PCBタイプについて

Printed Circuit Boards (PCBs) are essential components in electronic devices, serving as the backbone for connecting and supporting various electronic components. PCBs come in several types, each with its own characteristics and applications. Here’s a brief introduction to the main PCB types:

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    Introduction to general PCB types

    General PCB typesCircuit boards are mainly divided into Flexible Printed Circuits (FPC), Printed Circuit Boards (PCB), and Rigid-Flex PCBs (Rigid-Flexible Printed Circuit Boards).

    PCB (Printed Circuit Board): Also known as printed wiring boards, they are widely used in the production of electronic products.

    FPC (Flexible Printed Circuit): FPCs are favored for their high wiring density, light weight, thin thickness, and good flexibility. For example, one of our current products uses FPC for wiring due to its light weight and good flexibility.

    Rigid-Flex PCB: Rigid-Flex PCBs combine both flexible and rigid board materials through lamination processes. They integrate the characteristics of FPC and PCB, but the production process is more complex, leading to lower yield rates and longer production cycles.

    Other PCB types

    Classification by Number of Layers

    Based on the number of copper foils, PCBs are classified as single-sided, double-sided, and multi-layer boards.

    Single-Sided Boards: Conductive traces are only on one side, limiting wiring design. They are used in simple circuits or where cost is a concern.

    Double-Sided Boards: Conductive traces are on both sides, allowing for more complex wiring. They are used in circuits with simple layouts and less densely packed components.

    Multi-Layer Boards: Multiple single or double-sided boards are stacked together with insulating layers between them. Common multi-layer boards have 4 to 8 layers.

    Classification by Substrate Material

    Common substrate materials include phenolic paper laminate, epoxy paper laminate, polyester glass mat laminate, and epoxy glass fabric laminate.

    Additionally, copper-clad boards can be categorized into three types: FR-4 copper-clad boards, metal-based copper-clad boards, and high-frequency copper-clad boards.

    1. FR-4
    FR-4 copper-clad laminate is a type of conventional copper-clad board based on fiberglass material and epoxy resin substrate, widely used in the electronics industry. Its advantages include excellent insulation performance, high mechanical strength, good processing properties, and strong resistance to chemical corrosion, making it the preferred material for manufacturing standard circuit boards.

    2. Metal Substrate
    Metal substrate copper-clad laminate uses metals such as aluminum, copper, or iron as the base material, with a layer of copper foil covering it. It is typically employed in electronic components requiring high thermal conductivity and strength. Its advantages lie in excellent thermal conductivity, high mechanical strength, good dimensional stability, and outstanding performance in high-temperature environments, suitable for applications in automotive electronics, LED lighting, power supplies, and other fields.

    3. High-Frequency
    High-frequency copper-clad laminate adds a layer of special polymer materials such as polyimide on the basis of conventional copper-clad laminate, used for high-speed transmission circuits ranging from several hundred megahertz to ultra-high frequencies. Its characteristics include low dielectric constant, good stability, high mechanical strength, and precise impedance control, making it suitable for applications in communication base stations, satellites, and other fields.

    4. PTFE :
    (Polytetrafluoroethylene):
    PTFE exhibits excellent insulation and high-frequency characteristics, commonly used in high-frequency circuits and RF applications.

    5. Polyimide :
    Polyimide offers outstanding high-temperature stability and flexibility, suitable for high-temperature environments and flexible circuit boards.

    6. FR-1, FR-2, FR-3:
    Common inexpensive insulation materials used for applications with lower requirements.

    Classification by Via Type

    Based on the type of vias, PCBs are categorized into through-hole, blind hole, and buried via.

    Through-Hole: The hole traverses the entire board from one outer layer to the other.

    Blind via: The hole starts from one surface (outer layer) and ends at an inner layer without penetrating the entire board.

