Anyone engaged in electronics projects, hardware development or MCU development inevitably works with PCBs. Inside smartphones, computers, earphones, home appliances and smart devices, the colorful board covered with traces, solder joints and electronic components is the Printed Circuit Board, or PCB. Serving as the core carrier of all electronic equipment, it mounts electronic components and transmits electrical power and signals, acting as the skeleton and vascular network of all hardware systems.

Prepared by Shenzhen Juehui Weiye Circuit Co., Ltd., this article is tailored for absolute beginners. Avoiding obscure jargon, it explains core PCB concepts, structural classifications, design workflows and beginner tips step by step, helping you build a comprehensive knowledge framework of PCBs rapidly.

1. What Is a PCB?

PCB stands for Printed Circuit Board. It is a standardized circuit board built on an insulating substrate. Copper traces and pads are formed via etching, electroplating and other processes to interconnect various electronic components following predefined circuit logic.

Before the wide adoption of PCBs, electronic circuits relied on hand-soldered flying wires. Such wiring was messy, prone to short circuits, high in failure rate and impossible for mass production. PCBs predefine and embed complex traces onto the board, solving all pain points of traditional wiring. They feature five major strengths: neat circuit routing, stable performance, compact size, support for mass manufacturing and convenient maintenance, laying the foundation for the rapid growth of the modern electronics industry.

Simply put, PCBs have two core functions. First, mechanical fixation: securely mount resistors, capacitors, chips, connectors and all other electronic components. Second, electrical interconnection: transmit electric current and signals through copper traces to enable the predefined functions of the circuit.

2. Core PCB Structure: Understand Every Layer of the Circuit Board

Newbies only notice the colored surface and silver solder joints on PCBs. In fact, conventional PCBs adopt a multi-layer composite structure, with each layer assigned unique functions. Mastering the structure marks your real start into PCB learning. General-purpose PCBs consist of 5 key components:

(1) Substrate

It forms the mechanical skeleton of a PCB, most commonly made of FR-4 insulating material. FR-4 features high rigidity, excellent insulation and thermal resistance. It supports the whole circuit board and isolates different traces to prevent leakage and short circuits. FR-4 is widely used for PCBs in consumer electronics and industrial equipment, while special substrates are adopted for high-end aerospace and medical devices.

(2) Copper Traces

Known as the "vessels" of the PCB, these thin copper lines remain after etching — the thin silver lines visible to the naked eye. Electric current and signals are transmitted through copper traces. The width, thickness and length of traces directly determine current-carrying capacity and signal stability.

(3) Pads

Dedicated soldering landing zones for electronic components, consisting of enlarged copper regions designed to secure component leads. During soldering, component leads are aligned on pads and fixed by solder to establish electrical connection between components and traces. Common pad shapes include round, square and rectangular types, matching components with different packages.

(4) Solder Mask

This is the protective green, blue, black or red coating on PCB surfaces, with green being the most prevalent. It covers all unused copper foil and board surface while exposing only pads. Its core functions include preventing copper oxidation, avoiding circuit short circuits, providing insulation and moisture resistance, resisting high temperature, and protecting traces against physical abrasion. Solder mask colors are purely aesthetic; there is no fundamental difference in performance.

(5) Silkscreen

The white printed texts, symbols, outlines and reference designators on PCBs, such as R1, C2, LED, GND and 5V. Silkscreen carries no electrical functions and serves purely for marking. It helps developers identify component models, pin definitions and circuit nodes, greatly lowering the difficulty of soldering, debugging and maintenance.

Auxiliary Structure: Vias

An essential feature for multi-layer PCBs. These tiny metalized circular holes connect copper traces on different layers to enable signal and power interconnection between layers, and are critical for routing complex circuits.