PCB has many classifications and different classification standards, such as single-layer, double-layer and multi-layer according to the number of layers, rigid PCB and flexible PCB according to material, and PCB of various other materials. In this article, the definition, function, application, design and manufacture of multilayer PCB will be introduced.
What is a multilayer PCB?
Multilayer PCB is a printed circuit board with a special structure formed by superimposing multiple layers of conductive substrates. It achieves high integration and high performance by laminating multiple independent circuits together. Compared with single-layer circuit boards, multi-layer circuit boards have higher reliability, lower delay and better electromagnetic compatibility.
How many layers can a PCB have?
PCB boards can be divided into three categories according to the number of layers: 1-4 layers, 6-8 layers and more than 10 layers. Commonly used are 1-4 layers and 6-8 layers, while more than 10 layers are industrial-grade high-density interconnection boards (HDI boards).
Among them, PCB boards with 1-4 layers are the most common and simplest, and are generally used in some simple electronic products, which are easy to manufacture, maintain and locate. PCB boards with 6-8 layers are more common in intelligent products, and the circuit complexity and efficiency are significantly improved. PCB boards with more than 10 layers can be used in high-speed, high-density, high-reliability products, such as Internet servers, high-end mobile communication equipment, etc.
Why are multilayer PCB needed?
1.Improve performance: Multilayer PCB can integrate multiple functional modules in a compact structure, thereby improving the performance of the entire device. For example, in a smart phone, core components such as the processor, memory, and storage on the motherboard can be integrated on one or several layers of PCB.
2. Reduce cost: By reducing the number of layers and simplifying the design, multilayer circuit boards can reduce production costs. In addition, due to its high reliability and durability, multilayer circuit boards can maintain stable performance for a long period of time, thereby reducing the cost of maintenance and replacement.
3. Improve reliability: The design of multi-layer circuit boards makes faults easier to detect and repair. When a problem occurs in one circuit layer, the problem can be solved by replacing the layer without affecting the normal operation of the entire system. In addition, multilayer circuit boards can also adopt more protective measures, such as gold plating layer, via insulation layer, etc., to improve anti-interference ability and electrical performance.
4. Support high-density integration: With the development of integrated circuits, modern electronic products have higher and higher requirements for the number and size of components on the circuit board. Multilayer PCBs can achieve a higher level of integration, thereby accommodating more components and meeting these needs.
5. Promote innovation: Multilayer PCBs provide designers with greater design space, enabling them to create more creative and high-performance products. For example, some high-end audio systems and professional cameras use complex multi-layer circuit board designs.
In short, as a key component in electronic products, multilayer PCBs play an important role in improving performance, reducing costs, and improving reliability. With the continuous development of science and technology, we have reason to believe that multilayer PCBs will continue to play an increasingly important role in future electronic equipment.
What are the layers of a multilayer PCB?
Multilayer PCB is a printed circuit board with multiple inner layers. By establishing electrical connections between different inner layers, the combination and integration of various functional modules can be realized. Its structural composition mainly includes the following parts:
1. Signal layer: The signal layer is the core part of the multilayer PCB, mainly used to carry various electronic components, such as resistors, capacitors, inductors, diodes, transistors, etc. The thickness and material selection of the signal layer directly affect the performance and reliability of the circuit. Common signal layer materials include FR-4, Rogers, Isola, and the like.
2. Power layer: The power layer is mainly responsible for providing stable DC power for each functional module. According to needs, the power supply layer can be divided into +Vcc (positive power supply), -Vcc (negative power supply), +GND (ground) and -GND (ground) and so on. The layout and design of the power planes are critical to the overall circuit performance.
3.Internal plane layers: The Internal plane layers is used to connect the common ground between each functional module to achieve good electromagnetic compatibility (EMC). The material and layout of the formation play an important role in reducing interference noise and improving system stability. Common formation materials include FR-4, Rogers, etc.
4. Top layer and bottom layer: The top layer and bottom layer are located on the outermost and innermost layers of the multilayer PCB, and are usually used to install fixed metal contacts, such as sockets, plugs, antennas, etc. In addition, the top layer can also be used to install auxiliary components such as panel indicators and buttons.
When designing a multilayer PCB, it is necessary to fully consider the electrical connection and interference between the layers. For example, the connection between the signal layers should minimize crosstalk and reflection; the layout of the power layer and the ground layer should avoid mutual interference; the design of the top layer and the bottom layer should meet the requirements of fixed interfaces, etc. Through reasonable structural design and hierarchical division, electronic products with high performance and high reliability can be realized.
In short, multilayer PCB is an important part of modern electronic technology, and its structure and layer design are of great significance for improving product performance.
What are the applications of multi layer PCB?
With the development of science and technology, multilayer PCBs have become an indispensable part of modern electronic equipment. It can achieve higher signal transmission efficiency and higher functional density by designing multiple circuit layers on the same panel. This performance makes multilayer PCB circuit boards widely used in various application fields.
1. Communication
Multilayer PCBs are widely used in the communication field. For example, the motherboard used in mobile phones is a multilayer PCB. Mobile devices need to integrate multiple components in an extremely limited space, including processors, memories, communication modules, etc. Multilayer PCB can meet these requirements, and can also provide faster data transmission speed and more stable signal transmission.
2. Industrial control
Multilayer PCBs are also widely used in industrial automation control systems. These systems usually require high-speed data transmission and complex control logic, but also need to operate under harsh environmental conditions. Multi-layer PCB can provide higher anti-interference ability and higher reliability, making the industrial control system more stable and reliable.
