IBE enables the world’s best brands. Through our unrivalled customer-centric approach, we partner with leading companies in numerous markets to deliver solutions for their most complex challenges.

Gallery
Contacts

IBe Industry Building, ShenZhen, China

ibe@ibepcbaaa.com

+86-75581785031

PCB/PCBA knowledge
Graphics | Explanation of Single, 2, 4, 6, 8, 10, and 12-Layer PCB

The number of layers in a printed circuit board, simply put, refers to the number of independent conductive layers that make up the board. Each layer consists of insulation material (such as FR-4 fiberglass board) and copper foil, with predefined circuit patterns etched onto the copper foil. These conductive layers are interconnected through vias or buried vias, forming complex electrical networks.

Common layer counts for circuit boards include single layer boards, double layer boards, four layer boards, six layer boards, eight layer boards, and even higher layer multilayer boards. More layers mean that more complex circuits can be arranged in a limited space, enhancing device integration and performance, but it also increases manufacturing difficulty and cost.

Table of Contents

PCB layers

A multilayer PCB board is a type of printed circuit board with multiple internal layers, achieving the combination and integration of various functional modules by establishing electrical connections between different internal layers. Its structural composition mainly includes the following parts:

1. Signal Layer: The signal layer is the core part of a multilayer PCB board, 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, etc.

2. Power Layer: The power layer is mainly responsible for providing stable DC power to various functional modules. Depending on the requirements, the power layer can be divided into +Vcc (positive power), -Vcc (negative power), +GND (ground), and -GND (ground), etc. The layout and design of the power layer are crucial for the overall circuit performance.

3. Ground Layer: The ground layer is used to connect the common ground between various functional modules to achieve good electromagnetic compatibility (EMC). The material and layout of the ground layer play an important role in reducing interference noise and improving system stability. Common ground layer materials include FR-4, Rogers, etc.

4. Top and Bottom Layers: The top and bottom layers are located respectively on the outermost and innermost layers of the multilayer PCB board, usually used to install fixed metal contacts such as sockets, plugs, antennas, etc. In addition, the top layer can also be used to install panel indicator lights, buttons, and other auxiliary components.

Single Layer Board

A single layer board is the most basic type of PCB, also known as a single-sided board, because conductors only appear on one side. Therefore, we call this type of PCB a single-sided board.

Single Layer Boards are commonly used in simple electronic devices with uncomplicated circuitry.

The structure of a multilayer board consists of multiple layers of circuit boards, each layer stacked and connected in a certain way to form a whole. A multilayer board can be divided into four main components:

– Inner Layer Circuit Board: The circuit board inside the multilayer board, typically an even number of layers, can be a double-sided board or a multilayer board.

– Outer Layer Circuit Board: The surface circuit board of the multilayer board, typically a double-sided board or a multilayer board.

– Dielectric Layer: The dielectric layer inside the multilayer board, typically made of polymer materials or glass fiber.

– Conductive Layer: The conductive layer inside the multilayer board, typically made of metal materials such as copper foil or aluminum foil.

Double-Layer Board

The board we usually create is a two-layer board, also known as a double-sided board, meaning that wiring can be done on both sides of the board. When we prohibit wiring on one side, it becomes a single layer board again.

2-Layer PCBs are widely used in various electronic devices, including consumer electronics, industrial equipment, and automotive applications.

4-Layer Board

A four-layer board uses two double-layer PCBs with an insulating layer placed between the two layers.

These boards offer enhanced routing capabilities and reduced signal interference compared to 2-Layer PCBs. They are commonly used in applications where higher circuit density and better signal integrity are required, such as communication devices, medical equipment, and aerospace systems.

6-Layer Board

A six-layer board consists of one four-layer PCB with an additional single-layer board on top and bottom. The design advantage of a six-layer board is that it can optimize electromagnetic interference and transmit signals at different speeds.

6-Layer PCBs are often utilized in high-speed digital and analog circuits, as well as in advanced computing systems and network infrastructure.

8-Layer Board

An eight-layer board is understood similarly to a six-layer board, with an additional single-layer board added on top and bottom of a six-layer board. Typically, there are four routing layers and four reference plane layers, providing the best signal integrity and EMC characteristics.

8-Layer PCBs are commonly employed in complex electronic systems, including high-frequency RF (Radio Frequency) devices, advanced computer motherboards, and high-performance industrial control systems.

10 and 12-Layer Board

Ten-layer boards, as well as 12-layer boards and higher, are mostly used in smartphones, data server boards, and are mostly flexible boards.

