PCB Basics

Introduction to PCBs (Printed Circuit Boards)

PCB stands for Printed Circuit Board, commonly abbreviated as such. In Chinese, it’s known as "Yìnzhì Diànlù Bǎn," also referred to as "Printing Circuit Board" or "Printing Wiring Board." It is a crucial electronic component—serving as both the structural support for electronic components and the medium that facilitates their electrical connections. Because it’s manufactured using advanced electronic printing techniques, it’s aptly named the "printed" circuit board.

PCB Design The design of a printed circuit board is based on the circuit schematic, enabling the realization of the functions required by the circuit designer. PCB design primarily refers to layout planning, which involves carefully considering factors such as the arrangement of external connections, optimal placement of internal electronic components, efficient routing of metal traces and vias, electromagnetic shielding, and thermal management. A well-designed PCB layout not only helps reduce production costs but also ensures excellent circuit performance and effective heat dissipation. Commonly used PCB design software includes Protel 99SE and DXP.

PCB Classification Classified by the number of circuit layers: these include single-sided boards, double-sided boards, and multilayer boards. Common multilayer boards typically consist of 4 or 6 layers, while more complex designs can have over ten layers.

There are three main types of PCB board classifications:

1. Single-Sided Boards: On the most basic type of PCB, components are mounted exclusively on one side, while the wiring is routed entirely on the opposite side. Since the conductive traces appear only on one surface, these boards are referred to as single-sided PCBs. However, due to the significant design limitations—such as the inability to route wires across each other, forcing them to follow separate, non-intersecting paths—single-sided boards were primarily used in very early circuit designs only.

2. Double-Sided Boards: These circuit boards have wiring on both sides, but to utilize the conductors on both sides, proper electrical connections between the two layers are essential. The "bridges" that link these circuits are called vias. Vias are small holes on the PCB that are either filled or coated with metal, enabling them to connect conductive paths from one side to the other. Since double-sided boards occupy twice the area of single-sided boards and allow wires to cross over each other (by routing traces onto the opposite side), they are better suited for more complex circuits compared to their single-sided counterparts.

3. Multi-Layer Boards To maximize the available wiring area, multi-layer boards utilize multiple single- or double-sided circuit boards. For instance, a printed circuit board constructed with one double-sided layer as the inner core, paired with two single-sided layers on the outer sides—or alternatively, two double-sided layers forming the inner core and two single-sided layers attached to the exterior—can be interconnected via an alignment system and insulating adhesive materials. When these layers are stacked alternately, with conductive patterns precisely routed according to design specifications, the result is a four-layer or six-layer PCB, commonly referred to as a multi-layer printed circuit board. The number of layers in the board directly corresponds to the number of independent wiring layers it contains; typically, the total number of layers is even, always including the two outermost layers. Most modern motherboards feature a structure ranging from 4 to 8 layers, though technically, PCBs with nearly 100 layers are possible in theory. Large-scale supercomputers often rely on highly multi-layered motherboards. However, as these advanced systems can now be effectively replaced by clusters of conventional computers, ultra-thick multi-layer boards are gradually becoming less common. Due to the tight integration of each layer within the PCB, it’s usually challenging to determine the exact number of layers at a glance. Still, if you examine the motherboard closely, you may still be able to count them.

Classified by rigidity: divided into standard circuit boards and flexible circuit boards.

The raw material for PCBs: Copper-clad laminate is the substrate material used to manufacture printed circuit boards. It serves as a support for various components and enables either electrical connections or insulation between them.

A PCB is a printed circuit board (PCB board)—simply put, it’s a thin board equipped with integrated circuits and other electronic components.

A bare board—without any components mounted on it—is often referred to as a "Printed Wiring Board (PWB)." The board's base material itself is made from an insulating, heat-resistant, and highly rigid substance that doesn’t easily bend. On the surface, you’ll notice tiny conductive traces made of copper foil, which was originally coated across the entire board. During the manufacturing process, portions of the copper foil are selectively etched away, leaving behind a delicate, network-like pattern of fine wiring. These traces are called the conductor pattern—or simply the wiring—and they serve to establish electrical connections between the components mounted on the PCB.

Typically, PCBs are green or brown—these are the colors of the solder mask, an insulating protective layer that shields copper traces and prevents components from being soldered to the wrong areas. On top of the solder mask, a layer of silkscreen is often printed, usually in white, to clearly mark the positions of individual components on the board with text and symbols. To secure components onto the PCB, their leads are directly soldered onto the copper traces. In the simplest type of PCB—known as a single-sided board—components are mounted exclusively on one side, while the copper traces are concentrated entirely on the opposite side. This setup requires drilling holes through the board so that component leads can pass through and connect to the other side, where they’re ultimately soldered. As a result, the two sides of the PCB are commonly referred to as the Component Side and the Solder Side, respectively.

If there are certain components on the PCB that need to be removable or reattachable after manufacturing, those parts will be fitted using a socket. Since the socket is directly soldered onto the board, the components can be easily assembled and disassembled as needed.

When connecting two PCBs together, we typically use what’s commonly known as an "edge connector," often referred to as the "gold finger." These connectors feature numerous exposed copper pads, which actually serve as part of the PCB’s wiring layout. During connection, one PCB’s gold fingers are inserted into the corresponding slot on the other PCB—commonly called an expansion slot. In computers, devices like graphics cards, sound cards, or other similar interface cards rely on edge connectors to link directly to the motherboard.

The printed circuit board, featuring intricate copper wiring that connects electronic components, is carefully and neatly etched onto a single sheet of material. It serves as the primary structural support for mounting and interconnecting electronic components, making it an indispensable foundational part of all electronic devices.

A printed circuit board is a flat, non-conductive material upon which pre-drilled holes are typically designed to mount chips and other electronic components. These component holes allow the metal traces—predefined and printed directly onto the board—to create electrical connections. After the component leads are inserted through the PCB, they are soldered in place using conductive metal wires, forming the final circuit.

PCBs can be categorized into single-sided boards, double-sided boards, multilayer boards with four or more layers, and flexible boards, depending on their application areas. Generally speaking, the more complex the functionality of an electronic product, the longer its circuit paths and the greater the number of connection pins required—resulting in PCBs that demand a higher number of layers. This is especially true for advanced consumer electronics, information technology devices, and communication products. Meanwhile, flexible boards are primarily used in applications where bending or folding is necessary, such as in laptops, cameras, automotive dashboards, and other similar products.