Contents of technical specifications classified by parts1 PCB wiring and layout PCB wiring and layout isolation criteria: strong and weak current isolation, large and small voltage isolation, high and low frequency isolation, input and output isolation, digital analog isolation, input and output isolation, the demarcation standard is an order of magnitude. Isolation methods include: space away from ground wire separation.2pcb wiring and layout crystal oscillator should be close to IC as far as possible, and the wiring should be thick3pcb wiring and layout crystal shell groundingWhen 4pcb wiring and layout clock wiring are output through the connector, the pins on the connector should be covered with grounding pins around the clock line pins5pcb wiring and layout let analog and digital circuits have their own power and ground paths respectively. If possible, the power and ground paths of these two parts of circuits should be widened or separate power layer and ground layer should be adopted, so as to reduce the impedance of power and ground circuits and reduce any possible interference voltage in power and ground circuits6pcb wiring and layout the analog ground and digital ground of PCB working separately can be connected at a single point near the system ground point. If the power supply voltage is consistent, the power supply of analog circuit and digital circuit can be connected at a single point at the power supply inlet. If the power supply voltage is inconsistent, a 1 ~ 2NF capacitor is connected near the two power supplies to provide a path for the signal return current between the two power supplies7pcb wiring and layout if the PCB is inserted on the motherboard, the power supply and ground of analog and digital circuits of the motherboard should also be separated. The analog ground and digital ground should be grounded at the grounding point of the motherboard, and the power supply should be connected at a single point near the system grounding point. If the power supply voltage is consistent, the power supply of analog and digital circuits should be connected at a single point at the power inlet. If the power supply voltage is inconsistent, the power supply should be connected at a single point near the two power supplies The capacitance of 1 ~ 2NF provides a path for the signal return current between the two power supplies8 PCB wiring and layout when high speed, medium speed and low speed digital circuits are mixed, different layout areas should be assigned to them on the printed circuit boardThe wiring and layout of 9pcb should be separated from low-level analog circuit and digital logic circuit as much as possible10 PCB wiring and layout in the design of multilayer printed circuit board, the power plane should be close to the ground plane, and arranged under the ground plane.11pcb wiring and layout in the design of Multilayer PCB, the wiring layer should be arranged adjacent to the whole metal planeIn the design of multi-layer printed circuit board, the digital circuit and analog circuit are separated. If possible, the digital circuit and analog circuit are arranged in different layers. If it must be arranged on the same floor, it can be remedied by trenching, adding grounding lines and separating. Analog and digital ground and power supply should be separated, not mixedThe clock circuit and high frequency circuit are the main interference and radiation source, so it must be arranged separately and far away from the sensitive circuitPay attention to the waveform distortion in the process of long line transmission in 14pcb wiring and layout The best way to reduce the loop area of interference source and sensitive circuit is to use twisted pair and shielded wire to make the signal wire and ground wire (or current carrying circuit) twisted together, so as to make the distance between signal and ground wire (or current carrying circuit) closest16pcb wiring and layout increase the distance between the lines, so that the mutual inductance between the interference source and the induced line is as small as possibleIf possible, the circuit of the interference source and the induced circuit are arranged at right angles (or close to right angles), which can greatly reduce the coupling between the two circuitsThe best way to reduce the capacitance coupling is to increase the distance between 18 PCB wiring and layoutBefore the formal wiring, the first thing is to classify the circuit. The main classification method is based on power level, which is divided into several groups every 30dB power levelThe wires with different types of 20pcb wiring and layout shall be bundled and laid separately. The adjacent wires can also be grouped together after shielding or twisting. The minimum distance between the wiring harness of classified laying is 50 ~ 75mm21PCB The gain control resistance and bias resistance (up-down) of the amplifier, up-down and voltage stabilized rectifier circuit should be close to the amplifier, active device, its power supply and ground as far as possible to reduce the decoupling effect (improve the transient response time).22pcb wiring and layout the bypass capacitor is placed close to the power inputThe 23 PCB wiring and layout decoupling capacitor is placed at the power input. As close to each IC as possiblePCB routing and layout pcb basic characteristic impedance: determined by the quality of copper and cross section area. Specific: 1 oz 0.49 MOH / unit areaCapacitance: C = eoera / h, EO: free space permittivity, Er: PCB substrate permittivity, a: current range, H: wire spacingInductance: average distribution in the wiring, about 1NH / mFor ounces of copper wire, under 0.25 mm (10 mil) thick FR4 rolling, the 0.5 mm wide and 20 mm long wire above the ground layer can produce 9.8 milliohm impedance, 20 NH inductance and 1.66 pf coupling capacitance with the ground.25pcb wiring and layout the basic principles of PCB wiring are as follows: increasing the line spacing to reduce the crosstalk of capacitance coupling; parallel laying of power lines and ground wires to optimize the PCB capacitance; laying sensitive high-frequency lines away from high noise power lines; widening the power lines and ground wires to reduce the impedance of power lines and ground wires; setting the sensitive high-frequency lines in a position far away from high noise power lines;26pcb wiring and layout segmentation: physical segmentation is used to reduce the coupling between different types of signal lines, especially the power supply and ground wire27pcb wiring and layout local decoupling: for the