We often encounter LEDs that don't shine. Package companies, application companies, and the units and individuals that use them are likely to come across. This is the phenomenon of dead lights in the industry. The reason is nothing more than two cases: First, the LED leakage current is too large, causing the PN junction to fail, so that the LED light does not light up, this situation generally does not affect the work of other LED lights; Second, LED lights The internal connection lead is disconnected, causing no current to pass through the LED and generating a dead light. This situation will affect the normal operation of other LED lamps, because the LED lamp has a low operating voltage (red, yellow and orange LED operating voltage is 1.8V-2.2V). , blue green white LED working voltage 2.8-3.2V), generally have to use string, parallel to connect, to adapt to different working voltage, the more LED lights in series, the greater the impact, as long as there is an LED light inside the open circuit This will cause the entire string of LEDs in the series circuit to be off, which is much more serious than the first case. LED dead lights are the key to affect product quality and reliability. How to reduce and eliminate dead lights and improve product quality and reliability is a key issue for packaging and application companies. Here are some analysis and some reasons for the cause of the dead lights.
1. damage caused by static electricity to the LED chip, the LED chip PN junction failure, leakage current increases to become a resistor
Static electricity is a very harmful devil. The world's electronic components damaged by static electricity are countless, resulting in tens of millions of dollars in economic losses. Therefore, it is an important task in the electronics industry to prevent static electricity from damaging electronic components. LED packaging and application companies should not be taken lightly. Any problem in one link will cause damage to the LED, making the LED performance deteriorate or even fail. We know that the human body (ESD) static electricity can reach about three kilovolts, which can damage the LED chip. In the LED packaging production line, the grounding resistance of all kinds of equipment meets the requirements. This is also very important. Generally, the grounding resistance is 4 Ohm, in some cases where the requirements are high, the grounding resistance should even reach ≤ 2 ohms. These requirements are familiar to people in the electronics industry. Whether the key is in place during actual execution and whether there is a record. According to the author's understanding of the general private enterprise, the anti-static measures are not in place. This is the test record that most enterprises can't find the grounding resistance. Even if the grounding resistance test is done once a year, or once a few years, or there is a problem. When checking the grounding resistance, it is a very important task to test the grounding resistance test. At least 4 times a year (tested every quarter), some places with high requirements should be grounded once a month. The soil resistance will vary with the seasons. There are many rains in spring and summer, and the soil wet grounding resistance is easy to reach. In autumn and winter, the soil moisture is less, and the grounding resistance may exceed the specified value. The record is to preserve the original data. It will be well documented in the future. Comply with ISO2000 quality management system. The test grounding resistance can be designed by itself. The grounding resistance test packaging enterprise and the LED application enterprise must do it. Just fill in the various device names in the table and measure the grounding resistance of each device. The tester's signature can be archived.
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