Comprehensive Analysis and Prospect of High-Precision and High-Layer PCB Technology

Comprehensive Analysis and Prospect of High-Precision and High-Layer PCB Technology

In the current era of rapid advancement of electronic technology, electronic products are constantly evolving towards being smaller, high-performance, and multifunctional. High-precision and high-layer printed circuit boards (PCBs) have thus become the crucial "cornerstone" of electronic equipment, shouldering the responsibility of complex circuit connection and signal transmission. This article delves deep into its structure, design, and manufacturing process, explores its wide range of applications, faces up to the challenges, and looks ahead to the trends.

I. Introduction

With the rapid development of modern electronic technology, being small, high-performance, and multifunctional has become the "standard configuration" of electronic products. In this trend, high-precision and high-layer PCBs stand out and are deeply integrated with electronic equipment, taking on the increasingly complex tasks of circuit and signal transmission. With the advantage of ultra-high-density integration, it not only meets the requirements of high-speed and high-frequency signal transmission but also provides a continuous driving force for technological iteration in the high-end electronics field with its good heat dissipation and reliability.

II. Structural Characteristics

1. Multilayer Board Stacking Structure

High-layer PCBs usually have more than 10 layers, and the stacking design is a key part. The ground layer and power layer are arranged alternately to build a shielding "fortress" and provide a stable current supply, reducing electromagnetic interference. The signal layers are carefully arranged according to signal characteristics to avoid crosstalk. High-speed communication PCBs often adopt the "signal - ground - signal - power - ground - signal..." pattern, with precise parameter adjustment to ensure smooth transmission.

2. Microvia and Blind/Buried Via Technology

Microvias and blind/buried vias are essential tools for high-density connection. Microvias can be as thin as dozens of micrometers, significantly increasing the wiring density. Blind vias connect the surface layer and the inner layer, while buried vias connect the inner layers. Both shorten the signal path, reducing delay and reflection. The mainboard of a smart phone uses them to ensure efficient and stable signal transmission of key components, meeting the high-speed communication needs of the phone.

3. High-Precision Circuit and Line Width/Spacing Control

The circuit precision of high-precision PCBs is maximized, with strict control of line width and spacing. The skin effect becomes prominent at high frequencies, and the line width is adjusted to dozens to hundreds of micrometers according to the frequency, with a similar line spacing to prevent signal loss and crosstalk. For high-speed computer PCBs encountering signals above 10 GHz, the line width is set to 50 - 80 μm, and the line spacing is 60 - 90 μm to ensure signal integrity and system stability.

III. Design Key Points

1．Signal Integrity Design

(1) Impedance Matching: Matching the characteristic impedance is crucial for the smooth transmission of signals and is related to the circuit geometry and dielectric constant. When transmitting high-speed differential signals, strict control of the differential pair's line width, line spacing, and distance from the ground layer is required to ensure compliance with the differential impedance and prevent signal distortion.

(2) Signal Layer Planning: Reasonable layout of signal layers is an effective way to prevent crosstalk. High-speed and low-speed signals are separated into different layers, and the wiring of adjacent layers is orthogonal to reduce coupling. In multilayer communication PCBs, radio frequency and digital signal layers are placed on different layer positions with added shielding to ensure signal independence and stability.

(3) Timing Analysis and Adjustment: High-precision PCBs have strict timing requirements, especially in high-speed digital circuits. Analyze and adjust the transmission delay, setup, and hold times carefully. Adjust the line length, add delay lines, or use clock chips to ensure that signals arrive on time and prevent data errors.

2．Power Integrity Design

(1) Power Layer and Ground Layer Planning: The power layer and ground layer are placed adjacent to each other to build a low-impedance power distribution network, providing a stable power supply and reducing noise. Server motherboards set multiple power layers according to the power requirements of components and connect them with vias to ensure an even power distribution.

(2) Decoupling Capacitor Layout: Decoupling capacitors are essential for purifying the power supply. Capacitors with different capacitance values are placed beside chips. Small-capacitance capacitors filter high frequencies, and large-capacitance capacitors stabilize the voltage. Smart phone PCBs densely place capacitors near chip pins to provide a clean power supply and improve anti-interference ability.

3．Heat Dissipation Design

(1) Heat Dissipation Layer and Heat Dissipation Vias: High-layer PCBs face great pressure for heat dissipation and usually are equipped with a metal heat dissipation layer and heat dissipation vias for heat conduction. Optimize the number, diameter, and distribution of vias according to the layout and power of heating elements to promote heat dissipation. The PCB of a power amplifier places a large number of vias around the chip and connects them to an aluminum base layer to quickly dissipate heat.

