In any power supply design , PCB board are the last link in the physical design , the design method determines the electromagnetic interference and power stability , we have to analyze these specific areas:
First, the establishment of component parameters from the schematic to the PCB design process - " input netlist principle - " Design parameters - " manual layout - " hand- wiring - " validate design - " Review - "CAM output.
Second, the parameters must be able to meet the conductor spacing of adjacent electrical safety requirements , and in order to facilitate the operation and production , the spacing should be as wide as some . Minimum distance at least be able to fit withstand voltage wiring density at lower pitch signal lines can be appropriately increased to high and low disparity signal lines should be as short as possible and increase the spacing, under normal circumstances will take the line spacing set 8mil..
The inner side of the hole edge of the pad of the printed circuit board is greater than the distance to 1mm, to avoid defects in the processing of lead pads . When traces connected with smaller pads , pads and traces the connection between To design a teardrop-shaped , so that the benefits are not easy to paddle from the skin , but the traces and pads easily disconnected.
Third, the components layout proved , even if the circuit schematic design properly , improperly printed circuit board design , will also have an adverse impact on the reliability of electronic equipment. For example , if the PCB two thin parallel lines are very close to the delay of the signal waveform is formed in the transmission line terminals form reflected noise ; interference due to power , ground and thoughtful consideration is not caused , the product will performance degradation , therefore , in the design of printed circuit boards , they should pay attention to using the right approach.
Fourth, the switching power supply wiring includes a high-frequency signal , and any traces on the PCB can serve as an antenna , the length and width of the printed lines will affect the resistance and inductance, thus affecting the frequency response. Even traces also coupled through the DC signal from the adjacent tracks to radio signals and cause electrical problems ( or even re- radiated interference signals ) .
Fifth, after checking the wiring design is complete, check the wiring needs to be carefully designed to comply with applicable rules established by the designer , but also need to confirm the rules established by the PCB production process meets the needs of the general inspection line and lines, weld lines and components from the plate , line and through holes , pads and through-hole components , through-hole and through hole between reasonable, whether to meet production requirements. Power line and ground width is appropriate, whether there can make the PCB ground widened place. Note: Some errors can be ignored, for example, that some part of the Outline of the connector on the frame , the error when checking the pitch ; addition each modified after traces and vias , we must re- clad once.
Sixth, the review under "PCB Checklist" , including design rules, traces rationality , power , ground network layer definition, line width, spacing, pads , vias settings, but also focus on the review device layout , high-speed traces clock network and shielding, decoupling capacitor placement and connections .
