First, the structure of the jet mill The jet mill consists of the following parts: The main unit is the airflow crushing part. Electromagnetic vibrating feeder and controller feed the main machine. The collector is a cloth bag, which collects the finished product and discharges the gas. Pressure gauges and pressure regulators: control and regulate pressure. Installation of the bottom plate and the pipeline: The above parts are assembled on the bottom plate to form a crusher assembly. Air compressor: Provides a pressure source to the airflow mill mainframe. Filter: Air compressor pressure gas is filtered through a filter to remove moisture and dirt and then passed to the airflow mill main unit. Second, the working principle of the jet mill The strong multi-turbulent flow field formed when the high-speed airflow is sprayed causes the solid particles therein to be deformed and broken during self-collision or collision with the impact plate and the wall. The powder is fed into the feed nozzle by the electromagnetic vibrating feeder, and is injected into the crushing chamber by the compressed air supplied by the feed, and the supersonic flow is formed by the high-speed airflow sprayed from the crushing nozzle, causing collision, shearing and crushing of the cavity in the flow. Wall collision and friction achieve the purpose of pulverizing into fine powder. During high-speed movement and pulverization of the stream, particles of different fineness will produce different centrifugal forces in the swirling airflow. The powder particles of acceptable fineness have greater force than the centripetal airflow. The centrifugal force is brought to the discharge pipe by the exhaust gas flow, and the finished product is collected through the cloth bag, and the larger particles are thrown to the periphery due to the centrifugal force greater than the force of the centripetal air flow, and the pulverization process continues with the high-speed movement of the logistics. Third, the performance characteristics The internal vertical grading device can adjust the particle size of the product, the pulverization granularity is good, the distribution is relatively narrow, the product fineness is uniform, the particle surface is smooth, the shape is regular, the purity is high, the activity is large, and the dispersion is good. It is suitable for pulverizing low-melting and heat-sensitive materials and biologically active products. Because the jet mill is powered by compressed air, the adiabatic expansion of the compressed gas at the nozzle will lower the temperature of the system, so no large amount of heat will be generated during the work. It can be used in series with a multi-stage classifier, so that multiple particle size segments can be formed simultaneously. The equipment is easy to disassemble and easy to clean. It has no dead angle on the inner wall, can be cleaned thoroughly, and can be operated under aseptic conditions. Closed operation, low running noise, can reduce the generation of dust, not only environmental protection, but also less contaminated products. The production process is continuous, the production capacity is large, the degree of automation and automation is high, the control system is simple to operate, and the equipment operation is safe and reliable. Joint operations can be implemented. Because when pulverizing with superheated high-pressure saturated steam, the material can be pulverized and dried at the same time, and can be used as a mixer; while the material is pulverized, it can be sprayed with a solution of the desired concentration to cover the solid fine particles, The coating layer is formed and surface-modified, and therefore, jet milling can be combined with pulverized surface coating and surface modification. Fourth, classification There are several types of jet mills in China: flat jet mill, fluidized bed jet mill, circulating tube jet mill, jet jet mill, and target jet mill. Flat jet mill Flat jet mill Flat airflow mill working principle diagram Fluidized bed jet mill Friend equipment manufacturing fluidized bed jet mill Weifang Zhengyuan Fluidized Bed Airflow Crusher Circulating tube airflow pulverizer Circulating tube airflow pulverizer Jet jet mill Close friend equipment manufacturing spray jet mill Target jet mill Target airflow mill structure schematic Fifth, the jet mill applications in the non-gold mining industry of the genus Airflow pulverization technology is a simple physical comminution of materials. In the pulverization, since there is no other substance doping and the process temperature is low, the original chemical properties of the material can be maintained, and the loss of the heat sensitive component in the material can be reduced. At the same time, the agglomeration of the mineral, metal and the like powder after the air flow pulverization Phenomena, dispersibility and uniformity are superior to those of traditional mechanical methods, making airflow pulverization technology an irreplaceable position in mineral processing. Especially ultrafine jet milling technology is widely used in the deep processing of titanium white powder, talc, wollastonite, kaolin, quartz, graphite, diatomaceous earth, mica, barite, bentonite and the like of non-metallic mineral. However, the design and manufacturing level of China's jet mills is still far from the developed countries. 1, talc The raw materials of the talc ore after coarse crushing and medium crushing are transported to the jet mill for ultrafine grinding, and the milled material is the final product with a fineness of 500-5000 mesh. The main body is ultra-fine grinding into a flat airflow pulverizer. 2, wollastonite The ultra-fine pulverization of wollastonite with flat airflow pulverizer has better selectivity than medium agitating mill, can ensure the complete crystal morphology of wollastonite, and is an effective ultrafine pulverization for preparing high aspect ratio acicular wollastonite powder. equipment. 