface, achieving better material removal effect, and improving the surface quality of the processed parts.
In terms of abrasive selection, if you want to have the best effect on the workpiece, you must choose abrasive particles that have high hardness, high strength, good toughness, high stability, chemical stability, and self sharpening properties when selecting abrasive particles. Generally speaking, the hardness of abrasive particles must not be lower than the hardness of the workpiece being processed, otherwise it is impossible to effectively grind the workpiece. However, it should not be too high, as high hardness often leads to wear of the grinding tool and shortens its lifespan.
For the grinding process of high hardness silicon nitride ceramics, carbide abrasive particles and diamond like abrasive particles are generally selected. Silicon carbide has the characteristics of high hardness, high strength, good chemical stability, and good thermal stability, making it the most commonly used material in ceramics. Silicon carbide can maintain its chemical properties under high temperature, high pressure, strong acid, and strong alkali conditions, and has a relatively small friction coefficient, so its wear resistance is relatively good. Diamond has the characteristics of high hardness, high melting point, and low friction coefficient, which are also suitable for grinding silicon nitride ceramics. However, diamond is expensive, and considering economic issues, diamond abrasive particles can be used for ultra precision grinding.

2. Role played by liquid phase medium

(1) Lubrication effect
After the surface material of silicon nitride ceramic balls is removed, the debris is dispersed in the solution, which has a significant impact on the surface quality of the ball. However, the lubrication effect of the grinding fluid can form a lubricating film between the ball and the debris, improving the rotation or rolling efficiency of the ball. The surface of the ball is protected, which helps to improve the efficiency of grinding processing and can improve the material removal rate while avoiding damage. The base fluid in the grinding fluid is the main lubricating medium, and boundary lubrication is achieved through the action of water. When in contact with the surface of the workpiece, adsorption and reaction films are formed, which can effectively protect the workpiece and improve its rotation ability.
There are two main types of adsorption membranes, namely physical adsorption membranes and chemical adsorption membranes. The physical adsorption film is mainly formed by the van der Waals force between particles in the grinding fluid, which attracts each other and exists in low load and low speed grinding environments; The chemical adsorption film is mainly formed by the chemical reaction between polar molecules in the grinding fluid, and exists in high temperature, high load, and high speed grinding environments, which can effectively protect the surface of the workpiece.
(2) Cooling effect
The cooling effect of grinding fluid refers to the ability of the grinding fluid to absorb the heat generated by the mutual compression between the ball and abrasive particles during the processing, reducing the temperature of the ball surface and avoiding problems such as surface damage caused by excessive temperature. The grinding fluid flows through the processing area, taking away processing heat through the fluidity of the fluid and liquid vaporization, reducing the temperature of the processing area and protecting the processed parts. The temperature of abrasive particles in the processing area will also increase. In order to ensure the self sharpening performance of abrasive particles and enhance grinding efficiency, it is necessary for the grinding fluid to have good cooling performance.
The cooling performance of the grinding fluid is influenced by the thermal parameter values and flowability, and the thermal parameter values in the grinding fluid are determined by the specific heat capacity and thermal conductivity rate; The fluidity of a liquid is mainly determined by its permeability, which depends on the surface tension and viscosity. When the surface tension is high, the grinding fluid on the surface of the ball will become a droplet like liquid. At this time, the contact angle between the solution and the surface of the ceramic ball is large, which weakens the permeability of the grinding fluid and reduces its cooling ability; When the surface tension is low, the grinding fluid on the surface of the ball will be evenly dispersed. At this time, the contact angle between the solution and the surface of the ceramic ball is small, and the permeability of the grinding fluid is enhanced, making its cooling ability stronger.
(3) Suspension effect
There is a certain interaction between abrasive particles, which can affect the form of abrasive particles in the grinding fluid. There are mainly two different forms: one is agglomeration form, and the other is dispersion form. There are three main types of interactions between abrasive particles, namely electrostatic interactions, van der Waals interactions, and steric hindrance interactions.
The dispersion effect of abrasive particles in the grinding fluid is mainly determined by the base liquid. When the base liquid medium shows hydrophilicity, hydrophobic substances will have a certain repulsive effect on water, leading to agglomeration and precipitation. Therefore, hydrophilicization treatment should be carried out on it. When dispersing abrasive particles in the grinding fluid, it is necessary to make a judgment on the physical properties of the abrasive particles. The size and hydrophobicity of the abrasive particles will have a certain impact on the dispersion effect of the grinding fluid. There are many dispersion processes for abrasive particles in the grinding fluid, including mechanical stirring, ball milling dispersion, and ultrasonic dispersion. Among them, ultrasonic dispersion has a better effect, and the distribution of abrasive particles in the grinding fluid is relatively uniform, resulting in higher stability of the grinding fluid.
(4) Cleaning effect
The chips generated during the processing of silicon nitride ceramic balls are not cleaned in a timely manner, and the chips stay between the workpiece and abrasive particles for a long time, or adhere to the surface of the workpiece. This not only scratches the surface of the ball, but also affects the processing efficiency. By adding some surfactants to the grinding fluid to enhance its cleaning ability, these additives can reduce the adhesion ability of debris and prevent it from being carried away by the flowing grinding fluid, thus avoiding damage to the surface of the workpiece. The cleaning ability of grinding fluid is related to the fluidity and pressure supply of the liquid. When the fluidity of the grinding fluid is strong, the cleaning ability will also be enhanced. For example, the cleaning effect of grinding ceramic balls with water medium is greater than that of grinding with oil medium.

