In PCB design, layout is an important step to complete product design , it can be said in front of the preparations for it are doing throughout the PCB , layout design process to define the highest and most detailed tips , maximum workload . There are single-sided PCB layout wiring , double-sided and multilayer wiring wiring . Wiring there are two ways : automatic routing and interactive routing , automatic routing before , you can use the interactive advance more stringent requirements for wiring the input and output terminals of adjacent parallel edges should be avoided to avoid reflection interference. Necessary, add ground isolation , wiring two adjacent layers perpendicular to each other and parallel prone to parasitic coupling.
Routability automatic routing , dependent on good placement, routing rules can be pre-set , including bending frequency alignment , the number of vias , step number and so on. Usually the first to explore the type of cloth warp quickly to short-term connectivity , and then wiring labyrinth , first connect to the cloth wiring path for global optimization , it can disconnect the line has cloth as needed . And try to re- wiring to improve the overall effect .
The current high-density PCB design has been felt through-holes are not accustomed to , and it wastes a lot of valuable routing channels to solve this conflict , there has been blind and buried vias technology, which not only completed the role of vias many , but also save a wiring channel the wiring process is completed a more convenient, more smooth, more perfect , PCB board design process is a complex and simple process , in order to have a good grasp it , the majority of electronic engineering design needs personnel to their own experience, to get the true meaning .
Power supply , ground handling
Even the wiring throughout the completion of the PCB was very good, but the interference due to the power supply, ground caused by thoughtless , product performance will decrease , and sometimes even affect the success rate of the product. So for electrical , ground wiring to be taken seriously , the noise power generated by the ground to a minimum to ensure the quality of the product.
For each engaged in electronic product design engineering personnel who are aware of the reasons for the noise between the ground and power lines generated , is only made to reduce noise suppression formula to express :
( 1 ) , is known to add between power and ground decoupling capacitors .
( 2 ) , try to widen the power , ground width , it is better than the power ground wire width, their relationship is : Ground > Power cable> signal line , usually the signal line width : 0.2 ~ 0.3mm, the most by thin width of up to 0.05 ~ 0.07mm, the power line is 1.2 ~ 2.5 mm
Available on a wide PCB ground wire digital circuits to form a loop , constitutes a ground network to use ( analog circuits to not so used)
( 3 ) , a large area with a copper layer is used as a ground on the PCB is not the place to spend all connected with the land use as a ground . Or made of plywood , power , occupied the ground floor of each