What is the purpose of the different layers of the circuit board?

The circuit board is composed of multiple layers, and the layer classification is mainly the number of electrical layers. The non-electrical layer is also present in every PCB.
What is the purpose of the different layers of the circuit board?
01 March 2024
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The circuit board is composed of multiple layers, and the layer classification is mainly the number of electrical layers. The non-electrical layer is also present in every PCB.

1.Mechanical Layers
What is mechanically finalized is the appearance of the entire PCB board. In fact, when we talk about the mechanical layer, we refer to the appearance structure of the entire PCB board. "Mechanical" means that it has no electrical properties, so it can be safely used to outline shapes, outline mechanical dimensions, place text, etc. It can also be used to design some physical and mechanical properties, such as borders, slots, openings, data marks, assembly instructions, etc.

2.Silkscreen Layers
The silk screen layer is divided into Top Overlay and Bottom Overlay, which are used to define the silk screen characters of the top and bottom layers. The silk screen layer is mainly used to place printed information, such as component names, component symbols, component pins, components The outlines and labels, various annotation characters and copyrights, etc., are convenient for future circuit welding and error checking. As shown below:

3.Disable wiring layer Keep out layer
Define an area on the circuit board where components and wiring can be effectively placed. Draw a closed area on this layer as an effective wiring area for constraints. For example, some places are not allowed to lay copper or have traces and vias, etc.

4.Signal layer
Used to route wires on circuit boards. Including Top layer (top layer) and Bottom layer (bottom layer), which are layers with electrical connections, where components can be placed and wiring can be laid out.

5.PasteMask Layers
The soldering flux layer is divided into the soldering flux top layer (Top paste) and the soldering flux bottom layer (Bottom paste). The soldering flux layer is used during machine placement and corresponds to the pads of all patch components. Generally, a layer of tin or gold plating on the pad of the PCB board is the soldering flux layer. This layer plays a role in assisting soldering.

6.SolderMask Layers
The solder resist layer is divided into top solder resist (Top Solder) and bottom solder resist (Bottom Solder). Generally, the green oil on the surface of the PCB board (the color of the board, commonly used ones are blue, black, white, red, yellow, etc.) is the solder mask, which plays an insulating role.

7.Internal power/ground layer Internal plane layer
Only used for multi-layer boards, mainly used for laying out power lines and ground wires. What we call double-layer boards, four-layer boards, and six-layer boards generally refer to the number of signal layers and internal power/ground layers.

8.Assembly Layers
The assembly layer is divided into the bottom assembly and the bottom assembly. Generally used during PCBA processing.

9.What is the difference between the function of the assembly layer and the silk screen layer?
The silk screen layer is for the people who manually attach the pieces and those who adjust the boards. The assembly layer is used to mark the position and direction of component assembly, indicating the physical size of the device, and is only used when the placement machine is welded.

10.Drill Layer
The drilling layer includes two drilling layers: Drill Gride (drilling instruction map) and Drill Drawing (drilling map). The drilling layer is used to provide drilling information during the circuit board manufacturing process.

Summary
The circuit board is composed of mechanical layer, silk screen layer, forbidden wiring layer, signal layer, soldering layer, solder mask layer, internal power/ground layer, assembly layer and drilling layer. Each layer has different purposes.
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