Introduction and Classification of SMT Chip Resistors (Part 2)

2) Thin film resistors Thin-film resistors are made by evaporating materials with a certain resistivity on the surface of insulating materials by evaporation-like methods. Generally, the insulating material commonly used for this kind of resistors is a ceramic substrate. Thin-film resistors use vacuum evaporation, magnetron sputtering and other process methods. The difference in materials and processes between thick film resistors and thin film resistors directly leads to the difference in performance of the two types of resistors. Thick film resistors generally have poor accuracy, 10%, 5%, and 1% are common accuracy, while thin film resistors can achieve 0.01% accuracy and 0.1% accuracy. At the same time, the temperature coefficient of thick film resistors is difficult to control, and is generally large.

Similarly, thin film resistors can achieve very low temperature coefficients, so that the resistance value changes very little with temperature, and the resistance value is stable and reliable. Therefore, thin film resistors are often used in various instruments and meters, medical equipment, power supplies, power equipment, electronic digital products, etc.

3) Thermistor Thermistor is a type of sensitive element, according to the temperature coefficient is divided into positive temperature coefficient thermistor (PTC) and negative temperature coefficient thermistor (NTC). The typical characteristic of thermistor is that it is sensitive to temperature and exhibits different resistance values at different temperatures. Positive temperature coefficient thermistor (PTC) has a higher resistance value when the temperature is higher, and negative temperature coefficient thermistor (NTC) has a lower resistance value when the temperature is higher. They are both semiconductor devices. The thermistor will remain inactive for a long time; when the ambient temperature and current are in zone c, the heat dissipation power of the thermistor is close to the heating power, so it may or may not operate. When the ambient temperature is the same, the action time of the thermistor is shortened sharply with the increase of the current; when the ambient temperature is relatively high, the thermistor has a shorter action time and smaller maintenance current and action current.