3. Summary

The dimensional accuracy and surface quality of ceramic balls have a significant impact on the lifespan of bearings, and in order to pursue dimensional accuracy and surface quality, it is necessary to pay attention to the selection of grinding fluid. By analyzing the main components and functions of the grinding fluid, a more targeted design of the polishing fluid formula can be achieved, which will be of great significance for the development of efficient and low-cost ceramic ball grinding polishing fluids.

Silicon Nitride Ceramic Substrate: A Blue Ocean For Future High-Performance Power Module Designers

With the significant improvement of the integration and power density of the third-generation semiconductor SiC power devices, the corresponding heat generated during operation has sharply increased. Therefore, the heat dissipation problem of electronic packaging systems has become a key factor affecting their performance and lifespan. To effectively solve the heat dissipation problem of devices, it is necessary to choose high thermal conductivity substrate materials.

According to statistics, the failure rate of high-power devices caused by heat is as high as 55%. Moreover, in fields such as new energy vehicles and modern transportation tracks, complex application conditions such as bumps and vibrations need to be considered during the use of high-power devices, which puts higher demands on the mechanical properties and reliability of materials such as substrates. Silicon nitride performs best in terms of comprehensive performance, which is undoubtedly a very ideal substrate material with good heat dissipation performance.

Silicon nitride, the “full mark” material in the heat dissipation substrate

1. Full score for comprehensive performance
Compared to other materials, ceramic substrates have better performance, so choosing ceramic materials as substrates will have broader prospects. At present, the main ceramic materials that can be used as substrates include AlN, Al₂O₃, SiC, BeO, Si₃N₄, etc. Although BeO ceramic substrates have high thermal conductivity and low dielectric constant, their powders are toxic and harmful to health, and are currently rarely used. SiC has stable properties, but its dielectric loss is high and its breakdown voltage is low, making it unsuitable for high-voltage working environments. Al2O3 ceramic substrates have the longest and most mature application history, but due to their low theoretical and practical thermal conductivity, they cannot meet the heat dissipation requirements of large circuits and can only be used in small circuits. Compared to AlN ceramics, AlN ceramics have the characteristics of high thermal conductivity, good insulation, and low dielectric constant. However, AlN also has shortcomings that cannot be ignored, including easy hydrolysis of the material, insufficient strength and toughness, and fragility. Therefore, there is an urgent need for a more stable ceramic material to compensate for the limitations of AlN.

Material performance comparison

Compared with other materials, silicon nitride ceramics are recognized as the preferred material for high thermal conductivity ceramic substrates due to their high thermal conductivity (the thermal conductivity of their crystals can reach up to 320W · m^-1 · K^-1), low dielectric constant, non-toxicity, and matching thermal expansion coefficient with single crystal Si.

