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What is the number of LED dead light in the end?(III)
- May 25, 2017 -

4. Silver peeling

Conductive silver plastic matrix is epoxy resin materials, thermal expansion coefficient than the chip and the bracket are much larger in the lamp beads of hot and cold impact of the use of the environment, because of heat problems stress, the temperature changes in the environment will be more intense To intensify, the colloid itself has tensile breaking strength and ductility, when the tension is over, then the colloid is cracked. Solid crystal glue at the interface of the peel, the heat drastically worse, the chip can not be derived from the heat, the junction temperature increased rapidly, greatly accelerated the process of light failure.

15. Silver paste

Silver powder particles dispersed in the suspension system in the slurry system, silver powder and the matrix due to the density difference, charge, cohesion, the force and the structure of the dispersion and many other factors, often appear silver deposition stratification phenomenon, if the sedimentation Fast will make the product in the hanging pulp when the sagging, coating thickness is not uniform, and even affect the physical and chemical properties of the coating, stratification will also affect the device heat, bonding strength and conductivity.

16. Silver ion migration

A customer with silicone packaging, conductive silver glue bonded vertical flip light source leakage phenomenon, commissioned Jin Jian find the cause. According to the analysis of the bad lamp beads, abnormal silver elements were detected on the side of the chip, and it was observed that the silver particles gradually spread from the bottom positive silver colloidal area to the dendritic extension morphology to the vicinity of the P-N junction side of the upper part of the chip. It is very likely that the silver ions from the solid crystal silver glue are caused by ion transport on the side of the chip. The phenomenon of silver ion migration is gradually formed in the process of product use. With the increase of migration phenomenon, the final silver ion will turn on the chip P-N junction, resulting in the existence of low resistance path on the chip side, resulting in abnormal leakage current Even in the case of short circuit caused by the chip. The reason for the migration of silver is multifaceted, but the main reason is that the silver-based material is damp, and after the silver paste is damped, the intruding water molecules make the silver ionized and migrate along the chip side in the vertical direction. Therefore, the proposed inspection of customers with caution silicone packaging, silver glue bonded vertical flip chip beads, the use of gold and tin eutectic welding method will be fixed on the bracket in the chip, and to strengthen the waterproof characteristics of lamps and lanterns detection.

17. Solid crystal stickers do not dry

The encapsulant for silicone encapsulation contains a platinum (platinum) complex, which is very susceptible to poisoning. The toxicant is any of a nitrogen (N), phosphorus (P), sulfur (S) Compounds, once the curing agent poisoning, organic silicon curing is not complete, it will cause the linear expansion coefficient is high, the stress increases.

Packaging glue

18. Glue heat resistance is poor

According to our tests show that pure silica gel to 400 degrees began to crack, but added epoxy resin modified silicone heat resistance was pulled down to the level of epoxy resin, when the modified silica gel applied to high-power LED Or high temperature environment, there will be colloidal yellow hair black burst death lights and so on.

19. Glue dry

The encapsulant for silicone encapsulation contains a platinum (platinum) complex, which is very susceptible to poisoning. The toxicant is any of a nitrogen (N), phosphorus (P), sulfur (S) Compounds, once the curing agent poisoning, organic silicon curing is not complete, it will cause the linear expansion coefficient is high, the stress increases.

Such as Sn, Pb, Hg, Sb, Bi, As and other heavy metal ion compounds; containing ethynyl and other unsaturated groups of organic compounds; organic compounds containing N, P, S and other organic compounds; Note the following:

Organic rubber: Sulfur vulcanized rubber such as gloves

Epoxy Resin, Polyurethane Resin: Amine, Isocyanate Curing Agent

Integrated silicone RTV rubber: especially the use of Sn-like catalyst

Soft cyanide: plasticizer, stabilizer

Flux

Engineering plastics: flame retardants, enhanced heat resistance, UV absorbers and so on

Silver plating, gold-plated surface (the plating solution is the main reason)

Solder register degassing (caused by silicone heat curing)

20. Package glue line expansion coefficient is too large

In the use of cold and cold impact of the lamp in the environment, because of heat problems stress, the temperature changes in the environment will be more aggravated effect, the colloid itself has tensile strength and elongation, when the tension is over, then the colloid Cracked out.

21. Glue with chlorine

However, the current domestic production of epoxy resin production enterprises generally small, management and production process backward, the operating machinery is not high degree of automation, leading to the parameters of epoxy resin is difficult to protect. Low-quality production of epoxy resin and the status quo of China's current industry-related industries need to upgrade.

