Detailed explanation of temperature rise calculation of chip resistors

In the design and manufacturing process of electronic products,Chip resistorAs a common electronic component, its performance and stability directly affect the reliability of the entire circuit. Temperature rise refers toresistanceThe phenomenon that the heat generated by the passage of electric current during operation causes its own temperature to rise. Reasonable calculation of the temperature rise of chip resistors can help ensure that the resistors operate within a safe temperature range and avoid performance degradation or damage caused by overheating. This article will introduce in detail the calculation method of chip resistor temperature rise and related influencing factors to help engineers better design and selection.

1. Basic concepts of temperature rise of chip resistors

Temperature rise (ΔT) refers to the increase in the temperature of the chip resistor relative to the ambient temperature when it is working. The size of the temperature rise depends on the power consumption of the resistor and its heat dissipation conditions. Excessive temperature rise may cause resistor value drift, thermal failure or even burnout, so accurate calculation of temperature rise is crucial to ensure circuit stability.

2. Calculation of chip resistor power loss

The power loss P of the chip resistor can be calculated by the formula P=I²R or P=U²/R, where I is the current, U is the voltage through the resistor, and R is the resistor resistance. Power loss is the fundamental cause of temperature rise, and reasonable assessment of power loss is the first step in temperature rise calculation.

3. Thermal resistance parameters and their significance

Thermal resistance (θ) is an important parameter to measure the heat dissipation ability of a resistor, and its unit is °C/W. The thermal resistance of chip resistors includes junction to case thermal resistance (θJC), case to environment thermal resistance (θCA), etc. The total thermal resistance determines the temperature rise under unit power, and the temperature rise calculation formula is ΔT = P × θ.

4. Effect of ambient temperature on temperature rise

The ambient temperature (Ta) is the reference temperature when the resistor is working. Under the same power, the higher the ambient temperature, the higher the working temperature of the resistor. The maximum ambient temperature needs to be considered during design to ensure that the resistor temperature does not exceed its rated limits.

5. Heat dissipation conditions and heat dissipation methods

The heat dissipation methods of chip resistors mainly include natural convection, radiation and heat conduction through PCB. PCB material, copper foil area and layout will all affect the heat dissipation effect. Optimizing PCB design, such as increasing the copper foil area and thickening the copper layer, can effectively reduce temperature rise.

6. Calculation formula and examples of temperature rise

The commonly used temperature rise calculation formula is:

ΔT = P × (θJC + θCA)

For example, a chip resistor with a resistance of 100Ω and a current of 0.05A has a power P=I²R=0.05²×100=0.25W. Assuming that the total thermal resistance is 100°C/W, the temperature rise ΔT=0.25×100=25°C. If the ambient temperature is 40°C, the resistor operating temperature is 65°C.

7. Effect of temperature rise on chip resistor performance

Excessive temperature rise will cause the resistance value of the resistor to change and affect circuit performance; in severe cases, it may also cause the resistance material to age or even fail. Therefore, the design should ensure that the temperature rise is within a safe range and select appropriate power levels and heat dissipation measures.

8. Test method for temperature rise of chip resistor

The actual temperature rise measurement can be completed by thermocouples, infrared thermometers and other means. During the test, the surface temperature of the resistor needs to be measured under stable working conditions and compared with the ambient temperature to verify the accuracy of the calculation results.

9. How to reduce the temperature rise of chip resistors

Reasonable selection of resistor power levels, optimized circuit design, increasing heat dissipation area, using high thermal conductivity materials and improving air circulation conditions are all effective measures to reduce temperature rise. All factors should be considered comprehensively during design to ensure safe and stable operation of the resistor.

The temperature rise calculation of chip resistors is an important part of electronic design, involving many factors such as power loss, thermal resistance parameters, ambient temperature and heat dissipation conditions. Accurate calculation and reasonable control of temperature rise can not only extend the life of the resistor, but also improve the reliability and stability of the entire electronic product. Through the introduction of this article, engineers can more scientifically evaluate the temperature rise of chip resistors, optimize design solutions, and ensure the safe operation of electronic equipment.