As an engineer at SuperPCBA, I am excited to present to you this article on the layering of multilayer circuit boards. In the modern electronics field, the use of multilayer circuit boards has become an integral part of complex electronic product design. For these multilayer circuit boards, understanding their layering and the rational design of layers is not only the foundation for achieving circuit functionality but also a crucial aspect in ensuring product performance and reliability.

In this article, we will delve into the necessity of layering in multilayer circuit boards, introduce the functions of different layers, and discuss how to design more rational and efficient layering schemes to meet the complexity requirements of various electronic products for circuit boards.

The Significance of Layered Design in Circuit Boards

In order to achieve electrical performance, feasibility, and maintainability of circuit boards, a layered design is essential. Layering in circuit boards involves dividing the design into distinct levels, each serving unique functions and tasks. A typical multilayer circuit board comprises inner and outer layers, each with specific functionalities.

The inner layers typically constitute the intermediate layers of the circuit board, sandwiched between two outer layers. These inner layers establish electrical connections with the outer layers through vias, facilitating communication with external components and other layers. This includes signal layers, power layers, ground layers, among others.

The outer layers represent the visible surface layers of the circuit board, featuring silk screen layers, solder mask layers, and copper layers.

Now, let’s delve into a detailed understanding of these distinct circuit board layers.

Distinct Circuit Board Layers

When designing multilayer circuit boards, it’s common to distribute components and conductors of different functions across various layers to optimize performance and layout. Here are some common circuit board layers and their functions:

1: Inner Layers:

Signal Layer:

• Function: Primarily used for transmitting signals within electronic devices, including data lines and control lines.
• Design Considerations: Layout of the signal layer needs to consider signal integrity, impedance matching, and other factors.

Power Plane:

• Function: Provides power to electronic components. The power plane is typically filled with copper to create a low-impedance path for current.
• Design Considerations: Layout of the power plane needs to consider current distribution, voltage stability, and other factors.

Ground Plane:

• Function: Provides the ground (reference) connection for the circuit. The ground plane helps reduce interference between signal pins, enhancing the circuit’s overall immunity to interference.
• Design Considerations: Well-designed ground planes are crucial for maintaining signal integrity and reducing electromagnetic interference.

2: Outer Layers:

Solder Mask Layer:

• Function: Insulating material covering wires and solder pads to prevent short circuits and protect conductors.
• Design Considerations: The solder mask layer typically includes some openings to allow solder connections.

Silkscreen Layer:

• Function: Provides identification for components on the circuit board, including reference marks, component values, company logos, etc.
• Design Considerations: Information on the silkscreen layer should be clear and legible without affecting the normal functionality of components.

Solder Resist Layer:

• Function: Used to cover areas where soldering is not required, preventing short circuits and protecting the circuit board surface.
• Design Considerations: Openings in the solder resist layer should correspond to the positions of solder pads for soldering.

The design of these layers needs to be optimized based on specific applications and performance requirements. Well-crafted circuit board layouts and layering designs can enhance circuit performance, reliability, and manufacturing efficiency.

How to Thoughtfully Plan the Layering of Circuit Boards

A well-executed design for circuit board layering should adhere to a set of standards and best practices to ensure the circuit’s performance, reliability, and manufacturability. Here are some common standards and guidelines:

Signal Integrity:

• Impedance Matching: Ensure impedance matching for transmission lines on signal layers to prevent signal reflections and waveform distortion.
• Differential Pairs: Maintain proximity for differential pairs to reduce electromagnetic interference.

Power and Ground Layer Design:

• Low Impedance Paths: Power and ground layers should provide low-impedance paths to ensure a stable power supply and reduce voltage drop along signal return paths.
• Distributed Capacitance: Introduce distributed capacitance between power and ground layers to facilitate stable power filtering.

Thermal Management:

• Heat Dissipation Paths: Ensure heat dissipation paths on the circuit board, especially for high-power components, to prevent overheating.
• Fans and Heat Sinks: Allocate adequate space in the design for fans or heat sinks to enhance heat dissipation.

EMI and RFI Suppression:

• Ground Layer Planning: Use well-designed ground layers to minimize electromagnetic interference.
• Differential Pair Layout: Arrange differential pairs and use differential signaling to reduce sensitivity to electromagnetic interference.

Manufacturability:

• Layer Alignment: Ensure accurate alignment between inner and outer layers to prevent connectivity issues during manufacturing.
• Minimum Hole Size and Trace Width/Spacing: Choose appropriate hole sizes and trace width/spacing considering manufacturing capabilities and cost.

Testing and Maintainability:

• Test Point Layout: Design test points at critical locations for easy testing and troubleshooting of the circuit board.
• Component Labeling: Provide clear component labeling on the silkscreen layer for ease of maintenance and repair.

Environmental Requirements:

• RoHS Compliance: Adhere to environmental requirements such as the Restriction of Hazardous Substances (RoHS) directive.
• Energy Consumption Optimization: Design with energy consumption in mind, optimizing power usage wherever possible.

IPC Standards:

• Compliance with IPC Standards: Adhere to relevant circuit board design and manufacturing standards published by the Association Connecting Electronics Industries (IPC) for industry recognition and compliance.

These standards and best practices aim to ensure the performance, manufacturability, and maintainability of circuit boards. During the design process, adjustments to these guidelines may be necessary based on different applications and requirements. The ultimate success of the design heavily relies on the experience of the design team and a profound understanding of the specific application.

Conclusion

By delving into the intricacies of multilayer circuit board layering, we aim to enhance your grasp of the core elements in electronic product design. SuperPCBA, guided by a commitment to innovation and excellence, continually elevates its technological prowess in the realm of multilayer circuit board manufacturing, delivering top-tier electronic solutions to our clients.

Should you have any inquiries or collaboration needs in multilayer circuit board layering design or other related fields, we warmly welcome you to reach out at any time. The SuperPCBA team is dedicated to providing you with professional consulting services, tailoring optimal electronic manufacturing solutions for your unique requirements. Let us collaborate to shape the future and infuse your electronic products with even greater innovation!