What is a PCB?
PCB (Printed Circuit Board), also known as a printed wiring board, is an indispensable core component in electronic systems. It forms conductive traces on an insulating substrate through a printing process, providing stable mechanical mounting support for various electronic components such as resistors, capacitors, and IC chips, while undertaking core tasks including electrical interconnection, signal transmission, and power delivery.
Because it is fabricated using electronic printing technology, it is called a "printed" circuit board. Since its inception, the PCB has been hailed as "The Mother of Electronic Products." Virtually all electronic devices—from small items like electronic watches and calculators to large systems like computers, communications equipment, and military weapons systems—require printed boards to achieve electrical interconnection wherever integrated circuits and other electronic components are present.
The emergence of PCBs completely transformed the electronics industry. Compared with traditional point-to-point wiring methods, PCBs dramatically simplified the assembly, soldering, and debugging of electronic products, reduced wiring workload, significantly shrunk product volume, lowered production costs, improved electronic device quality and reliability, and enabled large-scale, automated electronics manufacturing.
Evolution & History
Conceptual Origins & Technical Invention
In 1903, German inventor Albert Hanson pioneered the concept of using cut metal foil as circuit conductors in telephone exchange systems, proposing ideas for double-sided through-holes and multi-layer circuits. In 1936, Austrian engineer Paul Eisler developed the first printed circuit board for a radio using a subtractive process, earning him recognition as the "Father of Printed Circuits."
World War II Drives Commercialization
In 1943, the United States extensively used PCB technology in military radios and proximity fuzes. In 1948, the U.S. officially recognized printed circuit board inventions for commercial use. In the 1950s, the popularity of transistors shrunk electronic product sizes; in 1953, Motorola developed plated-through-hole (PTH) double-sided boards, and PCB technology began to be widely adopted.
Multi-Layer Boards & Automated Design
From the 1960s onward, multi-layer PCBs emerged and developed rapidly, progressing from 4 layers to 6, 8, 10, and beyond. In 1960, V. Dahlgreen invented the flexible printed circuit (FPC). Integrated circuits became widespread in the 1970s; in the 1980s, Surface Mount Technology (SMT) began replacing through-hole mounting, and computers with EDA software ushered PCB design into the digital era.
HDI & The Portable Device Revolution
The proliferation of personal computers and the internet drove PCBs toward miniaturization and high density. The emergence of smartphones in the early 21st century propelled the development of High-Density Interconnect (HDI) technology, with line width/space reaching the 40μm level and any-layer interconnect technology entering use. During this period, China absorbed global capacity transfers and became the world's largest PCB manufacturing base.
AI-Driven High-End Advancement
Demand for AI servers and high-speed optical modules has exploded, with PCB layer counts commonly rising to 20–30 layers or more. Advanced processes such as laser drilling and any-layer interconnect are widely applied. Global PCB output value is projected to surpass $100 billion in 2026, and the tight supply-demand balance for high-end PCBs may persist through 2028.
PCB Classification System
Single-Sided Board
Conductive copper foil on one side only, with components concentrated on the other side and traces appearing on a single side. The simplest structure at the lowest cost, but subject to strict routing constraints.
Double-Sided Board
Conductive patterns on both sides, connected by plated through vias (PTH). Doubled routing space enables more flexible designs, making this the most widely used general-purpose PCB type.
Multi-Layer Board
Three or more conductive layers stacked together, with dedicated power and ground planes in the inner layers; densely routed with excellent EMI resistance. AI server motherboards can reach 20–30+ layers.
Manufacturing Process Flow
PCB manufacturing is a systematic engineering discipline integrating precision processing and strict quality control, combining materials science, photochemistry, electrochemistry, precision machinery, and computer vision. A high-performance multi-layer PCB can require over a hundred production steps; from design to finished product typically takes 5–15 days, spanning more than 20 core process stages.
