PCB has many layers. When beginners learn PCB design, they are easily confused by various layers. To this end, we have made a summary of the layers in the PCB to help everyone better understand and master.

Definition of layers in PCB design

1. Mechanical Layers

The mechanical layer is generally used to place indicative information about board manufacturing and assembly methods, such as PCB dimensions, size marks, data materials, via information, assembly instructions and other information.

2. Keep Out Layer is prohibited

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

3. Silkscreen layer

The silk screen layer is the text layer, which belongs to the top layer in the PCB, and is generally used for annotations.

3.1 Top Overlay

It is used to mark the projection outline of the component, the label of the component, the nominal value or model, and various annotation characters.

3.2 Bottom Overlay

Same as the top silk screen layer, if all the marks on the top silk screen layer are included, the bottom silk screen layer can be closed.

4. Solder Mask

The solder mask refers to the part of the printed circuit board to be painted with green oil. In fact, this solder mask uses a negative output, so after the shape of the solder mask is mapped to the board, it is not the green solder mask, but the copper skin is exposed.

5. Multi Layer

The pads and penetrating vias on the circuit board have to penetrate the entire circuit board and establish electrical connections with different conductive pattern layers. Therefore, the system is specially set up with an abstract layer-multi-layer. Generally, the pads and vias must be arranged on multiple layers. If this layer is closed, the pads and vias cannot be displayed.

6. Drill Layer

The drilling layer provides drilling information during the circuit board manufacturing process (such as pads and vias require drilling).

7. Signal Layers

7.1 Top Layer

Also called component layer, it is mainly used to place components. For double-layer boards and multilayer boards, it can be used to arrange wires or copper.

7.2 Bottom Layer

Also called soldering layer, it is mainly used for wiring and soldering. It can be used to place components for double-layer boards and multilayer boards.

7.3 Mid-Layers

There can be up to 30 layers, which are used to arrange signal lines in a multilayer board. Power lines and ground lines are not included here.

8. Internal Planes

Usually referred to as the inner electric layer, it only appears in multilayer boards. The number of PCB layers generally refers to the sum of the signal layer and the inner electric layer. Same as the signal layer, the inner electric layer and the inner electric layer, and the inner electric layer and the signal layer can be connected to each other through through holes, blind holes and buried holes.

How many layers is the best PCB design?

According to the number of circuit layers, PCB boards can be divided into single-sided PCB circuit boards, double-sided PCB circuit boards and multilayer PCB circuit boards. So, in PCB design, how many layers are the best?

In fact, there is no uniform answer. Instead, PCB designers need to weigh how many layers to choose for design based on the complexity of the entire circuit being designed, which is mainly determined by the difficulty of the core components in the entire project and the ease of component layout.