2. Demand trend “plus points”
With the increasing demand for performance, alumina (Al₂O₃) or aluminum nitride (AlN) ceramic materials are no longer outstanding in power templates, and more and more designers are considering using advanced substrate materials to replace them. For example, in the application of new energy vehicles (xEVs), when the chip temperature rises from 150 ° C to 200 ° C, its switching loss will be reduced by 10%. In addition, new packaging technologies such as welding and lead-free modules also place higher demands on materials.
Increasing the service life in harsh environments is also another driving factor for ceramic material iteration. For example, wind turbines have an expected service life of 15 years under all environmental conditions, during which they will not malfunction. Therefore, designers of wind turbines are also attempting to improve substrate technology. The third driving force for improving substrate products is the use of silicon carbide components (SiC). Compared with traditional modules, the first batch of modules using silicon carbide and optimized packaging technology reduced losses by 40% to 70%, but the latter requires the use of new packaging methods such as silicon nitride (Si₃N₄) substrates. The above trends will limit the future use of traditional aluminum oxide and aluminum nitride substrates, while silicon nitride based substrates will become the best choice for high-performance power module designers in the future.

Solving the Problem of Mass Production of High Performance Silicon Nitride Substrates

Although silicon nitride ceramic substrates are recognized as the best heat dissipation substrates with comprehensive performance, there are two thorny challenges that need to be solved in actual production, namely achieving “high thermal conductivity” and “sustained and stable mass production”.
To achieve “high thermal conductivity”, high-quality silicon nitride powder and scientific and advanced preparation technology are indispensable. In terms of raw materials, high-quality silicon nitride powder ensures the “excellent gene” of silicon nitride substrate at the source. The particle size, purity, and phase of the raw material powder are key factors affecting the mechanical properties and thermal conductivity of high thermal conductivity silicon nitride ceramics. Internal impurities and lattice defects can hinder the improvement of thermal conductivity of silicon nitride ceramics, so it is necessary to choose high-purity and high silicon nitride raw materials. In addition, the morphology of raw material powders is also very important. Powders with small initial particle size, large specific surface area, and “self formed” crystals have good sintering activity, making it easy to prepare high-density finished products.
For silicon nitride substrates, continuous and stable mass production is an industry challenge. It requires stable processes that can ensure that the substrate avoids warping, cracking, and other phenomena, as well as efficient continuous operations.

Market Prospects for Silicon Nitride Ceramic Substrates

With the rapid promotion of third-generation semiconductor chips based on SiC in new energy vehicles and 5G, the demand for silicon nitride ceramic substrates has also entered a rapid development stage. It is predicted that the global annual sales volume of electric vehicles will exceed 25 million in 2025. The proportion of SiC power devices is based on 37% of the estimated data from multiple investment institutions, and the existing Si3N4 ceramic substrate for electric vehicles is used as a standard chip (7.5 × Based on the usage of 2 standard pieces per vehicle for large vehicles such as buses, the global annual demand for high thermal conductivity silicon nitride substrates in 2025 is approximately 600000 square meters.
This is only a market forecast in the field of new energy vehicles. In addition, the demand for high-performance silicon nitride ceramic substrates in fields such as charging systems and LEDs is also rapidly increasing.

Conclusion

With the rapid development of electric vehicles and high-power electronic power devices, Si₃N₄ ceramic substrates will inevitably face huge market demand. China should further strengthen the collaborative cooperation among universities, research institutes, and enterprises in this field, focusing on breakthroughs in key technologies and equipment for the industrialization of high thermal conductivity Si₃N₄ substrates, fully opening up the Si₃N₄ substrate precision processing surface copper coating assessment application industry chain, and achieving the large-scale localization of high thermal conductivity Si₃N₄ substrates as soon as possible.

Why is the demand for silicon nitride ceramic bearing balls skyrocketing? What are the advantages of Si₃N₄?

Silicon nitride (Si₃N₄) is a strong covalent bond compound composed of silicon and nitrogen, which has been widely produced as a ceramic material. As a typical covalent bond ceramic material, the core challenge in the development and application of silicon nitride ceramics is the sintering densification of the product. Therefore, it is necessary to add a certain amount of sintering aids to complete the densification process through liquid phase sintering. By adding different sintering aids and using different sintering processes, silicon nitride ceramic materials with different comprehensive properties can be prepared. Silicon nitride has excellent wear resistance, corrosion resistance, high temperature resistance (bending strength can reach over 350MPa at 1200 ℃), and thermal shock resistance due to its covalent bonding method. At the same time, the unique interwoven microstructure of silicon nitride columnar crystals endows silicon nitride ceramics with higher toughness, making them widely used in fields such as aerospace, national defense, military industry, and machinery.

