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When it comes to the packaging format of NTC thermistors, there are generally glass encapsulation, epoxy resin, columnar encapsulation and so on. Each encapsulation format has its unique advantages and application scenarios. And among them, epoxy resin encapsulation occupies a certain proportion. So, what are the epoxy resin encapsulated thermistors?
Epoxy-coated NTC thermistor temperature sensors are in the form of a tear-drop bead with two radial leads. These NTC thermistor temperature sensors are typically used in applications near humid environments. It also increases the mechanical strength of electronic components and reduces the risk of physical damage during handling, transportation and operation.
The following are three common thermistors encapsulated in epoxy resin:
- Bead-Type Thermistors
- Disc and Chip Thermistors
- Surface-Mount Thermistors (SMD)
In the article, we will discuss the definition of epoxy encapsulated thermistor, introduce the above 3 types specifically, and the advantages of using it.
What is epoxy encapsulated thermistor
Epoxy coated thermistor sensors are waterproof temperature sensors, usually with tinned copper leads. They are used for temperature measurement, control and compensation. Thermistors that detect temperature changes are first first soldered to leads of the relevant gauge and then encapsulated in multiple layers of epoxy resin to protect them from damage and keep them safe from the environment.
Differences Compared To Glass Packaging
Glass Encapsulated Thermistors: The production process is much more complex than epoxy encapsulation. The thermistor core is first connected using Durometer wire (uninsulated) and then encapsulated in a glass case. The size of the glass case varies from 0.8mm, 1.3mm, 2.3mm, etc. The whole process is completed by high temperature sintering, which makes glass encapsulated thermistors resistant to high temperature.
Epoxy encapsulated thermistors: These thermistors are manufactured by connecting the thermistor core to an insulating wire (e.g. PVC or Teflon) and then covering the assembly with epoxy resin. The minimum head size can be as small as 2.0 mm. This process is simpler than glass encapsulation and therefore more suitable for mass production.
3 Common Epoxy Encapsulated NTC Thermistors
As seen above, epoxy encapsulated NTC thermistors are a common type of thermistor due to their ease of mass production. Here, we will discuss three common types of these thermistors and their main applications:
Bead-Type Thermistors
Beaded thermistors with epoxy coated chip thermistors and glass seals. Glass sealed bead thermistors are used for applications requiring small size, fast response time, high operating temperature (up to 450oC), reliability and stability, and/or self-heating use.
Features
- Coated with epoxy resin for insulation and environmental protection
- Typically mounted on leads
Applications
for temperature measurement in medical devices, automotive sensors and electronic circuits.
Disc and Chip Thermistors
They are flat thermistors with a disk or chip shape. These devices provide extremely high precision and temperature measurements for a variety of applications. Precision resistors are available with tolerances up to 1%. Standard resistor tolerances are 5% to 20%.
Features
- Encapsulated in epoxy resin for ruggedness and moisture resistance.
- Fast thermal response time
- Wide ohmic value range
Applications
Used for battery packs, heating control and overcurrent protection.
Aerospace, military, appliance, medical and automotive
Surface-Mount Thermistors (SMD)
They offer excellent accuracy and sensitivity, with fast response times, enabling quick adjustments and real-time operation in temperature-sensitive systems. Their compatibility with automated assembly processes simplifies manufacturing, making them ideal for mass-production electronic devices.
Features
- Coated with a thin epoxy resin layer for protection
- Fast response
- High accuracy
Applications
Used for smartphones, tablets, and IoT devices, HVAC, medical applications
Comparison Table of the Three Types
| Type | Structure | Temperature Range | Unique Benefit |
| Bead-Type Thermistors | Small bead with radial or axial leads, epoxy-coated. | Typically -40°C to +125°C. | High precision and fast response time. |
| Disc and Chip Thermistors | Flat, disc-shaped or chip-style, epoxy-encapsulated. | Often ranges from -40°C to +150°C or higher. | Reliable in high-temperature and high-stress environments. |
| Surface-Mount Thermistors (SMD) | Compact, flat design for surface mounting with epoxy coating. | Typically -55°C to +125°C. | Space-saving and ideal for miniaturized, high-volume applications. |
Why Use Epoxy Sealing?
As can be seen from the above, epoxy encapsulation is easy to produce in large quantities. The following are other advantages of choosing to use this type of encapsulation:
Protection Against The Effects Of Humidity
The epoxy coating or potting material provides some protection against moisture and prevents water vapor from penetrating the thermistor sensor. This suggests that epoxy encapsulated thermistors are indefinitely protected against moisture penetration.
Provide Physical Protection
Sealing NTC thermistors with epoxy resins protects sensors from accidental impacts during manufacture and operation: impacts that can cause thermistors to lose critical tolerances needed for long-term accuracy. In addition, it provides effective protection in applications where thermistor probes are susceptible to high-energy or high-frequency vibration, such as those associated with mining equipment, industrial vehicles, and aircraft.
Electrical Insulation Protection
The type of epoxy used for sealing also provides electrical insulation protection for NTC thermistors. Accidental electrical contact with other components, metal enclosures or chassis parts can damage the thermistor. The epoxy coating also prevents oxidation from forming on the surface of the thermistor.
Guaranteed flame retardant and flame retardant
Epoxy coatings are flame retardant and flame retardant. Industrial grade epoxy resins have an important property that originates from an additive in the epoxy coating. It contributes to the overall safety of the product.
Key Considerations When Choosing an Epoxy Encapsulated NTC Thermistor
Selecting the right epoxy encapsulated NTC thermistor involves evaluating several important factors that directly affect performance, reliability, and cost-effectiveness in your particular application. The following are key considerations to keep in mind:
1. Temperature Range
Ensure that the thermistor can operate effectively at the extreme temperatures of your application. Some epoxy encapsulated NTC thermistors are designed for high-temperature environments (up to 150°C or higher), while others are better suited for low or medium temperature ranges.
2. Application Scenarios
If the thermistor is to be used in an automotive, industrial, or other environment prone to vibration or physical stress, choose a thermistor with a rugged epoxy encapsulated package that can withstand these conditions without compromising accuracy or performance.
3. Resistance Value
Nominal Resistance: The nominal resistance of a thermistor at a given reference temperature (usually 25°C) is one of the most important factors in selecting a suitable thermistor. The resistance value should match the requirements of the circuit or application. Thermistors with higher resistance values are generally more sensitive to small changes in temperature, but they may have slower response times or lower power handling capabilities.
Conclusion
NTC thermistor packaged by epoxy resin is widely recognized due to its durability in various temperature sensing applications. Whether you are choosing beads, discs and chip models, or surface installation versions, they have their unique advantages and characteristics. Epoxy sealing not only enhances the resistance of environmental factors such as water and vibration, but also provides indispensable heat insulation and mechanical protection. This makes them very suitable for industries from automotive and aerospace to consumer electronics and medical equipment.
When selecting the right epoxy-encapsulated thermistor, it’s important to consider factors like temperature range, application scenarios, and resistance values to ensure optimal performance and longevity. With their robust design and easy mass production capabilities, epoxy-encapsulated NTC thermistors are a reliable choice for applications requiring precision temperature control in both standard and challenging environments.
DTTTEK provides a thermistor of the quality and reliable epoxy resin packaging, which flexibly sets up and supports a large number of ordering. Our products meet industry standards and customer specifications, and the delivery cycle is short. Get the free quote today!
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