What are the different layers in PCB and how to define them?

 Table of Contents

1.PCB Signal layer

2. PCB Internal plane layer

3.Mechanical layers in PCB

4.PCB Solder mask layer

5.printed circuit board (PCB) Paste mask layer

6. Keep out layers in PCB

7. PCB Silkscreen layer

8. PCB Multilayer layer

9. Drill layer layers in PCB

 

1. PCB 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. PCB Internal plane layer (internal power supply/grounding layer)

Protel 99 SE provides 16 internal power supply/grounding layers. This type of layer is only used for multilayer boards and is mainly used to arrange power and grounding wires. We call it two Layer, four-layer, and six-layer, generally refer to the number of signal layers and internal power/ground layers.

 

3. Mechanical layers in PCB (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.

PCB LAYER

 

4. PCB Solder mask layer (solder mask)

Coats a layer of paint, such as solder resist, on 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. Printed circuit board (PCB) Paste mask layer (solder paste protective layer, SMD patch layer)

 It has a similar role 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). Mainly for SMD components on the PCB. 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 paste mask file must be used for the steel mesh used for tinning, and the film 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 it is seen from the film picture. The two film images are very similar.

 

6. Keep out layers in PCB

Keep out layers in PCB is used to define the area where components and wiring can be effectively placed on the printed circuit board (PCB). Draw a closed area on this layer as the effective area for routing. Automatic layout and routing is not possible outside this area.

 

7. PCB Silkscreen layer (silkscreen layer)

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

 

8. PCB Multilayer (multi-layer)

The pads and penetrating vias on the 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 layers in PCB (Drilling layer)

The drilling layer provides drilling information during the circuit board manufacturing process (such as pads, via holes that need to be drilled). Protel 99 SE provides two drilling layers, Drillgride (drilling indication map) and Drill drawing (drilling drawing). The difference between solder mask and solder mask: solder mask refers to the part of the board that needs to be painted with green oil; because it is a negative output, the actual effect of the part with solder mask is not painted with green oil. It is tinned and silvery-white! The soldering layer: paste mask, which is used when the machine is patched and corresponds to the pads of all patch components. The size is the same as the top layer/bottom layer, and it is used to open the steel mesh. For tin. Key point: Both layers are used for soldering. It does not mean one is soldered and the other is green oil; then whether there is a layer refers to the green oil layer, as long as there is this layer on a certain area, it means this The area is insulated and green oil? For the time being, I have not encountered such a layer! The printed circuit board (PCB) we drew has a solder layer on the pad by default, so the pad part of the made PCB board is on It’s not surprising that the silver-white solder is not painted with green oil, but the traces on the PCB we drew only have the top layer or bottom layer, and there is no solder layer, but the traces on the finished PCB are all on. A layer of solder mask.

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