/Problems to pay attention to when designing printed circuit boards
① Standard components should pay attention to the dimensional tolerances of components from different manufacturers. Non-standard components must be designed in accordance with the actual size of the components and the land pattern and the space between the land.
② When designing high-reliability circuits, the pads should be widened (pad width = 1.1 to 1.2 times of the component solder end width)
③ When the density is high, the pad size of the component library in the CAD software should be corrected.
④ The distance between components, wires, test points, through holes, connection between pads and wires, soldering resistance, etc. must be designed in accordance with standards.
⑤ The repairability should be taken into consideration, such as large size SMD around to leave the size of repair tools to operate
⑥ The problems of heat dissipation, high frequency, and anti-electromagnetic interference should be considered.
⑦The placement position and direction of components should also be designed according to different processes.
⑧PCB design also needs to consider equipment. Different placement machines have different mechanical structures, alignment methods, and PCB transmission methods.Therefore, the positioning hole position of the PCB, the pattern and position of the reference mark (Mark), the shape of the PCB edge, and the position where components cannot be placed near the PCB edge all have different requirements. These are the contents of productive design.
⑨ Consider the corresponding design documents. Because the SMT production line’s dispensing (solder paste) machine, placement machine, online test, x-ray test, AOI automatic optical inspection and other equipment are computer-controlled automated equipment, these devices require programmers to spend considerable time before assembling PCBs Prepare and program. Therefore, the PCB design stage is required to consider production. Once the design is completed, the relevant data files generated by the design are handed over to the SMT production equipment, which can be directly called during programming or related post-processing can drive the processing equipment.
⑩On the premise of ensuring reliability, we must also consider reducing the cost of pcb production.
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