Multilayer PCB board is an electronic component with multiple conductive layers, which is widely used in electronic equipment. The working principle of multi-layer PCB board is different from that of single or double layer PCB board, and its main feature is to increase the internal conductive layer, thereby improving the complexity and integration of the circuit.
1. The working principle of multi-layer PCB board
1.1 Basic structure of multi-layer PCB board
The multi-layer PCB board consists of a plurality of conductive layers, insulating layers and outer layers. The conductive layer is usually made of copper foil and is used to connect electronic components; The insulation layer is made of Prepreg or resin-based material to isolate the conductive layer; The outer layer is usually composed of copper foil and resin-based materials to protect the circuit board and provide an additional conductive path.
1.2 Conductive layer of multi-layer PCB board
The conductive layer of a multi-layer PCB board can be divided into an internal conductive layer and an external conductive layer. The internal conductive layer is located between the insulating layers and is used to connect circuits at different levels; The external conductive layer is located on the surface of the board and is used to connect the electronic components and provide additional conductive paths.
1.3 Signal transmission of multi-layer PCB board
In the multi-layer PCB board, the signal transmission is mainly carried out through the conductive layer. Signal sources (such as microprocessors, amplifiers, etc.) transmit signals to target devices (such as displays, speakers, etc.) through conductive layers. The transmission speed of the signal in the conductive layer is affected by the material, thickness and layout of the conductive layer.
1.4 Electromagnetic compatibility of multi-layer PCB board
The design of multilayer PCB boards needs to consider electromagnetic compatibility (EMC) issues. Electromagnetic compatibility refers to the ability of electronic devices to work properly in an electromagnetic environment, including the ability to resist interference and the ability to emit interference. In order to improve electromagnetic compatibility, the design of multi-layer PCB boards needs to use appropriate layout, ground design and shielding technology.
2. Design method of multi-layer PCB board
2.1 Preparation before design
Before designing a multi-layer PCB board, it is necessary to analyze the function, performance requirements and working environment of the circuit in order to determine the appropriate design scheme. In addition, it is also necessary to collect the electrical parameters and physical dimensions of the individual components in the circuit for reasonable layout and wiring.
2.2 Layout Design
Layout design is an important part of multi-layer PCB board design, the main purpose is to rationally arrange the location of electronic components to meet the performance requirements of the circuit and manufacturing process requirements. Layout design needs to consider the following aspects:
▪ Relative position between components: According to the function and performance requirements of the circuit, the relative position between components is reasonably arranged to reduce the delay and interference of signal transmission.
▪ The connection between the component and the conductive layer: the connection between the component and the conductive layer is rationally selected to reduce the connection resistance and improve the stability of signal transmission.
▪ Heat dissipation of components: Considering the heat dissipation requirements of components, reasonably arrange the location of components and heat dissipation channels to ensure the stability and reliability of the circuit.
2.3 Wiring Design
Wiring design is another important part of multi-layer PCB board design, the main purpose is to reasonably connect electronic components to achieve the function of the circuit. Wiring design needs to consider the following aspects:
▪ Signal transmission path: According to the function and performance requirements of the circuit, the signal transmission path is reasonably selected to reduce the delay and interference of signal transmission.
▪ Conductor width and spacing: According to the size of the current and the frequency of the signal, the reasonable choice of conductor width and spacing to ensure the stability of signal transmission and electromagnetic compatibility.
▪ Ground wire design: Reasonable design of ground wire to improve circuit stability and electromagnetic compatibility. Ground cables can be divided into single-point grounding, multi-point grounding and hybrid grounding.
2.4 Power Supply and Ground cable design
Power supply and ground design is a key part of multi-layer PCB board design, the main purpose is to provide a stable power supply and good grounding for the circuit. Power supply and ground design need to consider the following aspects:
▪ Power distribution: According to the power consumption of the circuit and the stability of the power supply requirements, reasonable distribution of power to ensure the normal operation of the circuit.
▪ Ground wire layout: Reasonable ground wire layout to improve circuit stability and electromagnetic compatibility. Ground lines can be planar, grid or hybrid layout.
▪ Isolation of power and ground: In multi-layer PCB boards, the power and ground need to be reasonably isolated to reduce the impact of power noise and ground rebound on the circuit.
3. Multi-layer PCB board manufacturing process
3.1 Manufacturing Process
The manufacturing process of multi-layer PCB board includes multiple steps, such as inner layer production, outer layer production, lamination, drilling, copper plating, graphic transfer, etching, film removal, surface treatment, etc. The following is a detailed description of the manufacturing process:
▪ Inner layer production: The first production of the inner conductive layer, usually the composite structure of copper foil and prepreg.
▪ Outer layer: The outer conductive layer is made on the surface of the inner conductive layer, usually using a composite structure of copper foil and resin-based materials.
▪ Laminating: The inner and outer conductive layers are bonded together through the laminating process to form the basic structure of the multi-layer PCB board.
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