Multilayer Circuit Board Wiring

High-frequency circuits require dense wiring and high integration. Using multi-layer boards is essential for effective wiring and reducing interference. When designing a PCB layout, choosing the right board size and number of layers is crucial. Intermediate layers can be utilized to create shields, implement grounding, and minimize parasitic inductance and signal transmission length. These measures enhance the reliability of high-frequency circuits by reducing signal cross-interference. Research shows that a four-layer board can have noise levels 20dB lower than a double-sided board made of the same material. However, increasing the number of layers can complicate manufacturing and raise costs. Thus, selecting the appropriate number of layers, careful component placement, and following wiring rules are vital for effective PCB design.

Minimize Lead Bends in High-Speed Electronic Devices

Straight leads are recommended for high-frequency circuit wiring. When turning is necessary, use a 45-degree corner or a circular arc to enhance mechanical strength and reduce external emissions and signal coupling in high-frequency circuits.

Minimize Lead Length Between Pins in High-Frequency Circuit Devices

Signal radiation intensity is proportional to trace length. To reduce coupling with nearby components, keep leads for high-frequency signals such as clock, crystal oscillator, DDR data, LVDS lines, USB lines, and HDMI lines as short as possible.

Reducing Vias in High-Frequency Circuit Devices

Minimize the number of vias between pins to improve performance. Each via introduces around 0.5pF of distributed capacitance, so reducing vias can boost speed and reduce data errors.

Minimizing Crosstalk in High-Frequency Circuits

Design high-frequency circuits with consideration for crosstalk from closely spaced parallel signal lines. To minimize crosstalk:

• Insert a ground wire or plane between signal lines
• Place a large ground area opposite parallel signal lines
• Increase spacing between signal lines
• Ensure perpendicular orientation of adjacent layers’ wiring
• Surround clock lines with ground lines in digital circuits
• Ground unused input terminals to reduce interference

High-Frequency Decoupling Capacitors

Add high-frequency decoupling capacitors near power supply pins of each integrated circuit block to suppress interference from high-frequency harmonics effectively.

Grounding Tips for PCB Design

• Separate ground wires for high-frequency digital and analog signals
• Use high-frequency choke magnetic beads for isolation
• Consider single-point interconnection for common ground
• Prevent interference by maintaining signal integrity

It is crucial to isolate the ground wires of high-frequency digital signals from analog signal ground wires in PCB design. When connecting these grounds to a common point, consider using high-frequency choke magnetic beads or direct isolation at a suitable location to avoid interference caused by inconsistent potentials and harmonic components. Ground coupling can lead to signal integrity issues, so proper isolation methods are essential.