PCB board layout techniques--PCB Assembly
When is the choice to do double-sided PCB or multilayer, the maximum operating frequency and PCB Assembly depends on the complexity of the system and the requirements of the assembly to determine the density. When the clock frequency than the best selection of MLB 200MHZ. If the operating frequency over 350MHz, the best choice to PTFE as the dielectric layer printed circuit board, because of its high-frequency attenuation to be smaller, the parasitic capacitance to be smaller, the transmission speed to be faster, but also because more Z0 large provincial power, on the china PCB Assembly traces have the following principle requires
(1) between all the parallel signal lines leave large intervals to try to reduce crosstalk. If there are two signal lines are in close proximity, it is best to go between the two lines of a ground wire, so you can play a role in shielding.
(2), signal transmission lines designed to avoid sharp turn, and to prevent the transmission line characteristic impedance of the mutations have a reflection, to try to design into a certain size of the uniform circular line.
The width of the PCB Assembly according to the microstrip line and strip line characteristic impedance calculation formula, the printed circuit board microstrip line characteristic impedance is generally between 50 ~ 120Ω. To get a large characteristic impedance, line width must be very narrow. But it is not easy to make fine lines. Various factors to consider, the general choice 68Ω impedance value of about more appropriate, because the choice of 68Ω characteristic impedance, delay time and can achieve the best balance between power consumption.