1, layout / wiring, the impact on electrical performance
Digital ground and analog ground to be separated. This has a certain degree of difficulty in the actual operation. To lay out the better board, first of all you have to understand the electrical aspects of your use of IC, which pins will produce high harmonics (digital signal or digital cross-wave signal on the rise / fall), which cited The foot sensor is sensitive to electromagnetic interference, IC internal signal block diagram (signal processing unit block diagram) to help us understand.
Machine layout is to determine the electrical performance of the primary conditions, and the board layout between the more consideration is the IC signal / data from the direction or process, the principle is easy to produce electromagnetic radiation as close to the power part; weak signal processing (As well as the overall design of the equipment), as close as possible to the input or detection head of the signal (probe), which can better improve the signal-to-noise ratio for subsequent signal processing and data identification. More pure signal / accurate data.
2, PCB copper platinum treatment
As the current IC working clock (digital IC) is getting higher and higher, the signal for the width of the line made a certain request, traverse wide (copper platinum) for low frequency current is good, but for high frequency signals and data Line signal, but not the case, the data signal is more emphasis on synchronization, high-frequency signal is more affected by the skin effect, so the high-frequency signal alignment should not be wide, should be short not long, which also involves the layout problem (The coupling between the devices), which can reduce the induced electromagnetic interference.
And the data signal, but it is in the form of pulse on the circuit, the high harmonic component is to ensure the correctness of the signal to play a decisive factor; the same wide copper platinum will high-rate data signal skin effect (distribution Capacitor / inductance becomes larger), which can lead to signal degradation, data recognition is not correct, and if the data bus channel which is inconsistent line width will affect the data synchronization problem (resulting in inconsistent delay), in order to better control data signal Of the synchronization problem, so the data bus line appears in the serpentine line, which is to make the data channel within the delay in the more consistent.
Large area of ​​copper is for shielding interference and interference in terms of interference, double-sided panel can be used as a copper layer; and multilayer there is no problem with copper, because during which the power layer is very good to play Shielding and isolation.
3, multi-layer inter-layer layout
To the four-layer board as an example to illustrate the power should be positive / negative layer on the middle of the signal layer on the outside two lines, pay attention to the positive and negative power supply layer should not appear between the signal layer, the benefits of this approach is to do the most May allow the power layer to play the role of filtering / shielding / isolation, while PCB manufacturers to facilitate the production to improve the yield.
4, through the hole
Engineering design should minimize the design of the hole, because the hole will produce capacitance at the same time, but also prone to glitches and produce electromagnetic radiation. The hole diameter should not be large (this is for the electrical performance; but too small aperture will increase the difficulty of PCB production, commonly used 0.5mm / 0.8mm, 0.3mm as little as possible), small diameter in the copper process The probability of occurrence of burrs after the burr than the large aperture probability is small, which is due to drilling process.
5, software applications
Each software has its ease of use, but you are familiar with the degree of the software, PADS (POWER PCB) / PROTEL I have used, in a simple line (their familiar lines), I will use PADS directly Layout; and for the complex and new device lines, or first draw a good schematic diagram, with the form of a network table to do, to be correct and more convenient.
Layout PCB, some non-circular holes, the software is not the corresponding function to describe, I usually practice is to open a layer dedicated to the opening of the hole, and then draw the layer on the want to open Hole shape, of course, should be filled with painted wireframe, this is done in order to better PCB manufacturers to identify their own statements, and in the description of the document to explain.
6, PCB issued to the manufacturers to do
1) PCB computer files.
2) PCB file hierarchical program (each electronic engineer's drawing habits are different, Layout of the PCB file in the application of the layer will be different, so to attach a file your white oil / green oil / circuit diagram / Mechanical structure diagram / auxiliary hole diagram, make a correct list of documents to explain your wishes).
3) PCB production process requirements, you want to attach a document to illustrate the process to do the board: gold / copper / spray tin / broach fragrance, thickness specifications, PCB board material (flame retardant / non-flame retardant).
4) do the number of models.
5) of course, have to contact the contact and the person in charge.