Factors that affect the light decay of LED lamps

The data detected by the single LED white light on the burn-in board and the data detected when the LED white light is assembled into a lamp when it is aging is definitely a bit different.

The size of this difference depends on the electrical parameters of the LED during operation and the design of the luminaire, as well as the environment in which the luminaire is used.

First, what kind of LED white light is selected.

This is very important. The quality of the LED white light can be said to be an important factor. To give some examples, the same as the 14mil white light segment chip as the representative, with the ordinary epoxy resin primer and white glue and encapsulation glue LED white light, single lit in a 30-degree environment, a After 1000 hours, the attenuation data is 70% of light decay; if packaged in Class D low-fat glue, the 1000-hour light decay is 45% under the same aging environment; if the C-type low-failure glue is encapsulated, the same aging environment , 1000 hours light decay is 12%; if the class B low-failure glue encapsulates, in the same aging environment, the 1000-hour light decay is -3%; if the class A low-fade glue, in the same aging environment, the thousands of hours light The decline is -6%.

Why do different packaging processes lead to big differences?

The main reason is that LED chips are afraid of heat. Occasionally overheating more than a hundred degrees in a short period of time, it does not matter, afraid of fear of long-term high temperature, is a great damage to the LED chip.

In general, the thermal conductivity of ordinary epoxy resin is very small, so when the LED chip is lit, the LED chip will emit heat, while the ordinary epoxy thermal conductivity is limited, so when you from the LED white light When the external temperature of the LED support is measured at 45 degrees, the center temperature of the chip inside the LED white light may exceed 80 degrees. The temperature node of the LED is actually 80 degrees, then, when the LED chip works in the temperature-saving temperature, it is very much suffered, which accelerates the aging of the LED white light.

When the LED chip is in operation, the center temperature produces a high temperature of 100 degrees, and it can instantly derive heat through 98% of the bracket pins, thereby reducing the heat damage to it. Therefore, when the temperature of the LED white light holder is 60 degrees, the center temperature of the chip may be only 61 degrees.

From the above data, it can be seen that what kind of packaging process LED white light directly determines the light failure of the LED lamp.

Second, the operating temperature of the LED lamp beads.

According to the aging data of a single LED, if there is only one lighting job for the LED white light and the ambient temperature is 30 degrees, the bracket temperature of the single LED white light will not work. More than 45 degrees. At this time, the life of this LED will be ideal.

If there are 100 LED white lights working at the same time, and the interval between them is only 11.4mm, then the temperature of the LED white light bracket around the light stack may not exceed 45 degrees, but the middle of the light Those LED white lights may reach a high temperature of 65 degrees. This time, the LED lamp beads is a test. Then, those LED white lights gathered in the middle, in theory, light decay will be faster, and the LED white light around the lamp, the light will be slower.

However, if the LED lamp beads are separated by more than 25 mm, then the heat that they diverge from each other will not accumulate. At this time, the temperature of each LED white lamp holder should be less than 50 degrees, which is more conducive to the normal operation of the LED.

If the working environment of the LED is in a relatively cold place, the average temperature of the whole year may be only about 15 degrees, or less, and the life span of the LED is longer.

Or, when the LED is working, there is a small fan blowing next to help it to dispel heat, so this is also very helpful for the life of the LED.

In any case, we should know that the LED is afraid of heat, the higher the temperature, the shorter the LED life, the lower the temperature, the longer the LED life. The ideal operating temperature of the LED is of course between minus 5 and zero degrees. But this is basically impossible.

Therefore, after learning about the ideal operating parameters of the LED lamp beads, we will strengthen the heat conduction and heat dissipation functions as much as possible when designing the lamps. The lower the temperature anyway, the longer the LED lifetime.

Again, the operating parameters of the LED lamp beads are designed.

According to the experimental results, the lower the driving current of the LED white light is, the smaller the emitted heat is. Of course, the brightness is smaller. According to the survey, LED solar lighting circuit design, LED drive current is generally only 5-10mA; lamps used in a large number of lamp beads, such as more than 500, or more, the drive current is generally only 10-15mA , And the general popularity of LED application lighting drive current is only 15-18mA, few people design the current to more than 20mA.

The experimental results also show that under the 14mA driving current, and the lid is not airtight, the inside air temperature reaches 71 degrees, low-failure products, zero-hour light decay is zero, 2000 hours light decay is 3% This shows that this kind of low-fat LED white light has reached its maximum use in such an environment, and even greater is a damage to it.

Because the aging board used for aging has no heat dissipation function, the heat generated when the LED is working is basically impossible to conduct outside. This is experimentally proven. The air temperature inside the aging board has reached a high temperature of 101 degrees, and the cover surface temperature of the aging board is only 53 degrees, a difference of several tens of degrees. This shows that the design of this plastic lid basically does not have a thermal conduction heat dissipation function. However, in the general lighting design, the function of heat conduction and heat dissipation is taken into consideration. Therefore, in summary, the design of the LED lamp beads operating electrical parameters should be based on the actual situation, if the thermal conductivity of the lamp is very good, the LED white lamp drive current is increased a little, it does not matter, because the LED lamp beads work The heat can be exported to the outside instantly, no damage to the LED, is the best care for the LED. On the other hand, if the luminaire's thermal conductivity is so-so, it's best to design the circuit a bit smaller so that it can put less calories out.