LED package temperature distribution analysis

As the fourth-generation light-emitting diode (LED), it has received more and more attention for its energy saving, environmental protection, small size, long life and fast response. However, the photoelectric conversion efficiency of LEDs is not high, only about 30% of the electrical energy is converted into light energy, and the remaining 70% is converted into thermal energy. Excessive heat causes the LED junction temperature to rise, resulting in a decrease in the operating voltage of the chip, a decrease in light intensity, a longer wavelength of light, an increase in light decay, and the like, which seriously affects the life of the LED. Therefore, reasonable thermal design is a key factor to ensure the normal operation of LEDs.

The main factors affecting the temperature distribution of LED package devices are: chip heating power, solid crystal rubber thermal resistance, and bracket thermal resistance. This paper will analyze the effects of the above three factors on the temperature distribution of each part of the LED package.

Second, build a model

In order to reduce the modeling time, this paper only changes the thermal conductivity of each part to change its heat conduction. Figure 1 shows a three-dimensional schematic of the analytical model. The selected LED model is the common 3528, mounted on a hexagonal aluminum plate (MCPCB), and the gold wire is ignored in the model. The red temperature follow-up temperature pick-up curve on the right is the main heat flow channel of the LED package: chip-solid glue-bracket.

Model parameter setting:

1. The chip is loaded with uniform volumetric thermal power,

2. Ambient temperature: 30DegC;

3. Material thermal conductivity is shown in Table 1.

Third, experimental design and simulation

In this paper, the simulation method will be used to simulate the change of the thermal resistance of the solid crystal glue, the thermal resistance of the bracket, and the temperature distribution of the LED package after the chip heating power.

1. The effect of the change of thermal conductivity of solid crystal glue on the temperature distribution of LED. The thermal conductivity of solid crystal adhesive is set to 0.2, 0.5, 0.8 (W/Mk) respectively. The thermal conductivity of the copper substrate of the bracket is set to 294w/mk, and the chip power is 0.064. W, other conditions remain unchanged.