Inner Layer Patterning
After cutting copper-clad laminates (CCL) to size, inner layer traces are formed through photoresist coating, UV exposure, developing, etching, and resist stripping. Completed panels undergo AOI (Automated Optical Inspection) to detect opens and shorts, followed by brown oxidation to roughen copper surfaces and enhance interlayer adhesion.
Lamination
Inner layer cores, prepreg (PP), and outer copper foils are precisely stacked in the designed sequence and placed in a vacuum hot press, where they are bonded at temperatures above 180°C and pressures of 300 psi, causing the prepreg to melt and cure, fusing all materials into an integrated multi-layer board.
Drilling & Hole Metallization
Through holes, blind vias, and buried vias are drilled using CNC machines or lasers (laser via diameters on HDI boards can be less than 0.1mm). After drilling, deburring and desmear treatments are performed, followed by electroless copper deposition and panel plating to metallize hole walls and establish interlayer electrical connections.
Outer Layer Patterning
Pattern transfer is performed again—dry film lamination, exposure, and developing—followed by pattern plating to thicken trace copper and via copper; excess copper foil is etched away to form outer layer conductive patterns, after which AOI inspection is conducted once more.
Solder Mask & Surface Finish
Solder mask ink is applied (the familiar green color is the solder mask), then exposed and developed to expose pads. Surface finishes—HASL, ENIG, OSP, immersion silver, etc.—are then applied to protect pads from oxidation and ensure reliable solderability.
Silkscreen, Profiling & Testing
White silkscreen legends are printed to mark component reference designators and polarity. Boards are routed to final dimensions via CNC milling or V-cut scoring. Finally, flying probe or fixture testing is performed to verify all circuits for opens and shorts, ensuring electrical performance meets specifications.
Application Areas
The PCB industry plays a pivotal bridging role across the entire electronics supply chain, with extraordinarily broad downstream applications. In recent years, emerging fields such as AI computing, automotive electronics, and 5G communications have become the core drivers of PCB demand growth.
AI Computing
AI Servers, Accelerator Cards, High-Speed Switches, Optical Modules
Consumer Electronics
Smartphones, Laptops, Wearable Devices
Automotive Electronics
Autonomous Driving, BMS, Automotive Radar
Communications Equipment
5G Base Stations, Routers, Satellite Communications
Industrial Control
Industrial Motherboards, Robotics, Smart Manufacturing
Medical Devices
Patient Monitors, Ultrasound Equipment, Implantable Devices
Aerospace
Flight Control Systems, Satellite Payloads, Avionics
IoT
Smart Home, Sensors, Edge Computing Nodes
Global PCB Market Size Growth Trend
Future Trends
AI Computing Drives High-End Migration
AI server PCBs commonly reach 20–30+ layers, with per-rack value multiplying across platform generations. The global AI PCB market is projected to reach $41 billion by 2028, with the tight high-end supply-demand balance continuing through 2028.
High-Frequency High-Speed Material Upgrades
5G/6G communications and millimeter-wave radar are driving demand growth for low-Dk/Df high-speed materials such as PTFE, hydrocarbons, and M9-grade laminates. Domestic substitution of high-end copper-clad laminates is accelerating, with supply chain autonomy for core materials becoming an industry priority.
High Density & Advanced Packaging
Line width/space continues shrinking toward the 0.01mm level; any-layer interconnect, IC substrates, 3D integration, and other advanced packaging technologies are rapidly evolving. The boundary between PCBs and semiconductor packaging is blurring, enabling technologies such as Chiplet.
Smart Manufacturing & Green Initiatives
Industrial robots are accelerating penetration into PCB production lines, with automated loading/unloading, inspection, and process transfer enabling full automation. Halogen-free materials, eco-friendly processes, and energy conservation are becoming important directions for sustainable industry development.
"From a simple single-layer copper foil to 30+ layer high-rise boards carrying AI compute workloads, PCBs have witnessed 90 glorious years of the human electronics industry. Though hidden inside devices and unseen, they are truly the 'silent cornerstone' of the digital age."
— The Eternal Carrier of the Electronics Industry