A 10-Layer PCB consists of ten layers of conductive material with insulating layers between them. These boards are utilized in applications requiring extremely dense circuitry, high-speed signal transmission, and stringent electromagnetic compatibility (EMC) requirements. 10-Layer PCBs are frequently found in telecommunications equipment, data storage devices, and sophisticated test and measurement instruments.

A 12-Layer PCB comprises twelve layers of conductive material alternated with insulating layers. These boards provide the highest level of design flexibility, allowing for complex multilayered circuit layouts and advanced signal routing.
12-Layer PCBs are extensively used in cutting-edge electronic products, such as high-end smartphones, networking infrastructure, and advanced medical devices, where optimal performance and reliability are paramount.

The Role and Impact of the Number of Layers in a PCB

Increase Integration: Multilayer circuit boards can distribute circuits of different functions across different layers, allowing electronic devices to accommodate more components in limited space, thus increasing device integration.

Optimize Signal Quality: For high-speed, high-precision electronic systems, multilayer boards can effectively isolate different types of signals by setting up dedicated power layers, ground layers, and signal layers, reducing interference and improving the quality and stability of signal transmission.

Reduce Electromagnetic Interference (EMI): Multilayer boards can effectively suppress electromagnetic radiation through reasonable layout and grounding design, meeting electromagnetic compatibility (EMC) requirements.

Impact on Cost and Manufacturing Process: As the number of layers increases, the manufacturing cost of the circuit board, the complexity of the process, and the requirements for production equipment also increase. The design and production processes require more precise alignment technology, stricter interlayer insulation control, and more advanced detection methods.

How to Identify the Number of Layers in a Circuit Board

Identifying the number of layers in a circuit board typically requires a combination of visual observation, physical measurements, and professional equipment testing:

Visual Observation: For simple single-layer or double-layer boards, the wiring situation on both sides of the board can be observed directly with the naked eye. If both sides have wiring and no obvious vias are visible, it is generally a double-layer board; if only one side has wiring, it is a single-layer board. For multilayer boards, since the internal conductive layers are wrapped in insulation material and difficult to observe directly, other methods need to be used for judgment.

Physical Measurements: By measuring the thickness of the circuit board and combining it with standard values ​​for common circuit board materials and copper foil thicknesses, the possible number of layers can be roughly estimated. For example, if the thickness of a certain circuit board is measured to be about 1.6mm, considering that common FR-4 material is about 0.17mm per layer, plus two copper foils on both sides are about 0.035mm each, it can be inferred that the board may be 4 layers or 6 layers. However, this is only a rough estimate, and the actual number of layers needs further confirmation.

Professional Equipment Testing: The most accurate method is to use professional equipment such as X-ray fluoroscopy or scanning sonar for testing. X-ray fluoroscopy can penetrate insulation materials and clearly display the distribution of internal conductive layers, while scanning sonar uses ultrasound to detect the interlayer distance and structure of the circuit board, accurately determining the number of layers. These methods are suitable for situations where the number of layers in the circuit board is strictly required, such as product quality inspection, fault analysis, etc.

In summary, the number of layers in a circuit board is an important parameter of its structural characteristics, directly affecting device integration, performance, and manufacturing cost. By observing appearance, making physical measurements, and using professional equipment, we can effectively identify the number of layers in a circuit board. Understanding and mastering this knowledge not only helps us better understand the internal structure of electronic devices but also helps us make wiser decisions in designing, purchasing, or repairing electronic devices.

FAQ

A Single Layer Board, also known as a single-sided board, is the simplest type of PCB (Printed Circuit Board) that contains conductive material on only one side. Components are mounted on one side of the board, and the conductive traces are on the opposite side. Single Layer Boards are commonly used in simple electronic devices with uncomplicated circuitry.

A 2-Layer PCB, also known as a double-sided board, contains conductive material on both sides of the board. Components can be mounted and connected on both the top and bottom layers, allowing for more complex circuit designs compared to Single Layer Boards. 2-Layer PCBs are widely used in various electronic devices, including consumer electronics, industrial equipment, and automotive applications.

A 4-Layer PCB consists of four layers of conductive material separated by insulating layers (dielectric material). These boards offer enhanced routing capabilities and reduced signal interference compared to 2-Layer PCBs. They are commonly used in applications where higher circuit density and better signal integrity are required, such as communication devices, medical equipment, and aerospace systems.

Leave a comment

Your email address will not be published. Required fields are marked *