Briefly describe the role of each layer in the PCB board and the precautions in use

Many PCB board design enthusiasts, especially beginners, are not very familiar with the various layers of PCB design. I don’t know the role and usage. Here is a systematic explanation for everyone:

  1. Mechanical layer As the name suggests, it is the appearance of the entire PCB board. In fact, when we say the mechanical layer, it refers to the overall structure of the PCB board. It can also be used to set the board’s form factor, data marks, alignment marks, assembly instructions, and other mechanical information. This information varies depending on the requirements of the design company or PCB manufacturer. In addition, the mechanical layer can be attached to other layers to output the display together.
  2. The Keep out layer is used to define the area on the board where components and wiring can be placed efficiently. A closed area is drawn in this layer as the effective area of the wiring, and it is not automatically laid out and routed outside the area. The banned wiring layer is the boundary when we define the copper characteristics of the electrical properties of the cloth. That is to say, after we have defined the banned wiring layer, we can not extend the wiring of the electrical characteristics in the future cloth. Layer boundaries, often used to use the Keep out layer as a mechanical layer, this method is actually wrong, so it is recommended that you make a distinction, otherwise the board factory will give you a property change every time you produce.
  3. Signal layer: The signal layer is mainly used to lay out the wires on the circuit board. Includes Top layer, Bottom layer, and 30 mid layer. The top layer and the Bottom layer are placed in the device, and the inner layer is routed.
  4. Top paste and Bottom pastes are the top and bottom pad steel mesh layers, and the size of the pads is the same. This is mainly because we can use these two layers to make the steel mesh when we do SMT. Just dig a hole of the size of the pad on the net. We put the stencil on the PCB and brush it evenly with a brush with solder paste.

5. Top Solder and Bottom Solder This is a solder mask, to prevent green oil coverage, we often say “open the window”, the conventional copper or trace is the default green cover, if we correspond to the solder mask If it is handled, it will prevent the green oil from covering and will expose the copper.

6. Internal plane layer (internal power / ground layer): This type of layer is only used for multi-layer boards, mainly used to arrange power lines and grounding lines, we call double-layer board, four-layer board, six-layer board, generally refers to The number of signal layers and internal power/ground planes.

  1. Silkscreen layer: The silkscreen layer is mainly used for placing printed information, such as the outline and label of components, various annotation characters, and so on. Altium offers two silkscreen layers, Top Overlay and Bottom Overlay, with top-level silkscreen files and bottom-screen silkscreen files.
  2. Multi layer: The pads on the board and the through vias penetrate the entire board and establish electrical connections with different conductive patterns. Therefore, the system has an abstract layer—multilayer . Generally, the pads and vias are placed on multiple layers. If this layer is turned off, the pads and vias cannot be displayed.
  3. Drill Drawing: The drilled layer provides drilling information during the manufacturing process of the board (such as pads and vias that require drilling). Altium offers two drilled layers, Drill grides and Drill drawing.




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