Brief description of factors affecting LED light decay

As a new type of green lighting, LED lamps are energy-saving, environmentally friendly and have a long lifespan, and are highly sought after by customers. However, the problem of LED light decay is another problem that LED lamps have to face. Continuous light decay seriously affects the use of LED lamps.

At present, the light decay of white light LEDs on the market may be one of the primary issues for civilian lighting. What causes the light decay of LEDs? Generally speaking, there are two main factors for the light decay of LEDs:

1. Quality issues of LED products themselves:

1. The LED chip used is of poor quality and the brightness decays quickly.

2. There are defects in the production process. The heat dissipation of the LED chip cannot be well conducted from the PIN pin, resulting in the LED chip temperature being too high and the chip attenuation being aggravated.

2. Conditions of use:

1. LED is driven by constant current, and some LEDs are driven by voltage, which causes the LED to attenuate.

2. The driving current is greater than the rated driving condition.

In fact, there are many reasons for the light decay of LED products, the most critical one is the heat problem. Although many manufacturers do not pay special attention to the heat dissipation problem in secondary products, the light decay of these secondary LED products will be higher than that of LED products that pay attention to heat dissipation after long-term use. The thermal resistance of the LED chip itself, the influence of silver glue, the heat dissipation effect of the substrate, as well as the colloid and gold wire are also related to the light decay.

Three factors that affect the quality and light decay of LED lamps

First, choose what kind of LED white light.

This is very important. The quality of LED white light can be said to be a very important factor. For example, taking the same Jingyuan 14mil white light segment chip as a representative, the LED white light encapsulated with ordinary epoxy resin base glue, white light glue and encapsulation glue, a single LED is lit in an environment of 30 degrees. After one thousand hours, the attenuation data is 70%; if it is encapsulated with Class D low-attenuation glue, under the same aging environment, the light attenuation after one thousand hours is 45%; if it is encapsulated with Class C low-attenuation glue, under the same aging environment, the light attenuation after one thousand hours is 12%; if it is encapsulated with Class B low-attenuation glue, under the same aging environment, the light attenuation after one thousand hours is -3%; if it is encapsulated with Class A low-attenuation glue, under the same aging environment, the light attenuation after one thousand hours is -6%.

Secondly, the working environment temperature of LED lamp beads.

According to the data of single LED white lamp aging, if only one LED white lamp is lit and the ambient temperature is 30 degrees, then the bracket temperature of the single LED white lamp will not exceed 45 degrees. At this time, the life of this LED will be ideal.

If 100 LED white lights are lit at the same time, and the interval between them is only 11.4mm, then the temperature of the brackets of the LED white lights around the light stack may not exceed 45 degrees, but the LED white lights in the middle of the light stack may reach a high temperature of 65 degrees. At this time, it is a test for the LED lamp beads. Then, in theory, the light decay of the LED white lights in the middle will be faster, while the light decay of the LED white lights around the light stack will be slower.

Anyway, everyone should know that LEDs are afraid of heat. The higher the temperature, the shorter the LED life, and the lower the temperature, the longer the LED life. The ideal operating temperature of LED is of course between minus 5 and zero degrees. But this is basically impossible.

Therefore, after we understand the ideal working parameters of LED lamp beads, we try to enhance the heat conduction and heat dissipation functions when designing lamps. Anyway, the lower the temperature, the longer the LED life.

Again, the working electrical parameters of LED lamp beads are designed.

According to the experimental results, the lower the driving current of the LED white light, the less heat it emits, and of course, the lower the brightness. According to the survey, in the design of LED solar lighting circuits, the driving current of the LED is generally only 5-10mA; for products with a large number of lamp beads, such as more than 500 or more, the driving current is generally only 10-15mA, and the driving current of general popular LED lighting applications is only 15-18mA, and very few people design the current to be more than 20mA.

The experimental results also show that under a driving current of 14mA, with a cover to prevent ventilation and an air temperature of 71 degrees inside, the low-fading product has a zero light decay after 1,000 hours and a 3% light decay after 2,000 hours. This means that this low-fading LED white light has reached its maximum limit in such an environment, and any greater limit would be a damage to it.

Because the aging board used for aging has no heat dissipation function, the heat generated by the LED when it is working basically cannot be conducted to the outside. This has been proved in the experiment. The air temperature inside the aging board has reached a high temperature of 101 degrees, and the surface temperature of the cover on the aging board is only 53 degrees, which is a difference of dozens of degrees. This shows that the designed plastic cover basically has no heat conduction and heat dissipation function. However, in general lamp design, the function of heat conduction and heat dissipation is taken into consideration. Therefore, in summary, the design of the working electrical parameters of the LED lamp beads should be based on the actual situation. If the heat conduction and heat dissipation function of the lamp is very good, it does not matter if the driving current of the LED white lamp is increased a little, because the heat generated by the LED lamp beads can be instantly exported to the outside, without damaging the LED, which is the best care for the LED. On the contrary, if the heat conduction and heat dissipation function of the lamp is so-so, it is best to design the circuit to be smaller so that it can release less heat.