Ceramic Medical Instruments is used in electronic technology in a variety of ceramics, that is, in the electronics industry for the manufacture of electronic components and devices of ceramic materials, generally divided into structural ceramics and functional ceramics. For the manufacture of electronic components, devices, components and circuits in the matrix, shell, fixtures and insulation parts and other ceramic materials, also known as the device porcelain.
1. Generally divided into: electric vacuum porcelain, resistive matrix porcelain and insulation parts.
Functional ceramics: used in the manufacture of capacitors, resistors, inductors, transducers, filters, sensors and other circuits in the role of one or more of the ceramic material, it is divided into: capacitor porcelain, ferroelectric porcelain, pressure Porcelain, semiconductor porcelain and magnetic porcelain.
Ceramic Medical Instruments in the chemical composition, microstructure and electromechanical properties, and the general power of ceramics with the essential difference.
Ceramic Medical Instruments need to have high mechanical strength, high temperature and humidity, anti-radiation, wide dielectric constant range, dielectric loss, capacitance temperature coefficient can be adjusted, high electrical strength and insulation resistance, and excellent aging performance.
Ceramic Medical Instruments according to the characteristics can be divided into: high frequency and ultra high frequency insulation ceramic; high frequency high dielectric ceramic; ferroelectric and anti-ferroelectric ceramics; piezoelectric ceramics; semiconductor ceramics; photoelectric ceramics;
Ceramic Medical Instruments according to the scope of application can be divided into: fixed ceramics; electric vacuum ceramic (mainly used for insulators, structures, substrates, shell and multi-layer wiring, etc.); capacitor porcelain (high frequency or low frequency capacitor medium, doubles as a capacitor, ; Resistance porcelain and so on.
According to the microstructure: polycrystalline; single crystal; polycrystalline and glass phase; single crystal and glass phase.
The use of ceramic materials, high-frequency or ultra-high frequency electrical properties can be made of various shapes of fixed parts.
Ceramic capacitors, vacuum ceramic parts, carbon film resistors, etc., they are in communication, radio, television, radar, instruments, meters and other electronic equipment is an indispensable part, in addition, with the laser, computing, integration, optics, etc. The development of new technologies, the growing use of Ceramic Medical Instruments.
The development of electronic ceramic materials is closely related to the development of physical chemistry, applied physics, silicate physical chemistry, solid physics, optics, electrical science, acoustics, radio electronics and so on, so as to promote the development of electronic technology. Ceramic Medical Instruments also made a considerable progress accordingly.
2. Electronic ceramic raw materials have three requirements:
(1) Chemical composition: purity, type and content of impurities, stoichiometric ratio;
(2) particle size: particle diameter, particle size distribution, particle shape;
(3) structure: crystal morphology, stability, crack, density and porosity.
The particle size and structure mainly determine the density and formability of the green body. Fine particles, the structure is not complete, then the activity (instability, sinterability) the greater, is conducive to sintering.
The raw materials used in the electronic porcelain can be divided into two types: mineral raw materials and chemical products. The mineral raw materials are clay, bentonite, talc magnesite, fluorite and rutile corundum. The chemical products are 80 to 90 percent pure and 95 to 99 %, Analysis of pure 99 ~ 99.9%, spectral pure 99.9 ~ 99.99.
(1) to promote sintering;
(2) Ⅲ Ⅴ or Ⅱ VI impurities can be compensated as the ion price, and improve the electrical properties of the material Powder stability: polycrystalline transition, there are two or more crystalline ZrO2 low temperature monoclinic (low temperature stability), temperature High, 1100 ℃ into tetragonal (high temperature stability); temperature dropped to 1100 ℃ below, into monoclinic system;
The transition brings the volume effect, ZrO2 from monoclinic to tetragonal, with 8% of the volume shrinkage, and the ceramic appears to crack. Doping solid solution or high temperature calcination to stabilize. The α-Si3N4 and α-SiC have good sintering properties than the low temperature stable β-Si3N4 and β-SiC. The former has an open structure and high internal energy, which is favorable for sintering.
Electronic porcelain forming principle: from the blank (mud) to further processing into a green body called the process.
1, the principle: granulation, good mobility, with the material made of grain, into a certain shape of the steel mold, with the help of plug, through the external force can be pressed into a certain amount of green body. Further close between the particles, so that the colloidal molecules and powder between the force to strengthen, leaving the body only a certain degree of mechanical strength.
2, powder stacking density Bulk density refers to the pressure before the powder in the mold in the natural accumulation or appropriate vibration formed by the degree of filling.
(1) Stacking method: equal diameter ball, the density of up to 74.05% (relative) cubic, the density of up to 52.36% vibration, the density of up to 60% of the general porcelain (powder) dry pressure molding, vibration feeding, Can effectively improve the density of the body.
(2) particle size ratio: thickness with coarse particles accounted for 70%, the highest filling rate, the higher the difference between the radius; the higher the filling rate.
(3) Mobility: between the powder, powder and mold wall between the friction is small, the powder flow is good. Granular: ball mill, spray dry or granulated (appropriate ball) shape close to the spherical, good mobility. Vibration, large ball mill, the shape is not rounded, was polygonal, poor mobility.
3, pressurized with the body density.
(1) single pressure: pressure gradient, due to the powder between the powder and die sets, caused by friction resistance. Poor lubrication, the resistance is large, the pressure difference is large. The greater the pressure difference, slender pressure difference.
(2) two-way simultaneous pressure: the upper and lower indenter at the same time into the mold pressure, the actual pressure difference, resulting in body density is only half of the above method.
(3) two-way pressure; first, and then, under pressure, due to the two pressure and pressure transmission is more thorough, is conducive to gas discharge. 1 ~ 3cmhmm or thin sheet billet pressing, often the role of a one-way one-way rapid punching method. Wafer capacitors, fine-tuning capacitor moving film, integrated circuit substrate, can be used fast punching method.
(4) pressure size and body density. The problem of the removal of the gas contained in the bulk porosity must be taken into account. The density of the blank will increase with the pressure and the pressing time before the naturally occurring exhaust channel between the particles is not completely blocked. When the exhaust channel Has been blocked by pressure, the body density will increase with the pressure close to saturation.
4, because the solid powder itself is almost incompressible, has not yet discharged the remaining adsorption gas, and can not find the way to the outside of the body, so the increase in pressure can only make the closed hole compression. After the pressure removal (hour), the closed air hole may re-expand, rebound, but may make the mold of the billet from the layer, cracking or destruction of a good paste the organization, leaving the body mechanical strength. So the pressure is too large, but will bring adverse effects. Elastic failure.
5, the boost speed and holding time.
Boost too fast, holding pressure is too short, so that the gas can be discharged too late to discharge. At the same time the pressure has not yet passed to the depth, external force has been removed, can not achieve the ideal quality of the body.
6, dry pressure molding advantages and disadvantages
(1) the process is simple, easy to operate, small batch trial production, mass production;
(2) short cycle, high efficiency, easy to automate production;
(3) less water content, less glue;
(4) dense, accurate size, burning shrinkage small, high strength.
(1) pressurized equipment, porcelain pieces are large pressure;
(2) mold, each product a set of mold, demanding, complex structure is difficult to suppress;
(3) mold wear, bring pollution;
(4) axial compression, lack of lateral pressure;
(5) powder itself high internal friction by force, the body structure has obvious anisotropy;
(6) is limited to round, flaky electronic components, it is difficult for the complex shape, large-scale production.
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