(2) Component Layout Optimization: Reasonable layout of components is also an effective measure for heat dissipation. Disperse heat-generating components, leave space for heat dissipation, and ensure smooth air circulation. Computer motherboards separate the CPU and Northbridge chips, reserve space, and equip heat dissipation devices to reduce the motherboard temperature and improve system stability.

IV. Manufacturing Process Challenges 

1．Lamination Process

The lamination process is full of difficulties. The large number of layers leads to high alignment precision requirements. Differences in the thermal expansion coefficients of materials cause stress, easily resulting in warping and delamination. Vacuum lamination is used in high-end PCB manufacturing to control temperature, pressure, and time, select matching materials, and improve the binding force between layers.

2．Microvia Processing and Electroplating

Microvia processing is crucial. Traditional drilling methods can hardly meet the requirements, while laser drilling has problems such as rough hole walls and residues, affecting electroplating. To ensure uniform plating in microvias, adjust the composition, temperature, and current density of the electroplating solution, use special methods such as pulse and jet electroplating, and add additives to improve the plating quality.

3．Circuit Etching and Surface Treatment

Circuit etching requires high precision and consistency. Control the parameters of the etching solution to prevent uneven etching of inner layer circuits. The surface treatment method is selected according to the application. High-frequency communication PCBs often use electroplated nickel-gold, while consumer electronics mostly use Organic Solderability Protectant (OSP).

V. Application Areas

1．Communication Equipment

The communication field is the main battlefield of high-precision and high-layer PCBs, with applications in base stations, terminals, and switching equipment. The Massive MIMO antenna of a 5G base station relies on it to precisely control signals, and the mainboard of a smart phone integrates multiple functions with its help, enabling high-speed networks, high-definition videos, and smooth games.

2．Computer

The computer field has a high demand for it. High-performance server, workstation motherboards, and high-end graphics cards rely on this technology. Server motherboards use it to connect multiple CPUs, memory, and PCIe slots, ensuring stable signal transmission and even power distribution; high-end graphics cards integrate GPU and other components to improve graphic processing ability.

3．Automotive Electronics

The intelligent and electrified development of automobiles has given rise to complex electronic systems, and high-layer PCBs play an important role. Engine control precisely adjusts parameters, the Battery Management System (BMS) of an electric vehicle monitors the battery, and the autonomous driving assistance system processes signals, improving the intelligence and safety of automobiles.

4．Aerospace

Aerospace has strict requirements for the reliability and miniaturization of electronic equipment, and high-layer PCBs bear an important responsibility. The avionics system of an aircraft integrates complex components, and satellite electronic equipment is highly integrated within a limited space to ensure the smooth progress of flight and space missions.

VI. Challenges and Development Trends

1．Challenges

(1) Cost Pressure: The manufacturing process is complex, and materials are expensive, resulting in high costs, which restricts its application in cost-sensitive fields such as consumer electronics. Enterprises often have to balance cost and performance.

(2) Breakthrough of Technical Bottlenecks: As the number of layers increases and the precision rises, problems such as microvia processing, interlayer alignment, and heat dissipation remain to be solved. Theories of signal and power integrity and electromagnetic compatibility also face challenges.

(3) Environmental Protection Requirements: PCB manufacturing involves a large number of chemicals, polluting the environment, and strict control of emissions has become a new challenge for the industry.

2．Development Trends

(1) Material Innovation and Optimization: Research and develop new materials to reduce the dielectric constant, improve thermal conductivity, and modify conductivity, and optimize combinations to meet special needs.

(2) Intelligent and Automated Manufacturing Process: With the help of AI, big data, and robotics technology, intelligently monitor and automatically adjust the manufacturing process to improve efficiency, reduce errors, and enhance quality.

(3) Integration and Development with Emerging Technologies: Integrate with flexible electronics, 3D printing, quantum computing, etc., to expand applications, trigger innovation, and initiate an electronic technology revolution.

VII. Conclusion

High-precision and high-layer PCB technology is the "pillar" of the electronics field. Although it currently faces challenges in terms of cost, technology, and environmental protection, with material and process innovations and technology integration, it will surely break through limitations, lay a solid foundation for the development of electronic equipment towards being smaller, high-performance, multifunctional, and highly reliable, and boost the electronics industry to new heights.