What are the packaging forms of varistors?

There are various packaging forms for varistors, which can be mainly divided into the following categories based on different application scenarios, power requirements, and installation methods:
1、 Plug in packaging (lead type)

Disc Type

Structure: Silver electrodes are coated on both sides of the ceramic substrate, metal leads are welded (radially or axially), and the outer layer is covered with insulating materials such as epoxy resin or silicone.
Size series: The base diameter ranges from Ø 5mm to Ø 53mm (such as Ø 5, Ø 7, Ø 10, Ø 14, Ø 20, etc.), and the finished product has a slightly larger encapsulation layer.
Application: General power protection, household appliances, industrial equipment, etc. The current capacity increases with size (such as up to 10kA for a diameter of 20mm).

Block Type

Typical specifications: such as 34 × 34mm (634 series), with a structure similar to a circular disc but designed in a square shape.
Features: Better heat dissipation performance, suitable for high-energy absorption scenarios (such as lightning protection modules).

Lead form

Radial lead (dual pins on the same side): commonly used for power supply parallel protection.
Axial lead (pins at both ends): suitable for board level layouts with limited space.
2、 Surface mount packaging (SMD)
Structure: Leadless design, directly mounted on the PCB surface to reduce parasitic inductance.
Advantages: Small size, fast response (<25ns), suitable for high-frequency circuits and micro devices (such as mobile phones and laptop power supplies).
Typical models: such as 0402, 0603, 1206 series, etc., with a voltage range of 18V-1800V.
3、 Modular packaging
High current module
Multiple varistors are integrated in parallel, with a current capacity of over 70kA, used for lightning protection in high-voltage distribution systems and substations.
High voltage module
Multiple pieces connected in series (such as power lightning arresters) can work continuously at voltages up to tens of thousands of volts to cope with high-voltage transient impacts.
4、 Special industrial packaging
Bulk Type: Reinforced with a metal casing or ceramic substrate, it has strong heat dissipation and is used in high-power scenarios such as industrial motors and frequency converters.
Epoxy sealing type: fully sealed design, moisture-proof and dustproof, suitable for harsh environments (such as automotive electronics, outdoor equipment).
Key points for packaging selection
Advantages and limitations of packaging types in applicable scenarios
Plug in (wafer/square) universal power protection, high household electrical current flow, low cost, large size, high parasitic parameters
SMD high-frequency circuits, portable devices with small size, fast response and low flow rate
Modular high voltage/high current systems (such as power grids, industries) with ultra-high energy absorption capacity, high cost, and complex installation
Special industrial high temperature/high humidity environment with high protection level, strong reliability, and high customization requirements
The packaging form of varistors needs to be selected comprehensively based on voltage level, current requirements, space limitations, and environmental factors. For example:
Surface mount or small-sized plugins (such as 5D/7D series) are preferred for ordinary electronic products;
Power inlet protection is commonly packaged in circular discs ranging from 10mm to 20mm in diameter;
Extreme environments such as automobiles and power grids require modular or reinforced packaging.
Note: Package parameters (such as size and flow rate) should refer to the specific model manual, as there may be differences among different manufacturers.