Circuit design skills PCB proceso de diseño

El proceso general de diseño básico de PCB es el siguiente: preparación preliminar ->; PCB structure design -& GT; Diseño de PCB – & gt; Cableado – & gt; Optimización de enrutamiento y serigrafía -> Network and DRC inspections and structural inspections – > Plate making.

First: preparation. This includes preparing component libraries and schematics. “To do good work, must first sharpen its device”, to make a good board, in addition to the principle of good design, but also draw well. Before PCB design, the component library of schematic SCH and the component library of PCB should be prepared first. Peotel libraries can be used, but in general it is difficult to find a suitable library, it is best to make your own library according to the standard size information of the selected device. In principle, make PCB component library first, and then SCH component library. Los requisitos de la biblioteca de componentes de PCB son altos, afectan directamente a la instalación de la placa; SCH’s component library requirements are relatively loose, as long as attention is paid to the definition of pin attributes and the corresponding relationship with PCB components. PS: Note the hidden pins in the standard library. Luego está el diseño esquemático, listo para hacer el diseño de PCB.

Segundo: diseño estructural de PCB. En este paso, de acuerdo con el tamaño de la placa de circuito y el posicionamiento mecánico, la superficie de la placa de PCB se dibuja en el entorno de diseño de PCB, y los conectores, botones / interruptores, orificios para tornillos, orificios de montaje, etc. se colocan de acuerdo con los requisitos de posicionamiento. And fully consider and determine the wiring area and non-wiring area (such as how much of the screw hole around the non-wiring area).

Tercero: diseño de PCB. Layout is basically putting devices on a board. At this point, if all the preparatory work mentioned above is done, the network table can be generated on the schematic diagram (Design- >; CreateNetlist) y luego importe la tabla de red en el diagrama de PCB (design-gt; LoadNets). Vea el alboroto del dispositivo de toda la pila, entre los pines y la conexión de la línea de vuelo. A continuación, puede diseñar el dispositivo. The general layout is carried out according to the following principles:

(1). According to the electrical performance reasonable partition, generally divided into: digital circuit area (that is, afraid of interference, and interference), analog circuit area

(fear of interference), power drive area (interference source);

(2). Complete the same function of the circuit, should be placed as close as possible, and adjust the components to ensure the most simple connection; At the same time, adjust the relative position between the functional blocks to make the connection between the functional blocks the most concise;

(3). Installation position and installation intensity should be considered for components with large mass; The heating element should be separated from the temperature sensitive element, and if necessary, thermal convection measures should be considered;

(4). I/O drive device as close as possible to the edge of the printing plate, close to the outlet connector;

(5). Clock generator (such as: crystal oscillator or clock oscillator) should be as close as possible to the device using the clock;

6. In each integrated circuit between the power input pin and the ground, need to add a decoupling capacitor (generally using high frequency good monolithic capacitor); También se puede colocar un condensador de tantalio alrededor de varios circuitos integrados cuando el espacio de la placa de circuito es reducido.

Todos los propietarios. Relay coil to add discharge diode (1N4148 can be);

Hoy. Layout requirements should be balanced, dense and orderly, not top-heavy or heavy

— Special attention should be paid to the actual size (area and height) of the components and the relative position of the components when placing the components to ensure the electrical performance of the circuit board and the feasibility and convenience of production and installation. At the same time, the above principles should be reflected

Under the premise, modify the placement of devices appropriately to make them neat and beautiful. For example, the same devices should be placed neatly and in the same direction, instead of being “strewn at random”. This step concerns the difficulty of board integral figure and next wiring degree, want to spend big effort to consider so. When layout, can make preliminary wiring first to not quite affirmative place, sufficient consideration.

Cuarto: cableado. El cableado es el proceso más importante en el diseño de PCB. This will directly affect the performance of PCB board. In the process of PCB design, wiring generally has such three levels of division: the first is the distribution, which is the most basic requirement of PCB design. If the line is not cloth, get everywhere is flying line, it will be a unqualified board, can say that there is no entry. The second is the satisfaction of electrical performance. Este es el estándar para medir si una placa de circuito impreso está calificada. This is after the distribution, carefully adjust the wiring, so that it can achieve the best electrical performance. Luego está la estética. If your wiring cloth was connected, also do not have the place that what affects electric appliance performance, but look past desultorily, add colourful, brightly colored, that calculates how your electric appliance performance is good, still be rubbish in others eye. This brings great inconvenience to testing and maintenance. El cableado debe ser ordenado y uniforme, no entrecruzado sin reglas. All these should be achieved in the context of ensuring electrical performance and meeting other individual requirements, otherwise it is to abandon the essence. El cableado debe realizarse de acuerdo con los siguientes principios:

(1). En general, el cable de alimentación y el cable de tierra deben enrutarse primero para garantizar el rendimiento eléctrico de la placa de circuito. En el alcance que permite la condición, amplíe el ancho de la fuente de alimentación, el cable de tierra en la medida de lo posible, es mejor que el cable de tierra sea más ancho que la línea de energía, su relación es: cable de tierra> línea de energía> línea de señal, generalmente el ancho de la línea de señal es : 0.2 ~ 0.3 mm, el ancho más delgado puede alcanzar 0.05 ~ 0.07 mm, la línea eléctrica es generalmente de 1.2 ~ 2.5 mm. La PCB de un circuito digital se puede utilizar en un circuito con conductores de tierra anchos, es decir, una red de tierra. (La tierra analógica no se puede utilizar de esta manera).

