PCB Blog - What is the structure of the PCB board layers?

PCB board layers are the different structural layers used in circuit board design. These layers define the various functions and information of the circuit board, such as signal, power, soldermask and mechanical layers. The combination of these layers allows the PCB to efficiently transmit signals and distribute power in complex electronic devices.

The common structures of PCB  board layers include single-layer boards, double-layer boards, and multi-layer boards.

1.Single layer board: A circuit board with only one side coated with copper and the other side not coated with copper. Usually, components are placed on the side without copper coating, which is mainly used for wiring and welding.

A single panel is the simplest form of PCB board, with only one side covered with copper foil. A single panel is suitable for simple circuits such as electronic clocks, toys, etc. The production process of a single panel is simple and cost-effective, but its functions are relatively simple.

2.Double layer board: A circuit board with copper coated on both sides, usually referred to as the top layer on one side and the bottom layer on the other side. Generally, the top layer is used as the surface for placing components, and the bottom layer is used as the welding surface for components.

The production of double-sided panels is more complex than that of single panels,but easier to manufacture than multi-layer panels. Double-sided boards are suitable for circuits of medium complexity, such as audio, television, etc. The production of dual panels is flexible,and components can be arranged on both sides of the board.

3.Multilayer board: A circuit board containing multiple working layers, including several intermediate layers in addition to the top and bottom layers. Typically, the intermediate layer can serve as a wire layer, signal layer, power layer, grounding layer, etc. Layers are insulated from each other, and the connection between layers is usually achieved through holes.

The production of multi-layer boards is more complex than that of double panels, but it can improve the density and performance of the circuit. Multilayer boards are suitable for high-density, high-speed, and high-frequency circuits, such as computers, mobile phones, etc. Multilayer boards can increase the number of layers as needed to improve circuit performance.

Detailed introduction to PCB board layers

PCB is an indispensable part of modern electronic devices, playing a role in connecting, transmitting signals, supporting and protecting electronic components in electronic devices.PCB is usually composed of multiple layers of PWB, each with different functions and characteristics.

1.Signal Layer

The signal layer is the most important in the PWB board,which is the main layer connecting various components.On the signal layer,circuits,signal transmission lines,power lines,and grounding wires are usually arranged.The wiring design of the signal layer directly affects the performance and reliability of the entire PCB.

2.Power Layer

The power layer is a layer in the printed wiring board that is mainly used to connect the power supply and ground wire. On the power layer, power and ground wires are usually arranged to ensure a stable and reliable power supply for the entire PCB.

3.Ground Layer

The ground wire layer is also a layer in the printed circuit board, mainly used to connect the ground wires of various components. On the ground wire layer, grounding and power lines are usually arranged to ensure stable and reliable ground wire connections throughout the entire PCB.

4.Pad Layer

The pad layer is a layer in a circuit board that is mainly used to connect components and printed circuit boards.On the pad layer, pads and sockets are usually arranged to allow components to be connected to the printed wiring board.

5.Assembly Layer

The assembly layer is a layer in a PCB board, mainly used for assembling components. On the assembly layer, the installation positions and methods of components are usually arranged for PCB manufacturers to assemble and weld components.

6.Solder Mask Layer

The solder mask layer is a layer in the PCB board, mainly used to prevent short circuits and poor soldering during the welding process. On the solder layer, a layer of green paint is usually applied to protect the PCB  from chemical corrosion and mechanical damage.

7.Copper Layer

The copper-clad layer is a layer in a PCB  that is mainly used to provide circuit connections and support. On the copper-clad layer, circuits and signal transmission lines are usually arranged to ensure stable and reliable circuit connection of the entire PCB.

In summary,each pcb board layers have different functions and characteristics. In the design and manufacturing process of a PCB, it is necessary to fully consider the requirements and limitations of each layer to ensure the performance and reliability of the PCB.

When selecting a PCB design layer, the following issues should be considered

1.Purpose

Where will the PCB be used? PCB is used in various types of simple to complex electronic devices. Therefore, the first step is to clarify whether the application has minimal functionality or complex functionality.

2.Required signal type

The selection of the number of layers also depends on the type of signal they need to transmit. The signals are divided into high-frequency, low-frequency, ground or power sources. For applications that require multiple signal processing,multi-layer PCBs are required, and these circuits may require different grounding and isolation.

3.Type of through-hole

The selection of through holes is another important factor to consider. If you choose to bury through holes, more internal layers may be required, so it can meet the multi-layer requirements accordingly.

4.The density and number of required signal layers

The determination of the PCB layer is also based on two important factors: signal layer and pin density. The number of layers in a PCB increases as the pin density decreases. The pin density is 1.0. For example, a pin density of 1 would require 2 signal layers. However, pin density<0.2 may require 10 layers or more.

Reasons to use multilayer printed circuit boards

In recent years, with the development of electronic products towards miniaturization, high performance and high integration, the use of multilayer printed circuit boards (PCBs) has gradually replaced single-layer PCBs.There are several main reasons for choosing multilayer PCBs over single-layer PCBs:

1. Increased circuit density

Space utilization:

Multilayer PCBs are able to lay out more circuit alignments in a limited amount of space, allowing for more sophisticated designs, especially for small electronic devices such as smartphones and computers.

Complex design requirements:

Since multilayer PCBs enable more complex circuit layouts, they can meet the demands of modern electronics for versatility and high-speed signal transmission.

Improved Signal Integrity

Signal and Ground Layer Configuration:

Multilayer designs can create isolation between signal and ground layers, reducing signal interference and improving signal integrity and stability.

Reduced EMI:

Through reasonable layer arrangement, multi-layer PCBs can effectively reduce electromagnetic interference and improve the overall performance of the device.

Reducing Power Interference

Layered power management:

Multi-layer PCB design can place power and grounding at specific levels to reduce the crossing of power and signal lines and reduce the impact of power noise on signals.

Improved Current Handling:

Higher currents can be handled by increasing the thickness of copper layers, providing better power distribution and heat dissipation.

Simplifies fabrication and soldering processes

Reduces wiring complexity:

Multi-layer PCBs can reduce the number of wires used on the surface, so the soldering process can be simplified, making assembly less difficult and reducing potential errors.

Facilitates automated production:

In modern production, multi-layer PCBs are easier to adapt to automated production lines, increasing productivity.

Provides better thermal management

Optimized thermal performance:

The structural configuration of multi-layer PCBs allows heat to be dissipated more efficiently, resulting in improved reliability and durability of the equipment.

Temperature Control:

The rational layer design enables management of the temperature of different components, preventing failures due to overheating.

The efficiency of a PCB board depends on the number of layers, therefore, selecting the correct number of PCB board layers is crucial.