3. Medical devices
Medical equipment requires highly sophisticated electronic control and signal processing, which requires higher performance and stability of the circuit board. Multi-layer PCBs can achieve more complex functional integration, and can provide higher data transmission speed and higher anti-interference ability, making medical equipment safer and more reliable.
4. Aerospace
In the field of aerospace, multilayer PCBs also play an important role. For example, circuit boards used in flight control systems must have extremely high reliability and anti-jamming capabilities to ensure the safety of the aircraft. Multi-layer PCB circuit boards can achieve higher signal transmission efficiency and higher reliability, making the flight control system safer and more reliable.
5. Automotive electronics
With the development of automotive electronics, multi-layer PCBs have gradually become an indispensable part of automotive electronics. For example, circuit boards used in car entertainment systems must have high-speed data transmission and complex control logic, and also need to work under harsh environmental conditions. Multi-layer PCB can provide higher anti-interference ability and higher reliability, making the car entertainment system more stable and reliable.
What's multilayer PCB design?
1. Preliminary scheme design
Before designing the multilayer PCB, the functional requirements of the circuit should be clarified first, and then the preliminary scheme design should be carried out according to the requirements. The main task at this stage is to determine the basic structure and main modules of the circuit.
2. Schematic drawing
On the basis of the preliminary scheme design, draw the schematic diagram. The schematic diagram is an important basis for guiding the design of the subsequent multilay PCB , so the accuracy and integrity of the schematic diagram should be ensured.
3. Formulation of detailed design plan
After the schematic diagram is drawn, a detailed design scheme is formulated according to the schematic diagram. The main tasks at this stage include: selecting appropriate PCB materials, determining the wiring strategy of the circuit, and formulating a list of components.
4. Multilayer PCB drawing
After completing the detailed design plan, start to draw the multilayer PCB. At this stage, it is necessary to pay attention to issues such as signal integrity and radio frequency design to ensure that the performance of the multilayer PCB meets the design requirements.
How is multilayer PCB made?
In the manufacturing preparation stage, it is necessary to prepare the materials and equipment required for manufacturing, including substrate materials, chemicals, photolithography machines, etching machines, drilling machines and other equipment. In addition, relevant process documents and manufacturing plans need to be prepared.
Printing structure
The printed structure is the first step in the manufacture of multilayer circuit boards, and its purpose is to form multilayer copper foil on the substrate. The printed structure process includes:
1) Drilling, drilling the inner layer positioning holes and electrical connection holes of the substrate.
2) Chemical copper, which forms a thin layer of copper on the surface of the substrate through a chemical reaction for subsequent etching.
3) Coating photoresist, coating the photoresist on the surface of the substrate for making circuit patterns.
4) Photolithography, transfer the circuit pattern to the photoresist layer through photolithography technology.
5) Etching, chemically etching away the copper foil outside the photoresist layer to form a circuit pattern.
Stacking
After the printed structure is completed, multiple copper foils need to be stacked together to form a multilayer circuit board.
Stacking process includes:
1) Align, align and press each layer of copper foil together.
2) Pre-pressing, the copper foils are compressed together through a pre-pressing process.
3) Pressing, the copper foils are completely pressed together by means of high temperature and high pressure.
Molding
After the stacking is completed, the multi-layer circuit board needs to be cut into the desired shape and size through a forming process. The molding process includes:
1) Drilling, drill the required holes out of the entire circuit board.
2) Edge milling, trim the edge of the circuit board into the desired shape.
3) Divide the board, divide the whole circuit board into several separate circuit boards.
Surface treatment
In order to protect the surface of multilayer circuit boards and prolong their service life, surface treatment is required. Surface treatment process includes:
1) Electroless gold plating, a layer of metal is plated to improve its corrosion resistance.
2) Spray the mask and spray a protective layer to prevent the surface of the circuit board from being damaged.
Final inspection
After the manufacturing is completed, a final inspection is required to ensure that the quality of the multilayer PCB meets the requirements. The final inspection process includes:
1) Appearance inspection, check whether the surface of the circuit board is smooth, without scratches, without deformation, etc.
2) Electrical performance test, to test whether the electrical performance of the circuit board meets the requirements.
3) Reliability test, to test whether the reliability of the circuit board meets the requirements.
Through the above technological process, high-quality, high-reliability multilayer circuit boards can be manufactured, which can be used in various electronic products.
Conclusion
To sum up, we have known about the roles, structure, design and manufacturing of multilayer PCB. Multilayer PCBs are widely used in the fields of communication, industrial control, medical equipment, aerospace and automotive electronics. With the continuous development of science and technology, the application fields of multilayer PCB will become more and more extensive.
A Multilayer PCB (Printed Circuit Board) is a type of circuit board that consists of multiple layers of conductive copper foil separated by insulating materials (dielectrics). These boards are used to connect and support electronic components.
Multilayer PCBs can have various numbers of layers, typically ranging from 4 layers up to 20 or more, depending on the complexity and requirements of the electronic circuit.
The manufacturing process for Multilayer PCBs involves:
Layer Stackup Design: Determining the arrangement of copper layers and dielectric materials.
Copper Cladding: Applying copper foil to both sides of each core layer.
Lamination: Bonding the layers together under heat and pressure to form a solid panel.
Drilling: Creating holes (vias) to connect copper layers.
Plating and Etching: Depositing and etching copper to create circuit patterns.
Surface Finishing: Applying a protective layer (e.g., solder mask) and final finishing.
