Factors Affecting LED Light Failure

LED lamps as a new type of green lighting, energy saving, environmental protection, long life, sought after by the majority of customers. However, the problem of LED light failure is also a problem that LED lamps have to face. Uninterrupted light failure has seriously affected the use of LED lamps. Today, Ming Ming Lighting (Group Enterprise) Engineering Research and Development Center summarizes several major factors that affect the LED light decay. As far as the current view is concerned, the decline of white LED in the market may be one of the most important issues for civilian lighting. What caused the LED light to fail? In general, there are two main factors for the light decay of LEDs:

First, the quality of LED products itself:

1, the LED chip used is not good, the brightness decay faster.

2. There is a defect in the production process, and the heat dissipation of the LED chip cannot be well derived from the PIN pin, resulting in an excessively high temperature of the LED chip and aggravating the attenuation of the chip.

Second, the conditions of use:

1. The LED is driven by a constant current, and some of the LEDs are driven by a voltage driver to attenuate the LED.

2, the drive current is greater than the rated drive conditions.

In fact, there are many reasons for the decline of LED products, the most critical issue is the heat, although many manufacturers do not pay special attention to the issue of heat dissipation in the secondary products, but these secondary LED products under long-term use, the degree of light failure than the focus on heat dissipation The LED product is higher. The thermal resistance of the LED chip itself, the effect of the silver paste, the heat dissipation effect of the substrate, and the colloidal and gold lines are all related to light failure. A good overall heat dissipation structure is one of the outstanding advantages of Haoming's products in the industry. The following is the patented integrated heat sink lamp of Yanming Company. The aluminum design of the whole aircraft has excellent heat dissipation performance.

Three factors that affect the quality of LED light quality degradation

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%.

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.

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.