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How is pyrolysis technology applied in circuit boards As an efficient means of waste treatment and recycling, pyrolysis technology can play an important role in the recycling of waste circuit boards. With the further research on the basic theory of pyrolysis technology and the development of pyrolysis equipment, it will become one of the most important methods for recycling circuit boards in waste electrical and electronic equipment in the future. Although the measurement of bromine-containing products in the pyrolysis of circuit boards is limited to qualitative analysis or based on the analysis of the total amount of bromine elements, precise quantitative analysis and detection of specific bromine-containing substances cannot be achieved, so it cannot provide enough complete information to determine the transformation and migration rules of bromine-containing flame retardants in the pyrolysis process. However, many researchers have carried out some attempts to remove brominated p
The method of rational layout of components in PCB design First, beauty should not only consider the orderly placement of components, but also consider the beautiful flow of the line. Because the general layman sometimes more emphasis on the former, in order to one-sided evaluation of the advantages and disadvantages of circuit design, in order to the image of the product, the former should be given priority when the performance requirements are not harsh. However, in high-performance occasions, if you have to use dual panels, but also packaged in the inside, usually can not see, you should prioritize the beauty of the line. Second, the force circuit board should be able to withstand various external forces and vibrations during installation and work. Therefore, the circuit board should have a reasonable shape, and the positions of various holes (screw holes, special-shaped holes) on the board should be reasonably arranged. Generally, the distance between the hole and the edge of
Electromagnetic compatibility design in PCB circuits Once electrostatic discharge occurs, it should be bypassed as soon as possible, and do not directly invade the internal circuit. For example, if the internal circuit is shielded by a metal chassis, the chassis should be well grounded, and the grounding resistance should be as small as possible, so that the discharge current can flow into the ground from the outer chassis, and the disturbance caused by the discharge of surrounding objects can also be imported into the ground, without affecting the internal circuit. For a metal chassis, the circuits in the chassis are grounded through I/O cables and power cables. When electrostatic discharge occurs on the chassis, the potential of the chassis increases, but the potential of the internal circuits is kept near the ground potential due to grounding. At this time, there is a large potential difference between the chassis and the circuit. This causes a secondary arc between the chassis a
PCB Cable design A properly designed cable protection system may be the key to improving the system's ESD non-susceptibility. As the largest "antenna" in most systems - I/O cables are particularly susceptible to ESD interference that induces large voltages or currents. On the other hand, the cable also provides a low impedance channel to ESD interference if the cable shield is connected to the housing. Through this channel, ESD interference energy can be released from the system grounding loop, thus avoiding conductive coupling indirectly. In order to reduce ESD interference radiation coupling to the cable, the line length and loop area should be reduced, common mode coupling should be suppressed and metal shielding should be used. For input/output cables, shielding cables, common mode chokes, overvoltage clamp circuits, and cable bypass filters can be used. At both ends of the cable, the cable shield must be connected to the housing shield. Installing a common mode choke on the int
PCB copper-platinum treatment Because the current IC working clock (digital IC) is getting higher and higher, its signal for the width of the line put forward certain requirements, the line width (copper platinum) is good for low frequency strong current, but for high frequency signal and data line signal, it is not the case, the data signal is more synchronization, high frequency signal is affected by skin effect. Therefore, the high-frequency signal should be thin and not wide, and should be short and not long, which involves the layout problem (the coupling of signals between devices), which can reduce the induced electromagnetic interference. The data signal, however, appears on the circuit in the form of pulse, and its higher harmonic content is the decisive factor to ensure the correctness of the signal. The same wide copper platinum will have a skin effect on high speed data signals (distributed capacitance/inductance increases), which will lead to signal deterioration, data
PCB layout/wiring, impact on electrical performance Digital ground cables should be separated from analog ground cables. This has a certain degree of difficulty in practice. To develop a better board, you first have to understand the electrical aspects of the IC you are using, which pins will produce high order harmonics (digital signals or the rise/fall edge of the switching square wave signal), which pins are susceptible to electromagnetic interference, the signal block diagram (signal processing unit block diagram) inside the IC helps us understand. The layout of the whole machine is the first condition to determine the electrical performance, and the layout of the board is more to consider the direction or process of the signal/data between the IC, the big principle is easy to produce electromagnetic radiation as close to the power part as possible; The weak signal processing part is mostly determined by the overall structure of the equipment (that is, the overall planning of t
Some feasible processes for PCB production First, the line 1. Minimum line width: 6mil (0.153mm). That is to say, if the line width is less than 6mil, it will not be produced, (the minimum line width distance of the inner layer of the multi-layer board is 8MIL) If the design conditions permit, the larger the design, the better the line width, the better the factory production, the higher the yield, the general design routine is about 10mil, this point is very important, the design must be considered. 2. Minimum line distance: 6mil (0.153mm).. The minimum line distance, that is, the line to the line, the distance from the line to the pad is not less than 6mil from the production point of view, the bigger the better, the general practice in 10mil, of course, the design conditions, the bigger the better this point is very important, the design must be considered. 3.Line to contour line spacing 0.508mm(20mil) Two, via holes (commonly known as conductive holes) 1. Minimum aperture :