Among the various applications of silicon nitride ceramics, bearing balls are the most widely used, accounting for three tenths of the world”s high-performance silicon nitride products in annual production. Compared with traditional steel balls, silicon nitride ceramic bearing balls have excellent properties such as low density, high temperature resistance, self-lubrication, and corrosion resistance. They are mainly used in fields such as precision bearings for machine tools, automotive bearings, insulated bearings for wind turbines, corrosion resistance and high temperature resistance bearings in petrochemical industry. In addition, due to the insulation properties of silicon nitride shafts, they are very suitable for applications in fields such as electric vehicles.

With the development of high-end equipment manufacturing industry and new clean energy, especially the wind power generation industry and aerospace industry, the usage of insulated bearings and spindle bearings used in wind turbines, as well as bearings used in aerospace engines, has significantly increased. The demand for silicon nitride ceramic bearing balls used in conjunction with them is strong.

According to incomplete statistics:

In 2019, the total global consumption of silicon nitride bearing balls reached 470 million US dollars,
In 2020, the total global consumption of silicon nitride bearing balls reached 510 million US dollars,
In 2021, the total global consumption of silicon nitride bearing balls reached 550 million US dollars, a year-on-year increase of 7.8%.
Future: With the continuous growth of demand in new energy vehicles, wind power and other fields, the market space for silicon nitride ceramic bearings is expected to further expand.

Stable Growth in the Global Argonized Silicon Bearing Ball Market

Global market size of silicon nitride bearing balls (100 million US dollars)

Bearing balls are one of the main applications of silicon nitride ceramics and have many advantages compared to traditional steel balls.

Silicon nitride ceramics are mostly composed of atomic crystals, with atoms connected by covalent bonds. Compared to metal bonds, covalent bond energy is higher, resulting in higher hardness, corrosion resistance, stable chemical properties, but poor toughness of ceramics. There is a free electron cloud near the metal bond, which does not exist in atomic crystals. Therefore, compared to metals, ceramics have stronger insulation ability and do not have conductivity.
The hardness of silicon nitride ceramics is more than twice that of steel balls, but the thermal expansion coefficient is less than one-third of that of steel balls, and the working temperature can reach 1000 ℃.

The most widely used sintering processes for silicon nitride ceramic balls are hot isostatic pressing (HIP) and gas pressure sintering (GPS), and the ceramic balls produced under these two processes are widely used in different usage environments. Among them, HIP sintering can completely densify silicon nitride ceramic balls, significantly reduce defects, and greatly improve various mechanical properties; GPS sintering can prepare products with good performance and complex shapes at a lower cost, and achieve mass production in industry.

Random Talk on “Kiln Furniture” – “Behind the Scenes Workers” in the Ceramic and Lithium Battery Industries

With the rapid development of industry, kiln furniture, as a special refractory material, has become an essential high-temperature auxiliary material product in the sintering process of ceramics, lithium battery and other industries.

Kiln furniture refers to refractory products that are recycled in industrial kilns to support or protect burned products. It is widely used in the production of daily ceramics, architectural ceramics, sanitary ceramics, and advanced ceramic materials. In recent years, with the rise of the new energy market, lithium battery positive electrode materials require a large number of high-performance kiln furniture in the production process, which has further attracted attention to kiln furniture.

In the process of use, kiln furniture is generally thinned to reduce heat storage and save energy, but it also needs to have a certain load-bearing capacity, so kiln furniture needs to have high room temperature and high temperature strength; The rapid firing process of ceramics requires kiln furniture to have better thermal shock resistance; For electronic ceramics, in order to prevent product contamination, it is required that the kiln furniture have good chemical stability; Modern industry requires kiln furniture to have precise dimensions during mechanical operation to ensure normal production.

1、 Structural kiln furniture

Structural kiln furniture is an important component of industrial kilns. When in service, the temperature inside the furnace is high, and it is directly in contact with gas flames or radiated by heating elements for heat transfer. It usually bears more weight than itself, or even several times its weight without deformation or fracture. This requires it to have a certain degree of high-temperature mechanical strength and good thermal shock stability. In this type of kiln furniture, the main types are shed boards (beams and columns are usually used in conjunction with shed boards, represented by shed boards), push boards, and roller bars, with a large market capacity.