    Buried Via: Both ends of the hole are within the inner layers of the board, connecting only internal layers.
    PCB vias types

    Classification by Presence of Copper

    PCBs are classified into plated through-hole (PTH) and non-plated through-hole (NPTH) types based on the presence of copper in the holes.

    Plated Through-Hole (PTH): In PTH, the vias have copper plating inside, serving as conductive pathways. These are commonly used for routing traces on the board.

    Non-Plated Through-Hole (NPTH): NPTH refers to vias without copper plating inside, often used for mounting components or as non-conductive holes on the board.

    In reality, most PCBs contain a combination of vias with and without copper plating during the manufacturing process.

    Surface Treatment Classification

    To prevent oxidation of copper, various surface treatments are applied, including:

    – Hot Air Level Soldering (HAL)
    – Electroless Nickel/Immersion Gold (ENIG)
    – Immersion Tin/Chemical Tin
    – Immersion Silver/Chemical Silver
    – Organic Solderability Preservatives (OSP)
    – Gold Plating/Flash Gold
    – Carbon Oil
    – Peelable Solder Mask
    – Plating Gold Finger/Edged Contact/Connecting Finger

    Classification by Copper Thickness

    Based on the thickness of the copper foil, copper-clad boards can be categorized into three types: thick copper, medium copper, and thin copper.

    1. Thick Copper:
    Thick copper boards typically have a copper foil thickness of over 70μm, sometimes even exceeding 300μm. They are primarily used in high-power electronic components and specialized circuit boards.

    2. Medium Copper:
    Medium copper boards have a copper foil thickness ranging from 35μm to 70μm, making them the most common type of copper-clad boards. They are suitable for the production of most general-purpose circuit boards and medium-power electronic components.

    3. Thin Copper:
    Thin copper boards have a copper foil thickness below 18μm and are commonly used in the fabrication of high-density interconnect (HDI) PCBs and flexible printed circuit boards (FPCs). They are increasingly widespread in the electronics industry.

    Classification by Color

    Circuit boards come in many different colors. Common circuit board colors include green, red, blue, black, yellow, and others. Different colored circuit boards are typically used for different applications and scenarios. For example, green circuit boards are the most common and widely used in electronic products, while red circuit boards are often used for high-speed signal transmission. Blue circuit boards are commonly employed in special applications such as medical equipment. Additionally, circuit boards can be customized to other colors to meet specific requirements.

    PCB boards come in various colors primarily determined by different substrate materials and manufacturing processes. Below are some common PCB colors and their reasons:

    1. Green PCB:
    Green is the most common and economically feasible color choice for PCBs. This is because traditional FR-4 (fiberglass-reinforced epoxy resin) substrate manufacturing processes use green photosensitive dye to print PCB patterns and markings, forming the solder mask layer. The green color provides good contrast, making labels and traces on the circuit board clearly visible.

    2. Red PCB:
    Red PCBs are relatively common in specific applications such as high-end communication equipment and military electronics. They typically use high-temperature-resistant red photosensitive dyes, offering good thermal stability and weather resistance suitable for high-temperature and harsh environment applications.

    3. Blue PCB:
    Blue PCBs are also relatively common and are often associated with specific brands and products. They utilize blue photosensitive dyes to form the solder mask layer, providing good appearance and recognition.

    4. Black PCB:
    Black PCBs are more common in high-end applications such as high-performance computers and audio equipment. Black PCBs can provide a sense of high quality and professionalism and also offer good heat dissipation performance suitable for applications requiring high-power processing.

    5. White PCB:
    White PCBs have a clean and neat appearance, becoming increasingly popular. However, due to the tendency of white PCBs to conceal traces, they are not the preferred choice. Nevertheless, white PCBs provide excellent contrast in black silk screen printing.

    結論

    From the simplest of devices to the most complex systems, PCBs serve as the foundational framework upon which innovation thrives. Understanding the diverse array of PCB types is not only crucial for engineers and designers but also for enthusiasts eager to grasp the nuances of electronic architecture.

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