The main factors to be considered in the mechanical design of printed circuit boards 1) The best panel size suitable for printed circuit board production; 2) Location of panel mounting holes, brackets, splints, clamps, shielding boxes and radiators; 3) Suitable fixed devices for heavier components; 4) Suitable aperture for component installation; 5) The assembled circuit board should have pressure resistance and shock resistance during transportation; 6) The assembly method of the circuit board (vertical installation/horizontal installation); 7) Cooling method; 8) Special placement requirements for components, similar to those operating on the front panel, such as buttons, rheostat, etc. Steps of PCB layout design Before the layout design begins, a complete and detailed description of the circuit is needed, mainly including the following aspects: 1) Schematic diagram, including details of components, connections and specifications of edge connectors. 2) Component list, in
The aperture of pad in circuit board manufacturing design is discussed Test pads must be provided for all nodes in accordance with ANSI/IPC 2221 requirements. A node is an electrical connection point between two or more components. A test pad requires a signal name (node signal name), an x-y axis related to the reference point of the printed circuit board, and the coordinate position of the test pad (indicating which side of the printed circuit board the test pad is located on). Mounting information is required for the SMT, and thermobonding technology for the PCB assembly layout is also required to promote testability in the circuit with the help of "in-circuit test fixtures" or what is commonly referred to as "nail bed fixtures". To achieve this, it is necessary to: 1) The diameter of the test pad specially used for detection should not be less than 0.9mm. 2) The space around the test pad should be greater than 0.6mm and less than 5mm. If the height of the component is greater t
Circuit board plate grade and grade introduction According to the grade level from bottom to high divided as follows: 94HB/94VO/22F/CEM-1/CEM-3/FR-4 The details are as follows: 94HB: ordinary cardboard, not fireproof (lowest grade material, die punching, can not be used as a power board) 94V0: Flame retardant board (die punching) 22F: Single side half glass fiber board (die punching) Cim-1: Single glass fiber board (must be computer drilling, can not die punching) Cim-3: double-sided half-glass fiber board (in addition to double-sided cardboard is the lowest end of the double-panel material, simple double-panel can be used with this material, than FR-4 will be cheaper 5~10 yuan/square meter) FR-4: double-sided fiberglass board
Introduction to aluminum substrate First, the characteristics of LED aluminum substrate 1. Use external mount technology (SMT); 2. Extremely useful treatment of thermal diffusion in circuit design schemes; 3. Reduce the operating temperature of the commodity, improve the power density and reliability of the commodity, and extend the service life of the commodity; 4. Reduce the volume of goods, reduce the hardware and installation costs; 5. Replace the fragile ceramic substrate to achieve very good mechanical durability. Second, the layout structure of LED aluminum substrate Aluminum clad copper plate is a metal circuit board data, composed of copper foil, thermal insulation layer and metal substrate, its layout is divided into three layers: Line layer: equivalent to the copper clad plate of the usual PCB, line copper foil thickness loz to 10oz. Insulation layer: Insulation layer is a layer of low thermal resistance thermal insulation material. BaseLayer substrate: A metal
According to the grade level from bottom to high divided as follows: 94HB/94VO/22F/CEM-1/CEM-3/FR-4 The details are as follows: 94HB: ordinary cardboard, not fireproof (lowest grade material, die punching, can not be used as a power board) 94V0: Flame retardant board (die punching) 22F: Single side half glass fiber board (die punching) Cim-1: Single glass fiber board (must be computer drilling, can not die punching) Cim-3: double-sided half-glass fiber board (in addition to double-sided cardboard is the lowest end of the double-panel material, simple double-panel can be used with this material, than FR-4 will be cheaper 5~10 yuan/square meter) FR-4: double-sided fiberglass board
Introduction to aluminum substrate First, the characteristics of LED aluminum substrate 1. Use external mount technology (SMT); 2. Extremely useful treatment of thermal diffusion in circuit design schemes; 3. Reduce the operating temperature of the commodity, improve the power density and reliability of the commodity, and extend the service life of the commodity; 4. Reduce the volume of goods, reduce the hardware and installation costs; 5. Replace the fragile ceramic substrate to achieve very good mechanical durability. Second, the layout structure of LED aluminum substrate Aluminum clad copper plate is a metal circuit board data, composed of copper foil, thermal insulation layer and metal substrate, its layout is divided into three layers: Line layer: equivalent to the copper clad plate of the usual PCB, line copper foil thickness loz to 10oz. Insulation layer: Insulation layer is a layer of low thermal resistance thermal insulation material. BaseLayer substrate: A metal
Single panel features The single panel is on the most basic PCB, the parts are concentrated on one side, and the wires are concentrated on the other side. Because the wire only appears on one side, we call this PCB Single-sided. Because a single panel has many strict restrictions on the design circuit (because there is only one side, the wiring can not cross and must go around a separate path), only early circuits used such boards; The wiring diagram of the single panel is mainly Screen Printing, that is, the resistance is printed on the copper surface, and then the welding resistance is etched to prevent the mark, and finally the pilot hole and the shape of the part are completed by punching. In addition, some of the products produced in small quantities and in a variety of ways, the photographic method of pattern formation with photoresist is used.
