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PCB Tech
The definition of each layer of the PCB circuit board
PCB Tech
The definition of each layer of the PCB circuit board

The definition of each layer of the PCB circuit board

2021-10-25
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Author:Downs

The mechanical layer defines the appearance of the entire PCB circuit board, and the mechanical layer refers to the overall structure of the PCB board. The forbidden wiring layer is to define the boundary when we lay out the copper with electrical characteristics, that is to say, after the forbidden wiring layer is defined first, in the subsequent threading, the wiring with electrical characteristics cannot exceed the forbidden wiring layer. The boundary. topoverlay and bottomoverlay are the silk screen characters that define the top and bottom, which are the component numbers and some characters that we generally see on the PCB. Toppaste and bottompaste are the top and bottom pad layers, which refer to the copper platinum that can be seen exposed, (for example, a wire is drawn on the top wiring layer, and the wire is only a wire seen on the PCB. Only, it is covered by the whole green oil, but draw a square or a dot on the toppaste layer at the position of this line, the square and this dot on the printed board will have no green oil, and It is copper platinum. The two layers of top solder and bottomsolder are just opposite to the previous two layers. It can be said that these two layers are the layers to be covered with green oil. The multilayer layer is actually almost the same as the mechanical layer., This layer refers to all layers of the PCB board.

The two layers of top solder and bottomsolder are just opposite to the previous two layers. It can be said that these two layers are the layers to be covered with green oil; because it is a negative output, the actual effect of the solder mask is actually not Green oil, but tin plated, silvery white!

pcb board

1 Signal layer

The signal layer is mainly used to arrange the wires on the circuit board. Protel 99 SE provides 32 signal layers, including Top layer (top layer), Bottom layer (bottom layer) and 30 MidLayer (middle layer).

2 Internal plane layer (internal power/ground layer)

Protel 99 SE provides 16 internal power planes/ground planes. This type of layer is only used for multilayer boards, and is mainly used to arrange power and ground wires. It is called double-layer board, four-layer board, and six-layer board, which generally refers to the number of signal layers and internal power/ground layers.

3 Mechanical layer (mechanical layer)

Protel 99 SE provides 16 mechanical layers, which are generally used to set the external dimensions of the circuit board, data marks, alignment marks, assembly instructions and other mechanical information. This information varies depending on the requirements of the design company or PCB manufacturer. Executing the menu command Design|MechanicalLayer can set more mechanical layers for the circuit board. In addition, the mechanical layer can be added to other layers to output and display together.

4 Solder mask layer (solder mask layer)

Apply a layer of paint, such as solder resist, to all parts other than the pad to prevent tin on these parts. The solder mask is used to match the pads during the design process and is automatically generated. Protel 99 SE provides two solder masks, Top Solder (top layer) and Bottom Solder (bottom layer).

5 Paste mask layer (solder paste protection layer, SMD patch layer) It has a similar function to the solder mask, but the difference is the corresponding surface-pasted component pads during machine soldering. Protel99 SE provides two protective layers of solder paste, Top Paste (top layer) and Bottom Paste (bottom layer).

is mainly for SMD components on PCB boards. If all Dip (through hole) components are placed on the board, there is no need to export Gerber files on this layer. Before attaching SMD components to the PCB board, solder paste must be applied to each SMD pad. The stencil used for tinning must require this Paste Mask file before the film can be processed.

The most important point of the Gerber output of the Paste Mask layer is to be clear, that is, this layer is mainly for SMD components. At the same time, compare this layer with the Solder Mask described above to find out the different functions of the two, because you can see from the film picture. The two film images are very similar.

6 Keep out layer (prohibited wiring layer)

is used to define the area where components and wiring can be effectively placed on the PCB design. Draw a closed area on this layer as the effective area for routing. Automatic layout and routing is not possible outside this area.

7 Silkscreen layer

The silk screen layer is mainly used to place printed information, such as component outlines and labels, various annotation characters, etc. Protel 99 SE provides two silk screen layers, Top Overlay and Bottom Overlay. Generally, all kinds of marked characters are on the top silk screen layer, and the bottom silk screen layer can be closed.

8 Multi layer (multi-layer)

The pads and penetrating vias on the PCB circuit board must penetrate the entire circuit board and establish electrical connections with different conductive pattern layers. Therefore, the system specifically sets up an abstract layer-multilayer. Generally, the pads and vias must be arranged on multiple layers. If this layer is turned off, the pads and vias cannot be displayed.

9 Drill layer (drilling layer)

The drilling layer provides drilling information during the PCB manufacturing process (such as pads, vias need to be drilled). Protel 99 SE provides two drilling layers, Drillgride (drilling indication map) and Drill drawing (drilling drawing).