PTC thermistor stands for positive temperature coefficient thermistor and is a key component in modern electronics. They are characterized by their ability to increase resistance as temperature increases, a property that has driven their widespread use in a variety of electronic circuits.
Structure and function of PTC thermistor
The core of a PTC thermistor is made of ceramic materials, of which barium titanate-based ceramics are particularly common. These ceramics undergo a doping process that gives them semiconductor functionality. This involves injecting selected ions into the material's crystal lattice, effectively displacing some of the barium or titanate ions. Therefore, this introduces free electrons, which gives the material conductivity. The fascinating aspect lies in the material's response to an increase in temperature to a certain threshold, known as the Curie temperature. Beyond this point, due to the significant increase in the grain boundary barrier, the resistance value surges, thus exhibiting an obvious PTC effect. At lower temperatures, the material exhibits low resistance, thanks to a high dielectric constant and polarization strength, which counteracts the formation of potential barriers. In contrast, at high temperatures, these properties decrease significantly, resulting in increased resistance.
Manufacturing process of PTC thermistor
The manufacture of PTC thermistors is a testament to the precision of materials science and engineering. It starts with the preparation and mixing of specific raw materials such as barium carbonate and titanium dioxide, adhering to strict electrical and thermal standards. After a series of meticulous wet milling, dehydration and drying, the mixture is formed into the desired shape using dry pressing technology. Subsequent sintering at high temperatures produces a ceramic body with the desired microstructure. The final stage of the process is surface metallization and electrode connection, preparing it for electrical connections. After resistance sorting, packaging and thorough testing, these thermistors are ready for deployment in a variety of electronic applications