The application of pusher plate kilns in the ceramic industry is relatively common, with pusher plates being its basic accessory material. Usually, the performance of pusher plates determines the operational efficiency of the kiln. When the pusher kiln is running, it is required to withstand the load of the ceramic body or saggers, huge jacking force, and frictional resistance with the track without fracture at high temperatures. The cold and hot cycle service life can reach dozens or even hundreds of times. Therefore, the pusher kiln must have high room temperature, high temperature strength, wear resistance, and excellent thermal shock stability.

Traditional refractory materials such as corundum and mullite have many advantages, such as high load softening temperature and good creep resistance. However, pure corundum products have less ideal thermal shock resistance due to their high thermal expansion coefficient. The thermal expansion coefficient of mullite material is significantly lower than that of corundum, and it can be used as a secondary crystal or bonding phase in products. Therefore, corundum mullite based pusher plates combine the properties of both materials, especially the significantly improved thermal shock resistance compared to corundum based products. When used in pusher plate kilns for firing high-temperature ceramic materials, their service life can reach over 100 times.

Kiln uses the rotation of the rod to transport the billet, gradually completing the sintering process through preheating, sintering and cooling each belt. The advantages of a roller kiln are that the temperature inside the kiln is evenly heated up and down by the stick, the product firing cycle is short, and the fuel consumption is low. Ceramic rollers are key components of roller kilns and require a significant amount of consumption. It plays a load-bearing and transmission role in the continuous high-temperature firing of products. When used, it must not only be resistant to high temperature, but also have the characteristics of resisting high-temperature creep during long-term rotation. Ceramic rollers are mainly made of corundum, aluminosilicate, fused silica and silicon carbide. The materials of the silicon carbide roller rod include recrystallized crystal and reaction sintered silicon carbide.

2、 Sintered vessels (saggar, crucible, plate)

A specialized kiln tool that supports the firing of ceramic bodies, or a saggers that holds powders (such as positive electrode materials, magnetic powders, high-purity ceramic materials, etc.) and then undergoes heat treatment in roller kilns, pusher plate kilns, and tunnel kilns. Depending on the firing process used by the manufacturer, this type of kiln tool will withstand different heating conditions. The material of this type of product depends on the type of sintered body and the heat treatment process.

Contains powders (lithium battery positive electrode materials, magnetic powders, high-purity ceramic powders) and undergoes heat treatment in a roller kiln, pusher plate kiln, or tunnel kiln. It is generally formed using extrusion, machine pressing, pouring, and isostatic pressing processes, and suitable forming processes are selected based on the composition and structure of the product. The most widely used materials include cordierite mullite, corundum mullite, silicon carbide, and graphite, with lithium ion cathode materials being the most commonly used in the synthesis field.

Cordierite mullite saggers is widely used in the field of positive electrode materials for lithium batteries due to its excellent thermal shock resistance and economy.

The cordierite mullite crucible is based on lithium carbonate/lithium hydroxide, which has strong alkalinity, low melting point, and strong corrosiveness to acidic refractory materials. The lifespan of aluminum silicon based saggers is generally lower. Corundum based saggar is mainly used for the calcination of high-purity powders in environments with low thermal shock conditions and high operating temperatures, such as high-purity aluminum oxide powder. The saggar needs to be fired at a high temperature of 1800 ℃, and is produced using aluminum oxide active powder with 99.9wt% Al2O3 content and low sodium white corundum. The binder uses low ash content (Ash ≤ 0.01wt%) to ensure effective impurity control in the entire raw material control, And achieve a lower coefficient of thermal expansion through sufficient high-temperature firing.

Graphite and silicon carbide saggers have high thermal conductivity, high temperature resistance, excellent thermal shock resistance, and poor oxidation resistance. However, they have excellent alkali corrosion resistance in reducing atmospheres. Graphite saggerss are commonly used as containers for loading high-temperature sintered materials under reducing atmosphere, and are used for sintering lithium iron phosphate and electromagnetic materials. Traditional graphite saggerss= are produced through machining, with low efficiency and high cost. Silicon carbide saggers are widely used in industries such as pharmaceuticals, fine chemicals, engineering metallurgy, and acid pickling.

