2-Layer PCB VS 4-Layer PCB: Advantages, Differences, and Processes

2-Layer PCB VS 4-Layer PCB: Advantages, Differences, and Processes

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The number of layers in a PCB can vary significantly, with higher-layer PCBs requiring more intricate designs and manufacturing processes. High-end products often opt for multilayer PCBs. For most electronic devices, single-layer, 2-layer, and 4-layer PCBs are commonly used. This article focuses on introducing the advantages, differences, and manufacturing processes of 2-layer and 4-layer PCBs to help you choose the right type for your project.

2-Layer PCBs

Let’s first explore the widely used 2-layer PCBs. Similar to standard plastic boards, 2-layer PCBs consist of a substrate, copper layers, pads, and printed markings.

  • The copper layers are on both sides of the board, with the substrate sandwiched in between.
  • Typically, the substrate thickness ranges from 0.8 mm to 1.6 mm.
  • An additional inorganic compound layer can be applied to the copper surfaces to enhance electrical and mechanical performance, if required.

The manufacturing process for 2-layer PCBs is relatively simple and cost-effective, making them affordable and easy to produce and repair. However, 2-layer PCBs have a significant limitation: they only provide two sides for routing. For complex circuits requiring extensive routing, a 4-layer PCB might be necessary.

4-Layer PCBs

Compared to 2-layer PCBs, 4-layer PCBs offer greater flexibility and reliability.

  • 4-layer PCBs typically include two additional inner layers.
  • By distributing circuit topology across four layers, 4-layer PCBs make routing more convenient and enable easier validation and adjustment when routing issues arise.
  • The extra copper layers in 4-layer PCBs also provide enhanced resistance to electromagnetic interference (EMI). Compared to 2-layer PCBs, their EMI performance is significantly superior.

However, manufacturing 4-layer PCBs requires more advanced machinery and skilled labor, resulting in higher costs. Consequently, 4-layer PCBs are more expensive than their 2-layer counterparts.

2-Layer PCB

Advantages of 2-Layer PCBs

  • Design Flexibility: 2-layer PCBs are relatively simple in design yet offer high flexibility, making them suitable for a wide range of devices. Their double-sided layout allows components to be arranged and connected on both sides, providing additional design space.
  • Cost-Effective Structure: With a simpler structure, 2-layer PCBs are less expensive to manufacture. This makes them highly cost-effective for mass production.
  • Compact Size: The smaller size of 2-layer PCBs contributes to reducing the overall size of products, making them well-suited for various compact devices.
  • Broad Application: 2-layer PCBs are widely used in both simple and moderately complex electronic devices, such as HVAC systems, amplifiers, and printers. These applications typically do not require extensive routing space or complex circuitry, making 2-layer PCBs an ideal choice.

Advantages of 4-Layer PCBs

  • Increased Routing Density: Compared to 2-layer PCBs, 4-layer PCBs provide additional routing space, enabling the integration of more electronic components. This improves the performance and integration level of the device.
  • Reduced Signal Interference: 4-layer PCBs support the use of ground and power planes, which help minimize signal interference and enhance signal integrity. Additionally, multilayer PCBs offer superior electromagnetic compatibility (EMC) and electromagnetic interference (EMI) control.
  • Improved Thermal Performance: With more layers, 4-layer PCBs can better dissipate heat, enhancing the system’s overall thermal performance. This is particularly important for high-power electronic devices, as excessive heat can degrade performance or even cause damage.
  • Wide Range of Applications: 4-layer PCBs are extensively used in electronic devices such as computers, communication equipment, and consumer electronics. These devices often demand higher integration, smaller sizes, and better EMI control, making 4-layer PCBs the preferred choice.

Differences Between Double-Sided PCBs and 4-Layer PCBs

Difference 1: Structure
A 4-layer PCB consists of two inner copper layers and two substrate layers, forming a more complex internal structure. In contrast, a double-sided PCB has only one substrate layer, with copper foils on both sides. This structural difference results in distinct design and manufacturing requirements.

Difference 2: Routing Capability
Compared to double-sided PCBs, 4-layer PCBs provide additional internal layers for routing. This gives them advantages in high-speed signal transmission and impedance control, enabling more complex circuit layouts. Double-sided PCBs have limited routing space, making them more suitable for simple circuit designs and low-speed signal transmission.

Difference 3: Electromagnetic Shielding
With internal layers, 4-layer PCBs offer superior electromagnetic shielding. This makes them a preferred choice for applications sensitive to electromagnetic interference (EMI), such as wireless communication devices. Double-sided PCBs, lacking internal layers, have weaker shielding capabilities.

Difference 4: Thermal Management
4-layer PCBs outperform double-sided PCBs in heat dissipation. The additional substrate layer increases the board’s thickness, enhancing thermal performance. This makes 4-layer PCBs more suitable for applications with high heat dissipation requirements, such as LED lighting.

Difference 5: Cost and Complexity
Due to their more complex structure and higher manufacturing demands, 4-layer PCBs are more expensive to produce. Additionally, their design and manufacturing processes are relatively intricate, which may be excessive for simple applications. Double-sided PCBs, being simpler and more cost-effective, are ideal for applications with lower requirements for cost and complexity.

4-Layer PCBs

Manufacturing Process of 2-Layer PCBs

The production process for 2-layer PCBs is relatively straightforward and can be divided into five main steps:

  1. Circuit Design: Design the circuit schematic and routing diagram according to project requirements.
  2. Printing: Transfer the designed circuit pattern onto a film and use it to create the PCB printing template.
  3. Chemical Etching: Place the PCB in a chemical solution to etch away excess copper foil through chemical reactions.
  4. Drilling: Use automated machinery to drill holes for electrical components to be inserted into the PCB.
  5. Surface Treatment: Coat the PCB surface with a layer of tin to prevent oxidation and facilitate subsequent processes like soldering.

Manufacturing Process of 4-Layer PCBs

The production of 4-layer PCBs is more complex, involving the following steps:

  1. Inner Layer Board Fabrication: Punch holes and apply film to a copper sheet, then laminate it with a copper-clad sheet to form the inner layer circuit board.
  2. Outer Layer Printing: Print the circuit pattern on the surface and use etching or similar methods to create the desired conductive pathways.
  3. Pad Processing: Reserve space along the edges of the 4-layer PCB for component soldering.
  4. Layered Drilling: Use drilling machines to create holes in both the inner and outer layers as required.
  5. Passivation Treatment: Immerse the PCB in a chemical solution to prepare the pads for soldering and prevent damage from tin.
  6. Copper Plating: Apply silver or copper foil to the PCB surface and perform chemical etching and other processing steps.

In summary, 2-layer PCBs, with their simple structure and low cost, are ideal for consumer electronics, communication devices, and applications with modest routing requirements. On the other hand, 4-layer PCBs offer higher routing density, better signal integrity, and superior thermal performance, making them suitable for high-performance and reliability-critical applications like computer hardware, automotive electronics, and medical devices.