This rapid aging test method LED applications can try!

[LED] - Abstract: Based on five principles and five LED packaging material process, analysis of the main factors affecting the life of LED, with high temperature and high current test conditions of rapid aging fast analysis LED screening test. For the rapid introduction of LED manufacturers do.

Keywords: LED packaging materials, rapid aging

Introduction

With the continuous development of LED products, LED industry, whether from the upstream chip, the middle reaches of the packaging or downstream applications are showing a hundred flowers. However, it is now from the state of letting a hundred flowers bloom to the pattern of the development of the big reshuffle, how to survive in the big reshuffle in LED, the biggest factor is to improve the cost of their products. Therefore, the current LED industry, whether it is PHILPS, OSRAM and other LED giants or some small-scale domestic companies are in the brutal price war. For LED lighting products, LED particle costs accounted for the highest proportion, so the application of LED factory will keep looking for suppliers of low-cost LED particles, LED particles and suppliers to make their products more cost-effective to have to do this fall. Therefore, LED chips, gold, stents and other raw materials are the first to be replaced.

For now, the price of LED particles down the frequency has dropped from the previous quarter to improve the monthly drop this, so how to do a good job of LED trust is critical. If the LM 80/LM 79 test can not meet the application requirements of the factory, LM 80 of the normal test cycle is 6000hr, according to the verification of this way after the completion of LED grain price has been done several times updated. So for LED applications, it is necessary to make a judgment in a short period of time on the reliability of a LED, that is, a low-cost, rapid and effective method for screening LED particles.

LED packaging material introduction

As shown in Figure 1 (), the main raw materials of the LED include packaging adhesive, gold wire, chip, solid crystal glue, and bracket. Each material will directly affect the performance of LED. For example, poor packaging will not only lead to low light efficiency, but also lead to easy to damp material, vulcanization risk increases.

With more and more LED packaging companies, under the pressure of competition and the elimination of the cost, packaging factory use wire has been from the beginning of the 99.99% pure gold K into gold, palladium plating copper wire, and the thermal conductivity will decrease, but the ductility decreases, so for the outside world to produce stress will be very sensitive, very easily broken, for example, because the LED for moisture sensitive devices, if LED has the water vapor into, when after the completion of a patch reflow will stress due to thermal expansion, if the wire is not good ductility due to stress will easily lead to breakage, resulting in dead lights after reflow phenomenon is serious.

Also under the pressure of the cost, many packaging factory is in reducing the size of the wafer, and over current operation such as the early 10*30mil chip will only do 0.1W, drive to 30mA, and now some manufacturers will overload to 100mA, it has exceeded the maximum withstand current of the wafer, the risk of failure is too big light.

Another important material which has a great influence on the life of LED is the scaffold. As a LED, in the premise of constant cost, to obtain a more luminous flux, the most effective way is to drive current, but this operation will cause the current density is too large, resulting in the increase of heat is very large, as shown in Figure 2 with a 2835 1W LED candle lamp push the temperature corresponding to different current.

Figure 2 LED different driving current corresponding temperature (test instrument: infrared thermal imager)

As can be seen from the figure, LED drive current decreased by 20%, corresponding to the LED chip surface temperature decreased by 17%. Another 130 degrees has exceeded the maximum temperature of the LED chip (generally small and medium power chip is 115 degrees, a good point of the order of 125 degrees). High temperature not only leads to LED chip damage, phosphor excitation efficiency, also can make the reflection on the bracket cover to yellow, will eventually lead to serious LED decay.

Currently small and medium power (0.5W) or the use of PA9T, some manufacturers even for the consideration of the cost of the use of PA6T, high temperature resistant. For the best performance in terms of EMC, followed by PCT, and then PA9T, PT6T worst performance.

Discussion on the method of rapid aging of LED

This paper discusses application of LED plant LED particles fast aging test method based on LED application, when the factory got LED packaging factory to provide samples, divided into three parts: 1. The initial screening test for photoelectric parameter testing of LED particles, including photoelectric parameters under different parameters, such as chip size; the rapid aging at room temperature, 1.5 test. The.85 times the current; C, the rapid aging current nominal test. The following is illustrated with a practical case.

One caveat: the rapid aging test to estimate life only for reference, there is not a fast aging test standard, so this method is only used as a lighting factory under the same experimental conditions LED particles suppliers compared test, select the reference.

Initial photoelectric parameter measurement and chip size measurement

The initial parameter test of A, B two LED particles, the test results are shown in Table 1, can be seen from the table A, B two material initial flux is equivalent to that of the B manufacturers is low voltage, the overall optical efficiency will be higher than the A manufacturers.

Table 1 A, B two LED particle initial photoelectric parameters

2D chip from the figure can be seen using A chip size is greater than B manufacturers, A chip manufacturers