Marquages ​​courants des PCB et leur analyse fonctionnelle

Common PCB Markings and Their Applications

1. PCB Castellated Holes (Mouse Bites)

Castellated holes, Comme son nom l'indique, are small holes used in PCB panelization to facilitate separation between individual boards. These holes are typically arranged in specific patterns, forming a perforated edge similar to a postage stamp. This design helps ensure clean and consistent depaneling while also simplifying manufacturing processes. The size and number of these holes are determined based on board material hardness and the required separation force to ensure a smooth depaneling process.

PCB Castellated Holes

Applications:
Commonly used in scenarios where multiple small PCBs are panelized together and later separated in mass production, especially in consumer electronics manufacturing and assembly.

2. Types of PCB Vias

Vias on a PCB are generally categorized into plated and non-plated types. They serve two main purposes:

• Plated vias enable electrical connections between internal layers of a PCB multicouche.
• Non-plated vias act as insulation, preventing unintended electrical connections between pads.

En plus, some designs include arrays of small vias around a main via to improve connection reliability. This is especially important in high-density PCBs, as it helps reduce electrical impedance and prevents circuit failures caused by unstable current flow.

Applications:
Widely used in multilayer PCBs to ensure smooth signal transmission between layers, especially in high-density integrated circuits and high-frequency circuit boards.

3. Solder Thieving Pads (Anti-Solder Bridging Pads)

Solder thieving pads are auxiliary pads designed to prevent solder bridging during soudure d'onde. Dans ce processus, SMD (Surface-Mount Device) components may experience excessive solder accumulation, leading to short circuits between adjacent pins. These pads “steal” excess solder during the process, drawing it away and preventing bridging.

Applications:
Commonly used in wave soldering and SMT (Technologie de montage de surface) processes as an important measure to ensure soldering quality.

4. Fiducial Marks (Mark Points)

Fiducial marks are positioning references designed on PCBs, typically made of exposed copper or copper foil. They serve as reference points for automated equipment, enabling machines to accurately align and assemble components. These marks are usually placed on panel edges, component areas, or at the four corners of the PCB. Their shapes and sizes are standardized to ensure precise recognition.

Applications:
Widely used in automated pick-and-place and inspection systems to guarantee accurate component placement.

5. Spark Gaps

Spark gaps, also known as air-gap protection, are used in PCBs for voltage protection. They utilize air as an insulator; under high voltage, air can ionize and create a spark between two terminals, thereby protecting sensitive components in the circuit. Spark gap design must be handled carefully and is typically used as a temporary or supplementary protection method rather than a primary solution.

Applications:
Common in circuits exposed to high-voltage pulses or electrostatic discharge (ESD), such as power management boards and voltage protection circuits.

6. PCB Conductive Buttons

PCB conductive buttons consist of two interleaved but unconnected terminals. When an external rubber button (usually made of conductive material) is pressed, it bridges the terminals, forming a closed circuit. This design is commonly used in devices requiring mechanical input.

Applications:
Used in low-voltage control systems such as key switches and simple control circuits, often found in consumer electronics like remote controls and calculators.

7. Fuse Traces

Fuse trace design is a low-cost PCB protection method that uses a narrowed trace to function as a one-time fuse. When the current exceeds a specified limit, the trace melts and breaks the circuit. While simple and cost-effective, this protection is irreversible.

Applications:
Commonly used in devices with higher current loads and strict cost constraints, such as basic current protection in development boards like Arduino.

8. PCB Slots (Isolation Slots)

PCB slots are used in high-voltage or high-current circuits to enhance insulation. These slots prevent repeated electrical discharge from carbonizing the PCB material, which would otherwise reduce insulation performance and potentially cause short circuits. By creating air gaps, slots increase the creepage distance.

Applications:
Widely used in power equipment and switching power supply boards to improve long-term reliability.

PCB Marking Standards and Design Principles

(1) Core Standards: Clarity, Cohérence, Durabilité

• Readability: Markings must be clear and legible. Silkscreen text should not be smaller than 0.8 mm × 0.8 mm and must not overlap with pads or vias.
• Cohérence: Follow international standards such as IEC and IPC. Reference designators and symbol formats should be uniform, avoiding non-standard custom markings.
• Durabilité: Silkscreen materials should withstand high temperatures and solvents, ensuring markings remain intact and legible after soldering and cleaning processes.

(2) Design Principles: Practicality First, Aesthetics Second

• Avoid Critical Areas: Markings must not cover pads, vias, or test points to prevent interference with soldering and measurement.
• Proximity Labeling: Polarity and orientation markings should be placed close to the corresponding components to minimize confusion.
• Simplicity: Avoid redundant information; use symbols instead of lengthy text (Par exemple, “⚡” instead of “High Voltage Warning”) to improve recognition efficiency.

Practical Value of PCB Markings

In electronics manufacturing, standardized PCB markings can reduce assembly error rates by over 80% and shorten repair time by 60%:

• Production: Automated placement relies on fiducial marks, while manual assembly uses reference designators and outlines for efficient operation.
• Entretien: Technicians can quickly locate faulty components using reference and electrical markings, and verify batch-related issues through version markings.
• Market: Certification and environmental markings act as a “passport” for global markets, while safety warnings reduce usage risks and enhance product reliability.

Conclusion

Although PCB markings are not the “functional core” of a circuit, they serve as the “invisible foundation” for stable operation and efficient production of electronic devices. From standardized planning during design, to precise printing in manufacturing, and intuitive guidance during use, every small marking conveys critical information that ensures the orderly development of the electronics industry. As electronic devices continue to evolve toward miniaturization and higher density, PCB marking design will become increasingly refined, and its “navigation” role will grow ever more indispensable.