In PCB circuit board design, the definition of PCB layer is as follows:

　　 1. Top layer (Top Layer):

　　 is also called component layer, which is mainly used to place components, and it can be used for wiring of laminates and multilayer boards;

　　2. Mid Layer: There can be up to 30 layers, which are used to route signal lines in multilayer boards.

　　 3. The bottom signal layer (Bootom Layer):

　　 is also called the solder layer, mainly used for wiring and soldering, and sometimes components can be placed

　　4. Top Overlayer:

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

　　5. Bottom Overlayer:

　　 has the same function as the top silk-screen layer, if all kinds of labels are contained in the top silk-screen layer, then the bottom silk-screen layer is not needed.

　　 6. Internal power plane (Internal Plane):

　　 is usually called the internal electrical layer, including the power supply layer, the reference power layer and the ground plane signal layer. The internal power layer is output in negative form.

Definition of PCB layer

　　7. Mechanical Layer (Mechanical Layer):

　　 defines the layer of mechanical data of the circuit board in the design. The definition of the mechanical shape of the circuit board is realized through a certain mechanical layer design.

　　 8. Solder Mask (Solder Mask welding surface):

There are two layers, Top solder Mask and Bootom Solder mask, which are automatically generated by ProtelPCB corresponding to the pad and via data in the circuit board file. It is mainly used to lay the resist Solder paint. This board layer uses negative output, so the pads and vias displayed on the board layer represent the areas on the circuit board where solder mask is not applied, that is, the parts that can be soldered.

　　 9. Solder paste layer (Past Mask-Surface soldering surface):

There are two layers, Top Past Mask and Bottom Past Mask, which are used to correspond to the solder joints of SMD components during the soldering furnace, and are also output in negative form. The pads displayed on the board And the via part represents the area on the circuit board where solder paste is not spread, that is, the part that cannot be soldered.

　　10. Keep Ou Layer:

　　 defines the wiring area where the signal line can be placed, and places the signal line into the function range defined by the bit.

　　11. MultiLayer:

　　 usually appears in combination with via or through-hole pad design to describe the layer characteristics of the void.

　　12. Drilling data layer (Drill):

　　·Solder means whether to resist soldering, that is, whether there is copper exposed on the PCB

　　·Paste is used to open steel mesh, whether to open steel mesh

　　 Therefore, when drawing the board, both layers must be painted. Solder is for the PCB board to have no green oil to cover the exposed copper), and the paste is for opening the stencil, which can be painted with solder paste.