(2). In advance, wire strict requirements (such as high frequency line) for wiring, input and output side line should avoid adjacent parallel, so as not to produce reflection interference. When necessary, ground wire should be added to isolate, and the wiring of two adjacent layers should be perpendicular to each other, which is easy to produce parasitic coupling in parallel.

(3). The oscillator housing should be grounded, and the clock line should be as short as possible, and not spread all over the place. Below the clock oscillation circuit, the special high-speed logic circuit should increase the area of the ground, and should not go to other signal lines, so that the surrounding electric field tends to zero;

(4). In order to reduce the radiation of high frequency signal, 45O broken line should be used as far as possible, instead of 90O broken line. (High requirements of the line also use double arc)

(5). Any signal line should not form a loop, if unavoidable, loop should be as small as possible; La línea de señal a través del orificio debe ser lo más pequeña posible;

6. The key line should be short and thick, with protection on both sides.

Todos los propietarios. When the sensitive signal and noise field signal are transmitted through flat cable, the method of “ground – signal – ground wire” is used.

Hoy. Test points should be reserved for key signals to facilitate production and maintenance testing

Pet-name ruby. After schematic diagram wiring is completed, wiring should be optimized; At the same time, after the preliminary network check and DRC check is correct, the ground wire is filled in the area without wiring, and a large area of copper layer is used as ground wire, and the unused places are connected with the ground as ground wire on the printed board. Or make it multi-layer board, power supply, grounding line each occupy a layer.

— PCB wiring process requirements

(1). línea

Generally, the signal line width is 0.3mm(12mil), and the power line width is 0.77mm(30mil) or 1.27mm(50mil). Linea con

The distance between lines and between lines and pads should be greater than or equal to 0.33mm(13mil). In practical application, it should be considered to increase the distance when conditions permit; When the cabling density is high, it is advisable (but not recommended) to use two cables between IC pins. The width of the cables is 0.254mm(10mil), and the distance between the cables is not less than 0.254mm(10mil).

Under special circumstances, when the pin of the device is dense and the width is narrow, the line width and line spacing can be appropriately reduced.

(2). PAD (PAD)

The basic requirements of PAD and transition hole (VIA) are: the diameter of PAD is greater than 0.6mm than the diameter of hole; For example, universal pin type resistors, capacitors and integrated circuits, using disk/hole size 1.6mm/0.8mm (63mil/32mil), socket, pin and diode 1N4007, using 1.8mm/1.0mm (71mil/39mil). In practical application, it should be determined according to the size of the actual components. If conditions are available, the size of the pad can be appropriately increased. The installation aperture of the components designed on the PCB board should be about 0.2 ~ 0.4mm larger than the actual size of the pins.

(3). Through hole (VIA)

Generally 1.27mm/0.7mm(50mil/28mil);

When the wiring density is high, the hole size can be appropriately reduced, but not too small, can consider 1.0mm/0.6mm(40mil/24mil).

(4). Spacing requirements for pads, wires and through-holes

PADandVIA: ≥0.3mm (12mil)

PADandPAD: ≥0.3mm (12mil)

PADandTRACK: ≥0.3mm (12mil)

TRACKandTRACK: ≥0.3mm (12mil)

Cuando la densidad es alta:

PADandVIA: ≥0.254mm (10mil)

PADandPAD: ≥0.254mm (10mil)

PADandTRACK: ≥0.254mm (10mil)

TRACKandTRACK: ≥0.254mm (10mil)

Quinto: optimización del cableado y serigrafía. “There is no best, only better”! No importa cuánto esfuerzo ponga en el diseño, cuando haya terminado, mírelo de nuevo y todavía sentirá que puede cambiar mucho. Una regla general de diseño es que el cableado óptimo requiere el doble de tiempo que el cableado inicial. Once you feel that nothing needs fixing, you can Place copper. PolygonPlane). Laying copper generally laying ground wire (pay attention to the separation of analog and digital ground), multilayer board may also need to lay power. For screen printing, we should pay attention to not be blocked by the device or removed by the hole and pad. Al mismo tiempo, el diseño para enfrentar la superficie del componente, la parte inferior de la palabra debe ser un procesamiento de espejo, para no confundir el nivel.

Sexto: verificación de la red y DRC y verificación de la estructura. En primer lugar, partiendo de la premisa de que el diseño esquemático es correcto, los archivos de red de PCB generados y los archivos de red esquemática son NETCHECK para la relación de conexión física, y el diseño se modifica oportunamente de acuerdo con los resultados del archivo de salida para garantizar la corrección de la relación de conexión de cableado; Después de que la verificación de la red se haya pasado correctamente, la verificación DRC se llevará a cabo en el diseño de la PCB y el diseño se modificará de acuerdo con los resultados del archivo de salida a tiempo para garantizar el rendimiento eléctrico del cableado de la PCB. Finalmente, la estructura de instalación mecánica de PCB debe ser revisada y confirmada más a fondo.

Séptimo: fabricación de platos. It is best to have a review process before doing so.

El diseño de PCB es una prueba de la mente del trabajo, que está cerca de la mente, alta experiencia, el diseño de la placa es bueno. Por lo tanto, el diseño debe ser extremadamente cuidadoso, considerar completamente los factores de todos los aspectos (como facilitar el mantenimiento y la inspección de esto que mucha gente no considera), la excelencia, será capaz de diseñar una buena placa.