Getting Started: Chip Resistors Classification, Rated Power and Operating Voltage

Chip resistors are divided into the following categories:

Rated power and working voltage of chip resistors

The power of a chip resistor refers to the power generated by the Joule thermal resistance when current passes through it. It can be calculated according to Joule's law: P=I2R.

Rated power: refers to the maximum allowable power at a certain temperature, usually refers to the rated power when the ambient temperature is 70°C.

Rated voltage: The rated voltage can be calculated according to the following formula.

Rated voltage (V) = √

Rated power (W) × nominal resistance (Ω)

Maximum operating voltage: The maximum voltage allowed to be loaded across the chip resistor.

The relationship between the chip resistor package, power and voltage is as follows:

Note:

When designing and using chip resistors, the maximum power cannot exceed its rated power, otherwise its reliability will be reduced. Generally, it is designed and used at 70% of the rated power. It also cannot exceed its maximum operating voltage, otherwise there is a risk of breakdown.

Generally, the maximum operating voltage is derated to 75%. When the ambient temperature exceeds 70°C, it must be derated according to the derating curve (Figure 1, Figure 2). The packaging we commonly refer to is the British system.

Chip resistor standard resistance

Conventional chip resistors use the E24 and E96 series. In 1948, the IEC 12th Technical Committee (Radio Communications) agreed during the Stockholm meeting that one of the most pressing issues for international standardization was the priority series for resistors and capacitors below 0.1uF.

Although it was intended to standardize these series to the 10√10 system, it was not practical to change business practices in several countries where the 12√10 system had already been adopted because the above components were standardized to allowable deviations of 5√10, 10√10 and 20√10. Although the 10√10 system was more in line with ISO practice, the committee could only regret having to recommend the 12√10 system in view of the reality. The proposal for the preferred series E6, E12 and E24 was accepted at the Paris Conference in 1950, and IEC Standard 63 (first edition) was subsequently published.