When the setter/ceramic plate is in service, it needs to withstand the thrust during movement and the friction during product loading and unloading. It does not crack during cold and hot cycling. Under the condition that the thermal shock resistance of the setter/ceramic plate meets the requirements, improving the bending and cracking resistance of the setter/ceramic plate is the key. The material of the fired board requires excellent chemical inertness and does not react with the fired product. The materials of the setter/ceramic plate are divided into aluminum oxide, zirconia, composite, etc., mainly used in the fields of electronic ceramics, special ceramics, etc.

Corundum fired plate refers to the main crystal phase α- The high-end kiln furniture of Al2O3 has excellent properties such as high strength, corrosion resistance, high temperature resistance, and wear resistance. It has small deformation at high temperatures (>1650 ℃), but high sintering temperature and poor thermal shock stability. During the firing process of lead zirconate titanate piezoelectric ceramics, the corundum based firing plate faces phenomena such as center warping, surface layer powdering, and peeling.

Many kiln furniture production enterprises apply plasma spraying technology to the preparation process of fired plates, where the intermediate layer of the fired plates is made of corundum mullite material and the outer layer is coated with zirconia fusion coating, which has high thermal shock resistance and does not react or adhere to the fired laminated ceramic capacitors.

Beryllium oxide ceramic – which has made many people turn pale upon hearing, but has great uses

Beryllium oxide is an inorganic compound with a molecular formula of BeO. This colorless solid is a famous type of electrical insulator, with a thermal conductivity higher than any non-metal except for diamonds and surpassing most metals.

But many people turn pale when they hear its name, not a devil, but an angel. BeO has a very obvious drawback, as its powder is highly toxic, and inhalation can cause lung function damage or even poisoning, endangering life, which indeed limits its promotion. However, the potential toxicity hazards during the production process can also be protected and treated, and beryllium oxide made into ceramic products is non-toxic.

BeO has a wurtzite type structure with cubic crystal units and strong covalent bonds. Its thermal conductivity is extremely high. BeO ceramics with a BeO mass fraction of 99% have a thermal conductivity (coefficient of arrival) of up to 310W/(m · K) at room temperature, which is about 10 times that of Al2O3 ceramics with the same purity. At the same time, they also have low dielectric constant and loss, as well as high insulation and mechanical properties. BeO ceramics are the preferred material for high-power devices and circuits that require high thermal conductivity. On the other hand, the high thermal conductivity and low loss characteristics of BeO are so far incomparable to other ceramic materials. In pursuit of higher performance and high value applications such as aerospace and satellite communication, BeO ceramic substrates are still being used.

Thick film beryllium oxide metallized products

Beryllium oxide ceramic substrates or substrates are metallized with thick films through tungsten manganese or molybdenum manganese active metallization methods, and then product circuits are obtained through nickel plating and pattern etching, mainly used in microwave power circuits and integrated circuits. Good weldability, with a tensile strength exceeding 20MPa after nickel plating. The nickel is fired in a reducing atmosphere of around 800 ℃ without bubbles.

Thin film beryllium oxide metallized substrate

Polished beryllium oxide ceramic substrates are sputtered with resistance and conductive thin films. After electroplating and photolithography, a substrate with partial passive components and conductive circuits can be formed, and chips and various chip like components can be mounted. After bonding and interconnection, circuit modules with specific functions can be formed.

Ceramic tiles for collecting electrodes of traveling wave tubes

Mainly used in the current X and Ku band traveling wave tube collectors, it plays an insulation and heat dissipation role. The main characteristics of the product are its complex appearance and high dimensional accuracy requirements. It is pre formed into a cylindrical shape by isostatic pressing and then cut and processed, ensuring the compactness of the tiles while also ensuring the concentricity requirements during the tile installation process.

Attenuating porcelain products

It has the characteristics of high dimensional accuracy, high mechanical strength, small gas release, high thermal conductivity, and good thermal stability, and can be used as an absorbing material in microwave vacuum devices such as multi beam klystrons.

Crucible products

Beryllium Oxide Ceramic Crucibles made of high-purity beryllium oxide material, it can be used as a crucible for melting rare metals and high-purity metals such as Be, Zr, Pt, V, etc., with high thermal conductivity and excellent thermal stability.

At present, beryllium oxide ceramics are still a relatively unfamiliar material in the civilian market, and their excellent performance has not been fully explored and applied. With the rapid development of technology, various high-tech industries urgently need innovative breakthroughs, and materials are crucial for improving product performance. The “all-in-one ability” of beryllium oxide ceramics will eventually shine!