As an important overvoltage protection device (mainly used for lightning and surge protection), discharge tubes have various packaging forms, which mainly depend on their working principles (gas discharge, semiconductor discharge, etc.), power capacity, application scenarios (circuit board level, equipment inlet end, line protection, etc.), and installation requirements. Here are some common and key types of discharge tube packaging:
Through Hole Packages (THT)
Structural features: This is the most traditional and common form of packaging, with two or more axial or radial lead pins that need to be soldered through through holes on a printed circuit board (PCB).
Typical representative:
Cylindrical Ceramic Gas Discharge Tube (GDT): A cylindrical ceramic tube body with metal caps and leads at both ends. This is the most classic packaging for gas discharge tubes, with various sizes (such as common 5x8mm, 6x8mm, 8x8.5mm, 8.5x10mm, etc.). There are two forms of lead wires: straight insertion and bent leg (90 degrees).
Double in line package (DIP): Some specially designed semiconductor discharge tubes (such as certain TSS) or integrated protection modules may use DIP packages similar to ICs.
Advantages: sturdy structure, strong current carrying capacity (especially suitable for high-power GDT), good heat dissipation, easy installation (especially suitable for manual welding or wave soldering).
Disadvantages: It occupies a large PCB board area and is not suitable for high-density surface mount.
Application scenarios: Power inlet protection (AC/DC), communication ports (such as RJ11/RJ45), signal line inlet protection, and other situations that require high wave resistance.
Surface Mount Device Packages (SMD)
Structural features: No leads or short leads (solder pads), directly mounted on the surface of the PCB, soldered through reflow soldering process. This is the inevitable trend of miniaturization and automated production of modern electronic products.
Typical representative:
Surface mount ceramic gas discharge tube (SMD GDT): typically uses a rectangular ceramic base with metalized pads at both or three ends (for three electrode GDT). The size complies with standard SMD specifications (such as 1206, 1812, 2220, or even larger sizes to meet current requirements).
SMD TSS/SSP: Standard small SMD packages such as SMA (DO-214AC), SMB (DO-214AA), SMC (DO-214AB), etc. are commonly used. These compact packages are suitable for applications with limited space.
Other specialized SMD packages: non-standard SMD shapes designed for specific requirements.
Advantages: Small size, light weight, saving PCB space, suitable for high-density layout and automated SMT production.
Disadvantages: Compared to plug-in packages of the same level, its current carrying capacity may be slightly lower (limited by heat dissipation and volume), and it requires higher requirements for PCB wiring and heat dissipation design.
Application scenarios: portable devices, communication modules, high-speed data cable interfaces (such as USB, HDMI, Ethernet PHY side), space limited circuit board protection.
Leaded Ceramic/Epoxy Packages
Structural characteristics: Similar to plug-in packaging, with leads, but the tube body may be square, rectangular, or other non cylindrical shapes, using ceramic or epoxy resin as insulation packaging material.
Typical representatives: Some specially designed high-power gas discharge tubes or semiconductor discharge tubes, or the discharge tube core is sealed in a customized ceramic or epoxy resin shell and leads out the pins.
Advantages: It can provide specific external dimensions, higher insulation strength, or special electrical characteristics.
Disadvantage: The cost of relatively standardized packaging may be higher.
Application scenarios: occasions that require customized appearance or special performance requirements, such as certain industrial equipment and high-voltage equipment protection.
Metal Can Packages
Structural features: The discharge tube core (especially high-power gas discharge tubes) is sealed inside a metal (such as copper, aluminum) shell, usually with threaded interfaces or flanges for installation and heat dissipation/grounding. The shell itself often serves as an electrode (usually a grounding electrode).
Typical representative:
Coaxial gas discharge tube (Coaxial GDT): commonly used for lightning protection of antenna feeders (such as base station antennas), with coaxial interfaces (N-type, BNC, TNC, etc.). The central conductor is one electrode, and the metal shell is the other electrode (ground).
High power bolt mounted discharge tube: equipped with bolts or flanges, easy to install on the chassis, grounding bar or radiator.
Advantages: Great flow capacity, excellent heat dissipation performance, high mechanical strength, good shielding performance (coaxial type), firm and reliable installation.
Disadvantages: Large size, heavy weight, high cost, installation requires additional space and structural support.
Application scenarios: Communication base station antenna feeder system, entrance of large power supply system, main level lightning protection of important equipment, power system protection.
Modular Packages
Structural features: Integrate single or multiple discharge tubes (possibly of different types, such as GDT+MOV/TVS) with other protective components (such as fuses, thermal trip devices, resistors, inductors) and necessary circuits in a compact housing (plastic, metal, PBT, etc.) to form a complete protection module. Usually provide wiring terminals or connectors that are easy to install.
Typical representatives: various signal surge protector (SPD) modules, power surge protection modules, RJ45 socket modules with protection, etc.
Advantages: High integration, providing a "one-stop" protection solution, simplifying user design and installation, improving system reliability, usually with status indication (such as failure indication).
Disadvantages: Relatively high cost and less flexibility than individual components.
Application scenarios: direct protection of device ports (such as Ethernet ports, telephone ports, RS485 ports, etc.), surge protectors (SPDs) in distribution panels/boxes, and situations requiring plug and play protection solutions.
Summarize key points:
Packaging core objective: To safely and reliably accommodate and protect discharge tubes, provide electrical connection interfaces, meet heat dissipation requirements, and adapt to different installation environments.
Selection criteria:
Surge capability requirements (8/20 μ s, 10/350 μ s, etc.): Determine the packaging size and heat dissipation design (plug-in, metal shell, large-sized SMD).
Working voltage/insulation requirements: affecting the packaging material (good ceramic insulation) and structure.
Installation method: PCB board level (THT/SMD) vs. device port/rack installation (modular/coaxial/bolted).
Space limitation: SMD or micro modules are preferred for miniaturized devices.
Cost: Standard packaging (such as cylindrical GDT, SMA TSS) typically has the lowest cost.
Signal type: High frequency signals (such as overhead lines) require coaxial packaging to maintain impedance matching.
Development trend: While ensuring performance, miniaturization (high-density SMD), integration (modularization), and improving current density and response speed are the main directions for the development of discharge tube packaging.
Understanding these packaging types and their characteristics can help engineers choose the most suitable discharge tube products based on specific application requirements (protection level, space, cost, installation method).