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I believe everyone has encountered the situation of LED bead leakage in SMD, but the reasons for the leakage are different. Some SMD LED bead leakage is caused by testing after the LED bead packaging is completed, some is caused by long-term storage, some is caused by aging, and some is generated after welding. Today, let's talk in detail about the reasons for the leakage of SMD LED lamp beads?

1、 Leakage of SMD LED lamp beads caused by stress

The stress is caused by the Thermal expansion of the data. In LED beads, there are different data, and the thermal shrinkage coefficient is different. During the process of repeated temperature changes, it is impossible for each substance to return to its initial contact state, and there will be a certain amount of stress between them.

But it may not necessarily be harmful. As long as the shrinkage coefficients differ too much and the process conditions are not suitable, significant stress may be left behind. This severe stress can crush the chip, causing it to be damaged, resulting in leakage, local area cracking without brightness, or complete open circuit without brightness. When the stress is not very high, sometimes serious results can also occur.

There are already dangling bonds on the side of the SMD LED beads, and the stress causes the atoms on the surface to undergo slight displacement. The electric field of these dangling bonds becomes increasingly unbalanced, resulting in changes in the energy level state at the end PN junction and leakage.

2、 Improper use of SMD LED lamp beads to form leakage

This condition rarely occurs. When a higher reverse voltage is applied to LED beads, it may damage the PN junction and form leakage.

3、 Improper processing leads to chip cracking

The uneven gel at the bottom of the SMD LED light bead chip, or voids under the solder pad, may cause damage to the chip during wiring, resulting in leakage or failure. Improper adjustment of the soldering machine can damage the chip, resulting in leakage or failure.

4、 Electrostatic issues

The issue of static electricity cannot be ignored. Electrostatic discharge requires a conductive circuit, not to say that there is damage due to static electricity. When there is only a small amount of leakage in the LED beads, it is possible to consider the occasional damage caused by static electricity. If a large number of attacks occur, it is more likely that the chip is contaminated or stressed.

5、 Excessive silver glue leads to electric leakage and wire deviation welding leads to electric leakage

Excessive silver glue and welding deviation caused by wire leakage are common sense issues in the LED bead packaging industry

6、 Chip contaminated causing leakage

The issue of leakage caused by chip contamination is a very noteworthy one: LED chips are very small, and dust and other substances can easily cover them. The most important thing is that dust, water vapor, and various impurity ions will adhere to the surface of the chip, not only affecting the interior of the LED bead chip on the surface, but also diffusing into the interior of the LED bead chip to have an effect. For example, copper ions and sodium ions can easily diffuse into semiconductor data, and a very small amount can seriously deteriorate the performance of semiconductor devices.