The meaning of layers in the PCB

1. What is the meaning of each layer in the PCB?

Mechanical layer: defines the appearance of the entire PCB board, that is, the overall structure of the PCB board.

Keepoutlayer Disables the wiring layer: Defines the copper side of the cloth’s electrical characteristics. That is to say, after defining the disabling of the wiring layer, in the course of the subsequent cloth-laying, the line having the electrical characteristics may not exceed the boundary of the disabling wiring layer.

Top overlay Top Bottom Screen & Bottomoverlay bottom screen: The silkscreen characters defining the top and bottom are the component numbers and characters commonly seen on the PCB.

Top paste Top Pad Layer & Bottomppad: This is the exposed copper pad that we can see.

Top solder Top Solder Mask & Bottomsolder Bottom Solder Mask: Contrary to top paste and bottom paste, it is a layer that is covered with green oil.

Drill guide via guide layer:

Drilldrawing hole drilling layer:

Multiplayer Multilayer: Refers to all layers of the PCB.

2. How to use power PCB to set the layer of 4 layers?

Layer definition can be set to

1:no plane+ component(top route)

2: cam plane or split/mixed (GND)

3: cam plane or split/mixed(power)

4: no plane + component (if the single plane element can be defined as noplane+route)


The cam plane generates a power supply and the ground plane is negative, and cannot be routed on this layer, and the split/mixed generates a positive film, and the layer can be used as a power source or ground, and can also be routed in this layer (recommendation in the power layer and stratum) Traces, as this will destroy the integrity of the layer, may cause EMI problems). Add the power network (such as 3.3V, 5V, etc.) from the left-hand list to the right-hand list in the layer 2 assignment, thus completing the layer definition

3.”Implement signal integrity analysis, formulate corresponding wiring rules, and perform wiring according to these rules.” How does this sentence be understood?

Before the simulation analysis, a series of layout and wiring strategies to achieve signal integrity can be obtained. Often these strategies translate into some physical rules that constrain the layout and routing of the PCB. The usual rules are topological rules, length rules, impedance rules, parallel spacing and parallel length rules, and so on. The PCB tool can complete the wiring under these constraints. Of course, the effect of the completion is still known through post-emulation verification.

4. Assuming a 4-layer board, the middle two layers are VCC and GND, the trace goes from top to bottom, and the return path from BOTTOMSIDE to TOP SIDE is via this signal VIA or POWER?

There is no clear statement about the return path of the signal on the via. It is generally believed that the return signal will return from the nearest ground or the via of the power supply. In general simulation, EDA tools treat the vias as a fixed lumped parameter RLC network, which is, in fact, a worst-case estimate.

5. use PROTEL to draw the schematic diagram, the netlist produced when making the board has always been wrong, can’t produce PCB board automatically, why is it?

The generated netlist can be manually edited based on the schematic, and the automatic routing can be performed after the check is passed. Plates that are automatically laid out and routed with board software are not ideal. The error in the network table may be that the component package in the schematic is not specified; it may also be that the library in the distribution board does not contain all the component packages in the specified schematic. If it is a single panel, do not use automatic wiring. The double panel can be used for automatic wiring. It is also possible to manually and other automatic signals on the power supply and important signal lines.

6. how to choose PCB software?

Select the PCB software according to your needs. There is a lot of high-level software available in the market. The key is to see if it suits your design capabilities, design size, and design constraints. The knife is fast and easy to use. Too fast will hurt your hand. To find an EDA manufacturer, please make a product introduction in the past. Everyone sat down and talked about it. Whether you buy it or not, you will gain something.

7. how to draw bound IC in PROTEL?

Specifically, the mechanical layer picture is used in the PCB, and the IC substrate lining is based on IC SPEC. The decision is to connect vccgndfloat and the mechanical layer can be print bonding drawing.

8, how to understand the concept of broken copper, floating copper?

From the perspective of PCB processing, copper foils with an area smaller than a unit area are generally called broken copper. These two small copper foils may cause problems due to etching errors during processing. From an electrical point of view, the copper foil that does not have any DC network connection is called floating copper, and the floating copper will have an antenna effect due to the influence of surrounding signals. Floating copper may be broken copper, or it may be a large area of the copper foil.

9. Is there a relationship between near-end crosstalk and far-end crosstalk and the frequency of the signal and the rise time of the signal?

Will they change as they change? If there is a relationship, can there be a formula to explain the relationship between them?

It should be said that the cross-talk caused by the infringing network to the victim network is related to the change of signal, and the faster the change, the greater the crosstalk caused (V=L*di/dt). The effect of crosstalk on the decision of the digital signal on the victim network is related to the frequency of the signal. The faster the frequency, the greater the impact.

10, PCB and PCB connection, usually by inserting gold or silver “finger” to achieve, if the “finger” and socket contact bad how to do?

If it is a cleaning problem, clean it with a special electrical contact cleaner or use a writing eraser to clean the PCB. Also consider whether 1, whether the gold finger is too thin, whether the pad is not consistent with the socket; 2. if the socket is in loose perfume or impurities; 3. whether the quality of the socket is reliable.

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