Analyze LED thermal indicators

1, thermal resistance Rth

The ratio of the temperature difference on the heat flow channel to the power dissipated on the channel; when the LED is illuminated to reach the heat conduction steady state, the chip surface dissipates 1 W of power, the temperature of the chip pn junction and the connected bracket or aluminum substrate The temperature difference between the temperatures is called the thermal resistance Rth in °C/W. The lower the value, the faster the heat in the sheet is transferred to the holder or aluminum substrate.

2, LED storage environment temperature and working temperature

Under normal conditions, the storage temperature of the LED should be between -40 ° C and +100 ° C. When packaging LEDs, sometimes in order to make the encapsulant or phosphor dry quickly, it can be stored at a temperature of 150 ° C for 1 to 2 hours. Whether this has an effect on the LED is yet to be verified. The operating temperature of the LED is -30 ° C ~ + 80 ° C, but the operating temperature is related to the thermal resistance. When the LED is in operation, it is best to keep its pn junction temperature below 100 °C.

3, anti-static indicators

Do a good job of LED devices to pay attention to anti-static. Static electricity may be damaged both in the transportation state and during the assembly process. Pay special attention to anti-static. After the general LED is completed, the anti-static index of the bipolar open circuit should be within 500V.

4, failure rate λ

The failure rate λ refers to how long a batch of LED devices appear after lighting, and how many 'dead lights' appear. This is a key indicator to measure the quality of these LED devices. If there is no 'dead light' phenomenon within 10 hours of operation, the failure rate is good, that is, the failure rate is 0.

5, life

Under normal operating conditions, the longer the half-light decay time of the LED device, the longer the life of the LED. According to the theoretical calculation, it can reach more than 100,000 hours. However, due to materials, manufacturing technology and Other reasons, the life of LED devices on the market can only reach 20,000 to 30,000 hours. The lifetime of the LED device is directly related to the heat dissipation conditions and light extraction efficiency of the system during use.

6, other indicators

LEDs are encapsulated by epoxy and other adhesives. Due to time and chemical action, the light transmittance of the encapsulant is deteriorated. Sometimes the gel will turn yellow and turbid, affecting light transmission; some will make the glue vitrified and broken. These will change the performance of the LED device, so it will not reach the original technical specifications, thus affecting its light extraction efficiency and service life.

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