What's the main point when PCB designer design high layer boards ?

When PCB designers design high-layer circuit boards, they will encounter the following difficulties:

I. Signal integrity issues

1. High-speed signal transmission - High-layer circuit boards often need to handle high-speed digital signals such as Gigabit Ethernet and PCI Express. During the transmission of these high-speed signals, they will be affected by reflection, crosstalk, attenuation, etc., resulting in signal distortion and an increase in bit error rate. - Designers need to reasonably plan signal traces and control parameters such as trace length, width, and spacing to reduce signal reflection and crosstalk. At the same time, appropriate termination technologies such as series resistors and parallel capacitors should be used to improve signal quality.

2. Power integrity - The power distribution network on high-layer circuit boards needs to provide stable power for various chips and circuits. However, due to changes in power current and the presence of distributed inductance, power voltage will fluctuate and generate noise, affecting the normal operation of circuits. - Designers need to reasonably design the layout of power layers and ground layers to reduce power impedance and improve power stability.

At the same time, technologies such as decoupling capacitors and power plane segmentation can be used to reduce power noise and interference.

II. Heat dissipation issues

1. Increased power density - The integration level of chips and circuits on high-layer circuit boards is getting higher and higher, and the power density is also increasing. This makes the heat dissipation problem more prominent. Excessive temperature will affect the performance and reliability of chips. - Designers need to reasonably plan the layout of the circuit board, disperse the chips with large heat generation, and avoid local overheating. At the same time, heat sinks, fans and other cooling measures can be used to reduce the temperature of the circuit board.

2. Thermal resistance and heat conduction - High-layer circuit boards have more layers, and the thermal resistance also increases accordingly. This makes it difficult for heat to dissipate quickly, and it is easy to cause local high temperatures. - Designers need to choose materials with good thermal conductivity, such as PCB boards with high thermal conductivity and heat dissipation pads, to improve the heat conduction efficiency.

At the same time, reasonable design of heat dissipation channels and the use of natural convection and forced air cooling can enhance the heat dissipation effect.

III. Electromagnetic compatibility issues

1. Radiation and anti-interference - High-speed digital signals and high-frequency analog signals on high-layer circuit boards will generate electromagnetic radiation and cause interference to surrounding electronic equipment. At the same time, the circuit board is also easily affected by external electromagnetic interference, resulting in degraded performance or failure. - Designers need to reasonably plan the layout of the circuit board, separate sensitive circuits and interference sources, and reduce electromagnetic radiation and interference. At the same time, electromagnetic compatibility measures such as shielding covers and filtering capacitors can be used to improve the anti-interference ability of the circuit board.

2. Grounding and shielding - Good grounding and shielding are the key to solving electromagnetic compatibility problems. However, the design of grounding and shielding layers for high-layer circuit boards becomes more complex due to the large number of layers. - Designers need to reasonably design the layout of grounding and shielding layers to ensure good grounding and effective shielding.

At the same time, attention should be paid to parameters such as grounding impedance and shielding effectiveness to meet electromagnetic compatibility requirements.

IV. Manufacturability issues

1. Lamination process - The lamination process of high-layer circuit boards has higher requirements and needs to ensure the bonding strength and electrical performance between layers. At the same time, defects such as bubbles and delamination are easy to occur during the lamination process, affecting the quality of the circuit board. - Designers need to work closely with PCB manufacturers to understand the requirements and limitations of the lamination process and reasonably design the layer structure and parameters of the circuit board. At the same time, strict quality control should be carried out to ensure the lamination quality of the circuit board.

2. Drilling and routing - Drilling and routing on high-layer circuit boards are more difficult and require the use of high-precision equipment and processes. At the same time, deviations and short circuits are easy to occur during drilling and routing, affecting the performance and reliability of the circuit board. - Designers need to reasonably plan the drilling and routing schemes and select appropriate parameters such as hole diameter, line width, and spacing.

At the same time, strict design rule checks and electrical performance tests should be carried out to ensure the drilling and routing quality of the circuit board. In short, when PCB designers design high-layer circuit boards, they need to comprehensively consider issues such as signal integrity, heat dissipation, electromagnetic compatibility, and manufacturability, and adopt reasonable design methods and technical measures to ensure the performance and reliability of the circuit board.