General PCB&PCBA basic design process is as follows: preliminary preparation -PCB structure design -PCB layout - wiring - wiring optimization and screen printing - network and DRC inspection and structure inspection - platemaking. Before we make pcb prototype, we will do design a pcb file, so how should we do? Here I will introduce in details:
First: preparation. This includes preparing the component library and schematics. "If you want to do well in your work, you must make good use of your tools. Before PCB design, prepare the component library of schematic diagram SCH and PCB. The component library can use peotel's own library, but in general it is difficult to find the appropriate one. It is better to make the component library by yourself according to the standard size data of the selected device. In principle, first make the PCB component library, then make the SCH component library. PCB has a higher requirement of component library, which directly affects the installation of board. SCH's component library needs to be relatively loose, as long as the pin attributes and corresponding relations with PCB components are well defined. PS: note the hidden pins in the standard library. After that, the design of the schematic diagram is ready to start the PCB design.
Second: PCB structure design. In this step, according to the determined circuit board size and various mechanical positioning, the PCB board surface is drawn under the PCB design environment, and the required connectors, buttons/switches, screw holes, assembly holes and so on are placed according to the positioning requirements. And fully consider and determine the wiring area and the non-wiring area (such as the area around the screw hole belongs to the non-wiring area).
Third: PCB layout. The layout is essentially putting devices on the board. At this point, if all the preparations mentioned above are done, the network table can be generated on the schematic diagram, and then the network table (design-& gt) can be imported on the PCB diagram. LoadNets). You can see that all the devices are going up, and there are flying wire between the pins. Then you can layout the device. The general layout is based on the following principles:According to reasonable electrical performance, it is generally divided into: digital circuit area (i.e. fear of interference and interference), analog circuit area (fear of interference) and power drive area (interference source).
A circuit that performs the same function should be placed as close as possible and the components are adjusted to make the connection as simple as possible. At the same time, adjust the relative position between functional blocks to make the connection between functional blocks the most concise
Installation location and installation strength should be considered for high quality components. The heating element should be placed separately from the temperature sensitive element. However, the I/O drive device is as close to the edge of the printing plate as possible, and is close to the outlet connector;
Clock generators (e.g., crystal or clock oscillations) should be as close as possible to the device that USES the clock.However, a decoupling capacitance (usually single stone capacitance with high frequency) should be added between the power input pin and the ground of each integrated circuit. When the circuit board space is relatively dense, a tantalum capacitor can be added around several integrated circuits.
Charge diode (1N4148) should be added at the coil of relay. The layout should be balanced, well - organized and not heavy or heavy.
Need to pay special attention to: when placed component, must want to consider the actual size of components (in the area and height) and the relative position between the components, to ensure the feasibility of the electrical properties and production of circuit boards installed and convenience at the same time, should be on the premise of guarantee the above principle to reflect, appropriate change device, make it tidy and beautiful, such as the same devices to be neat, in the same direction, can't put strewn at random have send. This step is related to the overall image of the board and the next level of wiring is difficult, so it takes a lot of effort to consider. When layout, not quite sure place can make preliminary wiring first, consider adequately.
Fourth: wiring. Wiring is the most important process in PCB design. This will directly affect the performance of the PCB board. In the design process of PCB, the wiring is generally divided into three levels: first, the layout, then the most basic requirements of PCB design. If all the lines are not connected, you will find a flight line everywhere, which will be a disqualified board, so to speak, not yet. Next is the satisfaction of electrical performance. This is the measure of a printed circuit board. This is after the layout, careful adjustment of the wiring, so that it can achieve the best electrical performance. And then aesthetics. If your wiring cloth is connected, also did not have what to affect the place of electrical performance, but see past desultorily, add colorful, colorful green, that calculate your electrical performance how good, still be rubbish in other people eye piece. This brings great inconvenience to testing and maintenance. The wiring should be uniform and not crisscrossed without any rules. All of these should be realized under the condition of ensuring electrical performance and meeting other individual requirements, otherwise, it is a waste of time.