3, kaolin As a clay mineral for ceramics, papermaking and chemical fillers, kaolin requires high whiteness and brightness. The jet mill is one of the most commonly used ultrafine grinding equipments for kaolin. Its product size is generally 1~5μm. After pre-grinding to reduce the particle size of the mill, this mill can obtain products with an average particle size of less than 1 μm. 4, titanium dioxide Titanium dioxide is used as a pigment and has very high requirements on particle size, particle size distribution and purity. Generally, mechanical pulverizing equipment is difficult to meet his requirements. Therefore, the airflow pulverizer is selected as the final pulverizing equipment for titanium dioxide at home and abroad. The most widely used flat airflow pulverizer. Sixth, the problem that the airflow pulverizer should pay attention to in actual production and application The first is the noise problem. Both research and production practices have shown that the higher the gas flow rate, the finer the product obtained. When ultra-fine products are to be obtained, the speed of the airflow must be supersonic. Noise makes people unable to concentrate, distraction, and often leads to accidents. Due to the special structure of the jet mill itself, very strict requirements are imposed on the structural design of the muffler. At present, multi-stage cyclone separators and large dust removal equipment and auxiliary equipment such as exhaust fans are usually connected at the discharge port. This is followed by the safety of supersonic jet mills for the manufacture of ultrafine powders. Includes may cause respiratory pneumoconiosis and dust explosions. The particle size of the dust obtained by the supersonic jet mill is basically below 5 μm, which is the most harmful to the human body. The probability of a supersonic jet mill shredder operator suffering from pneumoconiosis occupational disease will increase significantly. At the same time, dust is scattered in the air on a large scale, and dust explosion may occur. China's Jiangsu Miyou Powder New Equipment Manufacturing Co., Ltd. is in a leading position in the anti-dust explosion of airflow pulverizers. Seven, development trend The development of information technology, biotechnology and new material technologies puts higher demands on the particle size, purity and particle size distribution of powder products, and saves energy and reduces environmental pollution as much as possible. In order to meet the needs of social production, ultra-fine pulverization technology faces severe challenges. In recent years, great progress has been made in the basic theoretical research of airflow pulverization. However, many aspects need to be improved: Experimental research on the supersonic pulverization flow field needs to be strengthened. The high pulverization speed brings great difficulty to the direct measurement of the flow field, so the research of the test instrument should be strengthened. At present, there are few pulverizing equipments using steam as a working medium, so that there is little research on the influence process of steam on the pulverizer, and the advantages of the steam working medium can be fully utilized to realize the enlargement of the pulverizing equipment. In the establishment of the airflow pulverization parameter optimization model, it is still lacking, which brings difficulties to the perfection and optimization design of the pulverizing equipment. Deepening mixing, drying, granulation, coating and other processes are combined with pulverization. The pulverization of soft materials is a major problem and research focus of the pulverization technology. Therefore, in order to meet the development needs of modern industry, it is extremely urgent to strengthen basic theoretical research and optimize equipment design. Eight, airflow mill related companies (in no particular order) Jiangsu Miyou Powder New Equipment Manufacturing Co., Ltd. Weifang Zhengyuan Powder Engineering Equipment Co., Ltd. Kunshan Qiangwei Powder Equipment Co., Ltd. Shenyang Aircraft Research Institute Powder Company Anqiu Longxiang Machinery Co., Ltd. Shandong Dinkun Machinery Co., Ltd. Yixing Hongda General Equipment Co., Ltd. Shanghai Huasan Powder Equipment Co., Ltd. Yixing Youte Powder Machinery Equipment Co., Ltd. Qingdao Derui Powder Technology Equipment Co., Ltd.
Impedance control has been one of the essential concerns and tough problems in high-speed PCB design. Impedance is the sum of the resistance and reactance of an electrical circuit. The resistance being the opposition to current flow present in all materials. In high frequency applications, controlled impedance helps us ensure that signals are not degraded as they route around a PCB. Resistance and reactance of an electrical circuit have a major impact on functionality, as certain processes must be completed before others to ensure proper operation.
Impedance control technologies are quite important in high-speed digital circuit design in which effective methods must be adopted to ensure the excellent performance of high-speed PCB. The impedance of a PCB is largely determined by some factors, such as trace width, copper thickness, dielectric thickness, dielectric constant. Impedance, generally measured in Ohms. We must control the resistance and reactance of an electrical circuit to ensure the quality of signal in the complex design. For example single-ended impedance 50 ohm ±10%, differential impedance 100ohm ±10%.
Electrical Impedance: A measure of opposition to time-varying electric current in an electric circuit.
Impedance Control PCB is too complicated? No worry! JHYPCB engineers can help you at any time as we have three shifts. Free stack-up and impedance calculations can be offered upon request. We will work with your engineering team at the conceptual level of the PCB design to assist you to get better results in controlling impedance by choosing the suitable laminate and layer stack up.
