One. How to make a good PCB board - to clear design goals:
To receive a design task, we must first clear the goal of the design is common PCB board, high-frequency PCB board, small signal processing PCB or both high frequency and small signal processing of printed circuit board (PCB), if it is ordinary PCB board, as long as do layout reasonable and tidy, mechanical accurate dimension no can, such as in load line and long line, it is necessary to use some means to deal with, reducing the load, long-term to strengthen drive, is focused on preventing reflection in the long term. When the board has more than 40MHz signal line, it is to these signal lines for special considerations, such as crosstalk between the lines and so on. If the frequency is higher, the length of wiring is more stringent restrictions, according to the distribution parameters of network theory, high speed circuit connected between the interaction is decisive factor, in the system design can not be ignored. With improvement of the transmission speed of the door, with a corresponding increase in the signal line of the opposition will have to, in proportion to the increase in crosstalk between adjacent signal lines, usually high speed circuit power consumption and heat dissipation is also very big, in high speed PCB should cause enough attention.

When in the millivolt level even microvolt weak signal, the signal line requires special consideration, small signal due to too weak, very easy by other strong signal interference and shielding is often necessary, otherwise it will greatly reduce signal-to-noise ratio. So that the useful signal is overwhelmed by noise, can not be effectively extracted.
Measuring to the board should also be considered in the design stage, the physical location of the test points, test point of isolation and other factors can not be ignored, because some small signal and high frequency signal is not directly to the probe and up were measured.
In addition to consider other related factors, such as the number of boards, the use of components of the package outline, the mechanical strength of the board, etc.. PCB in front of the board, to make the design of the target of the design idea.