Double-sided circuit board Double-Sided Boards have wiring on both sides. However, in order to use the wires on both sides, there must be a proper circuit connection between the two sides. This "bridge" between circuits is called a pilot hole (via). A pilot hole is a small hole filled with or coated with metal on the PCB, which can be connected with wires on both sides. Because the area of the dual panel is twice as large as that of the single panel, and because the wiring can be interlaced (can be wound around the other side), it is more suitable for use in more complex circuits than the single panel. Strictly speaking, double panel is a very important PCB board in the circuit board, its use is very simple to see whether a PCB board is double panel, I believe that friends' understanding of the single panel is completely able to grasp, double panel is an extension of the single panel, meaning that the single panel line is not enough to turn to the opposite, Another important featur
Due to the increase in the package density of integrated circuits, the interconnection is highly concentrated, which makes the use of multi-substrate necessary. In the layout of printed circuits, unforeseen design problems arise, such as noise, stray capacitance, crosstalk, etc. Therefore, the printed circuit board design must be committed to minimizing the length of the signal line and avoiding parallel routes. Obviously, in a single panel, or even a dual panel, none of these needs can be satisfactorily answered due to the limited number of intersections that can be achieved. In the case of a large number of interconnect and cross requirements, the board must be expanded to more than two layers in order to achieve a satisfactory performance, thus the emergence of multi-layer circuit boards. Therefore, the original intention of manufacturing multilayer circuit boards is to provide more freedom to choose the appropriate routing path for complex and/or noise-sensitive electronic ci
Flexible circuit board definition is also called flexible printed circuit board, or soft printed circuit board. According to IPC's definition, flexible printed circuit board is a product that is designed and made of circuit graphics on a flexible substrate in a printed manner. Flexible circuit board advantages Flexible printed circuit board is an important type of PCB. Its characteristics are: (1) FPC has small size and light weight. (2) FPC can move, bend and twist. (3) FPC has excellent electrical properties, dielectric properties and heat resistance. (4) FPC has high assembly reliability and assembly operability. (5) The FPC can be installed with a three-position connection. (6) FPC is beneficial to thermal diffusion. (7) Low cost. (8) Continuity of processing. Cause of silver layer of circuit board By analyzing the root cause of the defects, these defect rates can be minimized through a combination of process improvement and parameter optimization. The Giavani effec
PCB wave soldering In order to ensure that the surface of the board and the surface of the lead are quickly and completely soaked by solder, the flux must be coated. Generally, rose-scented flux or water-soluble flux with a relative density of 0.81 ~ 0.87 is used. ② The PCB circuit board coated with flux should be preheated, which should generally be controlled at 90 ~ 110℃. A good grasp of the preheating temperature can reduce or avoid the occurrence of pointed and round solder joints. ③ In the welding process, the solder temperature should generally be controlled within the range of 250 ° C ±5 ° C, and whether the temperature is suitable for directly affecting the welding quality; The Angle of inclination of the welding fixture into the crest should be adjusted to 6. Around; The welding speed should be mastered at 1 ~ 1.6n/min; Solder groove tin surface crest height is about lOmm, the peak is generally controlled in the board thickness of 1/2 ~ 213, too large will lead to molten
PCB manual welding ① Check the insulation materials in advance before welding, and there should be no burns, scorches, deformation, cracks and other phenomena, and do not allow burns or damage to components during welding. The welding temperature should usually be controlled at about 260 ° C, not too high or too low, otherwise it will affect the welding quality. ③ The welding time is usually controlled within 3s. For welding parts with large heat capacity such as multi-layer plates, the entire welding process can be controlled within 5s; For the welds of integrated circuits and thermal components, the entire process should not exceed 2s. If it is not welded well within the specified time, it should be re-welded after the welding joint has cooled, and the quality standard of re-welding should be the same as that of the welding joint during a single welding. Obviously, due to the differences in the power of the soldering iron, the heat capacity of the solder joint and other factors,
Component layout principles in PCB design 1) General principle: If the circuit system has both digital circuits and analog circuits. As well as the high-current circuit, it must be arranged separately, so that the coupling between the systems reaches the minimum in the same type of circuit, according to the signal flow and function, the block, the partition of the components. 2) Input signal processing unit, output signal driver should be close to the board side, so that the input and output signal line as short as possible to reduce input and output interference. 3) Component placement direction: components can only be arranged in two directions: horizontal and vertical. Otherwise it is not good for the plug-in. 4) Component spacing. For medium density boards, small components such as low-power resistors, capacitors, Diodes, such as discrete components of each other and plug-in, welding process related, peak welding, component spacing can take 50-100MIL(1.27--2.54MM) manual can
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