Why Impedance Control PCB can be shipped timely all the time? As common materials are stored well in JHY PCB warehouse regularly. We have heavy copper thickness, 2oz, 3oz or more. Odd copper thickness H/1 oz, H/2 oz, 1/2 oz. Foil: 1/4 oz, H oz, 1 oz, 2 oz, 3 oz.
If you need order Impedance Control PCB, just make notes in Readme file, and send it together with Gerber, our engineer will take care of it. Have a try!
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What PCB designer Must Know About Impedance Control PCB
Controlled Impedance PCB Meaning
Because of complex processors, USB devices and antennas are printed directly on the circuit board surface. The speed of signal switching on the circuit board increases, and the electrical characteristics of the tracks that transmit signals between devices become more and more important. Therefore, more and more PCB designs need impedance control and testing.
When to Use Controlled Impedance
When a signal must have a particular impedance in order to function properly, controlled impedance should be used. In high frequency applications matching the impedance of PCB traces is important in maintaining data integrity and signal clarity. If the impedance of the PCB trace connecting two components does not match the components` characteristic impedance, there may be increased switching times within the device or the circuit. There may also be random errors.
Please note that we also need special instructions here: In DC circuits there is no reactance and the resistance of copper conductors is typically insignificant. However in high speed AC circuits (those with sharp changes in voltage and/or current) the reactance and thus the impedance can become very significant. This can become critical to a design's functionality because of the effects that changes in the impedance along the signals path from transmitter to receiver will have on the efficiency of power transfer as well as signal integrity. While a circuit`s speed is often expressed as the frequency of the wave form: the critical concern is the speed at which the voltage and/or current is required to change.
What Determines Controlled Impedance?
The characteristic impedance of a PCB trace is typically determined by its inductive and capacitive reactance, resistance, and conductance. These factors are a function of the physical dimensions of the trace, the dielectric constant of the PCB substrate material, and dielectric thickness. Typically PCB trace impedance can range from 25 to 125 ohms. The impedance value generated from the PCB structure will be determined by the following factors:
– Width and thickness of the copper signal trace (top and bottom)
– Thickness of the core or prepreg material on either side of the copper trace
– Dielectric constant of the core and prepreg material
– Distance from other copper features
Impedance Control In PCB Design
The Problem: "A", "B" and "C" signals all reach the component at the same time.
The Solution: Apply Impedance to Circuit "C" to slow the signal enough for the component to first calculate ("A"+B").
Similar with a cable, the signal encounters a change of impedance arising from a change in material or geometry. Part of the signal will be reflected and part transmitted. These reflections are likely to cause aberrations on the signal which may degrade circuit performance (e.g. low gain, noise and random errors). In practice, board designers will specify impedance values and tolerances for board traces and rely on the PCB manufacturer to conform to the specification.
When rise times continue to reduce, inevitability the number of traces requiring impedance control will continue to increase. Where impedance control is needed it is important to control it accurately, calculating it with the most representative cross-section we can create.
Applications of Controlled Impedance
Controlled Impedance should be considered for PCBs used in fast digital applications such as:
– Telecommunications
– Computing 100MHz and above
– High Quality Analog Video
– Signal Processing
– RF Communication
Impedance Control PCB Manufacturing
In order to meet the growing demand of impedance control PCB, PCB manufacturers have invested a lot of money and manpower and material resources in production technology, in order to meet the production requirements of customers.
Due to the difficulty of impedance control PCB production, PCB manufacturers generally require PCB designers or purchasers to provide more detailed information and requirements, such as the type of material required, copper weight and thickness of the board, the number of layers, gerber file, so that the manufacturer can prepare the bill of materials (BOM). Impedance information should be clearly marked in Gerber file. If the necessary information is lacking, even a little key information will make it difficult or impossible for the manufacturer's engineers to know exactly what the customer needs.
Impedance-controlled PCBs are also divided into three different situations:
No Impedance Control: This is a situation where you do not need any extra design elements to ensure correct impedance because you have very loose impedance tolerance. Naturally, this will result in a faster-completed, less expensive board because the manufacturer does not have to include any special measures.
Impedance Watching: What is impedance watching? This is a situation where the designer will outline the impedance control trace and the PCB provider adjusts the trace width and dielectric height accordingly. Once the manufacturer approves these specifications, they can begin to manufacture the board. You can request a Time Domain Reflectometry (TDR) test to confirm the impedance for a fee.
Impedance Control: Actual impedance control is something you will typically only request when your design has tight impedance tolerances that could be tough to hit the first time around. When the capability limits of the manufacturer get close to the dimension requirements, it can be tough to ensure target impedance on the initial attempt.
In the case of impedance control, the manufacturer makes the circuit board achieve the target impedance as far as possible. Then they tested TDR to see if they succeeded. If not, they adjust accordingly and try again until they reach the required impedance.
Impedance Control PCB Fabricator
A paper on the non-metallic mineral powder industry jet mill