Precision resistors are often associated with high-precision resistors. The accuracy represents the accuracy of the resistance value of the resistor. In fact, this accuracy is affected by many factors. These factors that affect the accuracy of the resistance value are collectively referred to as "stress". Stress comes from many aspects, such as changes in ambient temperature, self-heating generated after the resistor itself is energized, pressure or tension from the PCB, moisture in the external environment, and even corrosive gases, as well as welding, pulse, overload, static electricity , radiation, etc. All the "stress" mentioned above will change the resistance value of the resistor, that is to say, it will affect the resistance value accuracy of the resistor. So what kind of resistor is a precision resistor? The answer is a resistor with both stability and accuracy.

(1) Precision thick film resistors

Through continuous improvement of thick film resistor pastes, the most sophisticated thick film resistor technology can achieve a temperature drift of ±5ppm/°C, and even by using multiple thick film resistor chips that can compensate for each other, it can finally reach ±2ppm/° C's warm drift. Its highest accuracy can also reach ±0.01%. Precision thick film resistors are the mainstream technology in high-voltage, high-resistance, and high-precision applications. The disadvantage of thick film resistors is that it is difficult to achieve high precision and low temperature drift in the low resistance part, the noise index is not good, and the long-term stability is generally worse than other precision resistors.

(2) Precision thin film resistors

The technological development of precision thin film resistors represents the precision resistance technology that can be used in a large number of commercial applications, and it is also the most popular precision resistance technology at present. Through long-term multilayer film deposition, high-precision resistance adjustment and post-screening, the optimal precision thin-film resistor can achieve a temperature drift of ±2ppm/°C, an accuracy of ±0.01%, and good long-term stability. . The disadvantage is that the power is not large, the low resistance part is not good, it is not antistatic, the power coefficient is poor, it is difficult to meet the supply of small batches, and the consistency of different batches is not good.

(3) Precision metal film resistors

The indicators of precision metal film resistors are similar to those of precision thin film resistors. Wafer precision metal film resistors tend to be replaced by chip precision film resistors, but pin precision metal film resistors are still the mainstream low-cost precision resistor technology. Like precision thin film resistors, the resistance adjustment will cause a hot spot effect, which affects the stability and reliability of the resistor.

(4) Precision wirewound resistors

As the earliest precision resistor technology, the temperature drift of high-precision wirewound resistors can be ±1ppm/°C, and the accuracy can be ±0.001%, which is impossible for thin-film and thick-film resistors. The best precision wirewound resistors have a resistance value close to 50M, which is suitable for ultra-precision high-resistance applications. Due to the development of other resistor technologies, precision wirewound resistors tend to be on the verge of being eliminated because of their high price and disadvantages such as inductance.

(5) Precision foil resistors

Although the precision foil resistor was invented as early as 1962, it is still the most precise resistor technology so far. By sticking the nickel-chromium alloy on the ceramic substrate for stress balance, the temperature drift close to zero is obtained, and the resistance pattern is etched by laser. As well as adjusting the resistance, an accuracy of up to ±0.001% can be obtained. The best foil resistors have a 6-year storage resistance drift of only ±2ppm, antistatic, non-inductive and non-capacitive, no hot spot design, low noise, and low voltage coefficient. The disadvantage of foil resistors is that the resistance value cannot be very high. The maximum size of the chip resistor can only be up to 150K, and the maximum size of the pin resistance can only be up to 2M.