Precautions for using PTC thermistors for overcurrent protection

1. Soldering

During soldering, ensure that the PTC thermistor is not damaged by excessive heating. The following maximum temperatures, maximum times, and minimum distances must be observed:

Dip soldering

Soldering iron

Bath temperature

Maximum 260°C

Maximum 360°C

Soldering time

Maximum 10s

Maximum 5s

Minimum distance from the PTC thermistor

Minimum 6mm

Minimum 6mm

Harsh soldering conditions may cause changes in resistance.

2. Coating and Potting

When applying coatings and potting to PTC thermistors, mechanical stresses due to differential thermal expansion during curing and subsequent handling must not be allowed. Use potting materials or fillers with caution. Do not exceed the PTC thermistor's upper temperature limit during curing. Furthermore, the potting material must be chemically neutral. Reduction of the titanate ceramic in a PTC thermistor may result in a decrease in resistance and loss of electrical properties. Changes in heat dissipation caused by infusion may cause localized overheating in the PTC thermistor, leading to its destruction.

3. Cleaning

Mild cleaning agents such as Freon, trichloroethane, or tetrachloroethylene are suitable for cleaning. Ultrasonic cleaning can also be used, but some cleaning agents may damage the thermistor's performance.

4. Storage Conditions and Storage Life

If properly stored, PTC thermistors have no storage limit. To maintain solderability,

they should be stored in a non-corrosive atmosphere, paying attention to humidity, temperature, and container material. Components should be stored in their original packaging whenever possible. Touching the metal coating of an unsoldered PTC thermistor may degrade solderability. Exposure to excessive humidity or high temperatures may affect the performance of some products, such as the solderability of tin-lead components. However, they can be stored for extended periods under normal electrical component storage conditions.

5. Precautions

To avoid accidents such as failure, short circuit, or burnout of PTC thermistors, pay special attention to the following when using (or testing) PTC thermistors:

Do not use (or test) PTC thermistors in oil, water, or flammable or explosive gases;

Do not use (or test) PTC thermistors above their "maximum operating current" or "maximum operating voltage" ratings.