decoupling of local power supply and IC, a large capacity bypass capacitor is used between the power input port and PCB for low-frequency pulse filtering and meeting the requirements of burst power. Decoupling capacitors are used between the power supply and ground of each IC, and these decoupling capacitors should be as close to the pins as possible.Separation of PCB routing and layout routing: minimize crosstalk and noise coupling between adjacent lines in the same layer of PCB. 3W specification is used to process the key signal path.29pcb wiring and layout protection and shunt circuit: adopt two sides of ground wire protection measures for key signals, and ensure that both ends of the protection circuit are grounded30pcb wiring and layout single layer PCB: the ground wire shall be kept at least 1.5mm wide, and the change of jumper and ground wire width shall be kept to the minimum31pcb wiring and layout double layer PCB: the ground grid / lattice wiring is preferred, and the width is kept above 1.5mm. Or put the ground on one side and the signal power on the other32pcb wiring and layout protection ring: use the ground wire to form a ring to isolate the protection logic33pcb wiring and layout pcb capacitance: PCB capacitance is produced on the multilayer board due to the thin insulation layer of power supply surface and ground. It has the advantages of very high frequency response and low series inductance uniformly distributed on the whole plane or line. It is equivalent to a decoupling capacitor evenly distributed on the whole board.34pcb wiring and layout high speed circuit and low speed circuit: high speed circuit should be close to the ground, low speed circuit should be close to the power supply.Copper filling of ground: copper filling must ensure grounding.The routing direction of 35pcb is orthogonal to the routing direction of adjacent layers, so as to avoid different signal lines in the same direction in the adjacent layers, so as to reduce unnecessary inter layer interference. When it is difficult to avoid this situation due to the board structure limitation (such as some backplanes), especially when the signal rate is high, the ground plane should be considered to isolate each routing layer, and the ground signal line should be considered to isolate each signal line;In order to avoid "antenna effect", the floating wiring at one end is not allowed in the wiring and layout of 36pcb.37pcb wiring and layout impedance matching inspection rules: the wiring width of the same grid should be consistent, the change of line width will cause uneven line characteristic impedance, and reflection will occur when the transmission speed is high, which should be avoided in the design. Under some conditions, the change of line width may not be avoided, so the effective length of the inconsistent part in the middle should be minimized.38pcb wiring and layout prevent signal lines from forming self loop between different layers, which will cause radiation interference.39pcb wiring and layout short line rule: wiring as short as possible, especially important signal lines, such as clock line, be sure to put its oscillator close to the device.40 PCB wiring and layout chamfering rules: PCB design should avoid acute angle and right angle, produce unnecessary radiation, at the same time process performance is not good, all line to line angle should be greater than 135 degrees41pcb wiring and layout: the line from filter capacitor pad to connection pad shall be connected with 0.3mm thick line, and the interconnection length shall be ≤ 1.27mm.42pcb wiring and layout in general, the high frequency part is set in the interface part to reduce the wiring length. At the same time, we should also consider the segmentation of high / low frequency part of the ground plane, which is usually divided into two parts, and then connected by a single point at the interface.43pcb wiring and layout for the area with dense through holes, we should pay attention to avoid the interconnection between the power supply and the hollowed out area of the stratum, forming the division of the plane layer, thus damaging the integrity of the plane layer, and further leading to the increase of the loop area of the signal line in the stratum.44pcb wiring and layout power layer projection non overlapping criteria: PCB board with more than two layers (including) and different power layers should avoid overlapping in space, mainly to reduce the interference between different power sources, especially between some power sources with large voltage difference, the problem of power plane overlapping must be avoided, if it is difficult to avoid, the middle insulating layer can be considered.45pcb wiring and layout 3W rule: in order to reduce line to line interference, the line spacing should be large enough. When the line center distance is not less than 3 times the line width, 70% of the electric field can not interfere with each other. If 98% of the electric field can not interfere with each other, 10W rule can be used.More details will follow
7S production management
Sorting: increase the operation area; smooth logistics, prevent misuse, etc.Rectification: the workplace is clean and clear, clear at a glance, reduce the time of taking and putting things, improve work efficiency, and maintain orderly work order.Cleaning: remove the dirt in the site and the materials and garbage in the operation area.Cleaning: to make the arrangement, rectification and cleaning work become a routine and system, which is the basis of standardization and the beginning of an enterprise's formation of corporate culture.Literacy: through literacy, employees can become a person who abides by rules and regulations and has a good work literacy habitSafety: ensure the personal safety of employees, ensure the continuous safety and normal production, and reduce the economic losses caused by safety accidents.Saving: it is to make rational use of time, space, energy and other aspects, so as to give full play to their maximum efficiency, so as to create a highly efficient workplace with the best use of materialsdefinition7S (sorting, rectifying, sweeping, cleaning, quality, safety and saving) management mode ensures the elegant production and office environment, good work order and strict work discipline of the company. At the same time, it is also the basic requirement to improve work efficiency, produce high-quality and precision products, reduce waste, save material cost and time cost.management systemThe so-called 7S are Seiri, Seiton, Seiso, seikeetsu, Shitsuke, safety and saving