FAQ:The Effect of Static Electricity on LED Chip( Part2 )
The effect of static electricity on LED chip causes the failure of the PN junction of LED chip, and the leakage current increases to become a resistor.
Static electricity is a ruinous evil, and the world has lost tens of millions of dollars in economic losses due to its countless electronic components.Therefore, it is an important work in the electronics industry to prevent the electronic components from static electricity damaging, and the enterprises of LED packaging and application should not be taken lightly. Any problem in the process will result in the damage to the LED, which will make the LED worse or lose efficacy. We know about the human body can carry 3 kv (ESD) static, means it can be broken down the LED chip easily. In the LED packaging production line, it is also a very important thing that the grounding resistance is in line with the requirements of all kinds of equipment, the general requirement for grounding resistance of 4Ω, somewhere requiring high its grounding resistance have to reach even two or less.
These requirements are familiar to people in the electronics industry. The key is whether or not they are in place.According to the author to know the general private enterprises, anti-static measures do not reach the designated position, the most of company cannot check the grounding resistance test records, even if the test was also once a year, or a few years time, or check the grounding resistance when have a problem. In fact, earth resistance test is a very important work, at least four times a year (once every quarter test), some require high places, will be once a month grounding resistance test.The resistance of soil will change with the seasons, spring and summer have much rain, wet soil ground resistance is easy to achieve; autumn and winter is dry, soil get water less, ground resistance is likely to exceed the prescribed value, as a record is in order to save the original data, do well documented in the future.Comply with the ISO2000 quality management system.Test grounding resistance can design forms by oneself, grounding resistance test packaging enterprises, LED applications are need to be done, as long as all sorts of equipment name fill in the table, measured grounding resistance of each equipment put on record, the tester signatures, then can be archived.
Human body electrostatic have a very big damage to the LED, while working,it should be wear anti-static clothing, equipped with electrostatic ring and static ring were good, there is a kind of electrostatic ring without need of ground, the anti-static effect is not good, do not suggest to use match this kind of product, if the staff in violation of operating procedures, he should accept the corresponding warning education, but also have the effect of notice of others.How much the body with electrostatic, would be connected to fabrics of people wear, and every man's constitution. At fall and winter night, it is easy to see discharge phenomenon in our clothes when we take off, this voltage can reach to 3 kv.
The ESD value of the silicon carbide substrate is only 1100 volts, and the sapphire substrate’s is even lower, only 500 to 600 volts. A good chip or LED, if we use hand to pick up (without any protection measures), and the clear result is, LED chip will be subject to different degrees of damage, sometimes a good device through our hands are broken, this is the electrostatic made.
Packaging companies if not according to the grounding procedures strictly, and the latter is the enterprise oneself. It will cause the loss of product qualified rate, reduce the economic benefits of enterprises, the same as application LED enterprise, if equipment and personnel without ground well, also can cause damage to the LED, rework is inevitable.In accordance with the requirements of the standard manual LED, the LED lead cable from the gel should be not less than 3-5 mm, with bent feet or welded, but most application companies do not do this, and with only separated by a piece of PCB thickness (2 mm or less) to direct welding, it can also cause damage to the LED or destroy, because the high temperature welding will affect the chip, make the chip characteristics deteriorate, reduce the luminous efficiency, even destroy the LED, those phenomenons are commonplace. Some small businesses use manual welding with 40-watt ordinary iron, the welding temperature is out-of-control, solder iron temperature is above 300-400℃, high welding temperature can cause death lamp, LED lead’s expansion coefficient at high temperature is several times than at about 150℃, the inside gold solder joints can be away the welding points because of excessive thermal expansion and contraction, then the death light phenomenon appeared.