The difference between high-speed PCB and low-speed PCB

The main differences between high-speed PCB and low-speed PCB are signal transmission speed and frequency range and design complexity.

High-speed PCB is used to transmit high-frequency signals, whose frequency range is usually between hundreds of megahertz and tens of gigahertz.

The design complexity is high, and signal integrity and anti-interference ability need to be considered; while low-speed PCB is mainly used to process relatively high-frequency signals.

For low-frequency signals, the frequency range is usually between megahertz and tens of gigahertz, and the design is relatively simple.

Signal transmission speed

High-speed PCB refers to PCB with signal transmission rate exceeding 100MHz, while low-speed PCB refers to PCB with signal transmission rate lower than 100MHz. High-speed PCBs are usually used in high-speed digital circuits, radio frequency circuits and microwave circuits, while low-speed PCBs are used in analog circuits, low-speed digital circuits and power supply circuits.

Design

High-speed PCB needs to consider issues such as signal integrity (SI) and electromagnetic compatibility (EMC) when designing, so it requires more complex design methods and techniques. For example, high-speed PCB requires impedance matching, differential signal routing, high-speed signal simulation, etc. Low-speed PCBs have relatively low requirements for SI and EMC, and the design is relatively simple.

High Speed ​​PCB Design

  • Impedance matching

Impedance matching refers to matching the impedance of the PCB trace with the impedance of the signal source and load to reduce signal reflection and loss. High-speed PCBs require impedance matching to ensure signal integrity.

  • Differential Signal Routing

Differential signaling means that two signal lines transmit signals in opposite directions at the same time. Differential signal wiring can improve the common mode rejection ratio (CMRR) of the signal and reduce EMI interference. High-speed PCBs often use differential signal routing to improve signal transmission quality.

  • High speed signal simulation

High-speed signal simulation refers to using simulation software to simulate the transmission process of high-speed signals on PCB. High-speed signal simulation can help designers analyze signal integrity problems and find solutions.

Low Speed ​​PCB Design

Low-speed PCB has relatively low requirements for SI and EMC, so the design is relatively simple. Low-speed PCB design usually only needs to consider the following aspects:

  • Wiring rules: for example, minimum line width, minimum spacing, minimum bending radius, etc.
  • Component placement: For example, avoid placing them near heat sources, avoid placing them at intersections of signal lines, etc.
    *Laminated structure: For example, the design of power and ground layers.

Manufacture

High-speed PCB has higher requirements on the manufacturing process and requires higher precision and control to ensure the flatness of the PCB board, the accuracy of the pads and the accuracy of the fine structure. For example, high-speed PCBs often require the use of higher-precision drilling and exposure machines and the use of stricter quality control standards. Low-speed PCB has relatively low requirements for manufacturing processes.

High Speed ​​PCB Manufacturing

  • material selection

High-speed PCBs require the use of materials with lower losses and higher dielectric constants to improve signal transmission performance. For example, high-speed PCBs often use high-Tg FR-4 materials or ceramic substrates.

  • Laminated structure

The stack-up structure of high-speed PCBs needs to be carefully designed to reduce signal loss and crosstalk. For example, high-speed PCBs often use multi-layer structures and use copper clad layers as ground planes.

  • Manufacturing Process

The manufacturing process of high-speed PCB needs to be more stringent to ensure the accuracy and quality of PCB. For example, high-speed PCBs often require the use of higher-precision drilling and exposure machines and the use of stricter quality control standards.

Low Speed ​​PCB Manufacturing

Low-speed PCB has relatively low requirements for material selection and manufacturing processes, and ordinary FR-4 materials and standard manufacturing processes can be used.

Material selection

High-speed PCBs require the use of materials with lower losses and higher dielectric constants to improve signal transmission performance. For example, high-speed PCBs often use high-Tg FR-4 materials or ceramic substrates. Low-speed PCBs can use ordinary FR-4 materials or other low-cost materials.

High Speed ​​PCB Material

  • PCB board

High-speed PCBs usually use high-Tg FR-4 materials or ceramic substrates. High Tg value materials have lower losses and higher dielectric constants, which can improve signal transmission performance.

  • Copper clad layer

High-speed PCBs typically use thicker copper layers to reduce signal loss and improve heat dissipation.

  • Dielectric Materials

High-speed PCBs often use dielectric materials with low losses to reduce signal loss.

Low Speed ​​PCB Material

Low-speed PCBs can use ordinary FR-4 materials or other low-cost materials.

Cost

Because high-speed PCBs have higher requirements in terms of design, manufacturing, and material selection, their costs are usually higher than low-speed PCBs.

Application

High-speed PCB and low-speed PCB are used in different fields.

High Speed ​​PCB Applications

  • High-speed digital circuits: for example, computer motherboards, communication equipment, storage devices, etc.
  • Radio frequency circuits: for example, wireless communication equipment, radar, navigation equipment, etc.
    *Microwave circuits: For example, microwave ovens, radars, communication equipment, etc.

Low speed PCB applications

Analog circuits: For example, power circuits, amplifier circuits, filter circuits, etc.
Low-speed digital circuits: for example, control circuits, display circuits, keyboard circuits, etc.
Power circuit: For example, motor control circuit, power supply circuit, LED drive circuit, etc.

Summarize

High-speed PCB and low-speed PCB are two different PCB types, which differ in signal transmission speed, design, manufacturing, material selection and cost. When selecting a PCB type, comprehensive considerations need to be made based on application requirements.

Fumax focuses on electronic assembly services, providing OEM and OEM services to users around the world. Our PCB assembly factory is located in Shenzhen, China.

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