The chlorine in the epoxy resin not only scours the stencil plating layer, alloy wire or other active metal and chip electrode (aluminum reflective layer), but also can react with the amine curing agent to affect the curing of the resin. Chlorine content is an important physical index of epoxy resin, it refers to the epoxy resin contained in the mass fraction of chlorine, including organic chlorine and inorganic chlorine. Inorganic chlorine affects the electrical properties of the cured resin. The organochlorine content indicates the fraction of the chlorolauryl group in the molecule that does not undergo a closed loop reaction, and its content should be reduced as much as possible, otherwise it will affect the curing of the resin and the properties of the cured product.

In order to more efficient anti-electrode chlorine corrosion phenomenon, reduce the quality of the industry's risk, the world's exclusive to the LED manufacturers to launch "Kam Kam chlorine-free certification" testing services. "Kam Kam chlorine-free certification" is designed to confirm whether the LED glue and the chip contains excessive chlorine, detection accuracy to PPM level. The contents of the certification report can be found on the website. Gmatg. Com query. With the "Kam Kam chlorine-free certification" service, LED buyers can rest assured that the procurement of "Kam Kam chlorine-free certification," the raw materials, greatly reducing the risk of raw material procurement.

Gold Line

22. Copper alloy, gold alloy silver alloy wire, silver alloy wire instead of gold wire

Gold wire has the advantages of high conductivity, good thermal conductivity, corrosion resistance, good toughness, excellent chemical stability, etc., but the expensive gold line, resulting in packaging costs are too high. In the periodic table, the transition metal elements in gold, silver, copper and aluminum four kinds of metal elements with high conductivity. Many LED manufacturers trying to develop such as copper alloy, gold alloy silver alloy line, silver alloy wire to replace the expensive gold line. Although these alternatives are superior to gold wires in some properties, they are much worse in terms of chemical stability, such as silver and gold-clad silver alloy lines susceptible to sulfur / chlorine / bromide corrosion, and copper wires are susceptible to oxidation. In the case of encapsulated silica gel similar to that of a water-absorbing sponge, these alternatives make the bonding wire susceptible to chemical corrosion, the reliability of the light source is reduced, the use time is long, and the LED lamp beads are easily broken.

23. Diameter deviation

1 gram of gold, you can pull out the length of 26.37m, diameter 50μm (2 mil) of the gold line, you can also pull the length of 105.49m, diameter 25μm (1 mil) gold wire. If the length of the gold line is fixed, if the diameter of the incoming gold wire for the original half, then hit the gold line measured resistance is a normal quarter.

Jin Jian detection pointed out that for the supplier, the finer the smaller the diameter, the lower the cost, in the case of the same price, the higher the profits. For the use of gold wire LED customers, the procurement diameter cut corners of the gold line, there will be gold wire resistance increases, the risk of reducing the current fuse will greatly reduce the life of LED light source. 1.0 mil gold line life, must be shorter than the 1.2 mil gold line, but the packaging plant is a simple test is not out, in this Kam Kam can provide gold wire diameter of the incoming detection.

24. Surface defects

(1) The surface of the wire shall be free of defects such as 5% of the diameter of the wire, pits, scratches, cracks, bumps, discounts and other defects in the service life of the device. Gold wire in the drawing process, the surface of the wire surface defects, will lead to increased current density, so that damage to the site easily burned, while reducing the ability to resist mechanical stress, resulting in damage to the inner lead fracture.

(2) gold wire surface should be no oil, rust, dust and other adhesives, which will reduce the gold line and LED chip between the gold line and the bonding strength between the bracket.

25. Pull-off load and elongation are too low

The good gold wire that can withstand the impact of the resin package must have the specified pull-off load and elongation. At the same time, the breaking force and elongation of the gold wire play a key role in the quality of the wire bonding, and the bonding wire having a high breaking rate and elongation is more advantageous for bonding. Too soft gold will lead to the following bad: (1) arch wire drooping; (2) spherical instability; (3) the ball neck easily shrink; (4) gold line easy to break. Too hard gold wire will lead to the following bad: (1) the chip electrode or epitaxial play hole; (2) gold ball neck fracture; (3) the formation of alloy difficult; (4) arch wire arc control difficult.

Conclusion

After enumerating so many reasons, we can sum up the conclusion, a simple die of LED die, it may be dozens of reasons caused by the same reason, the past LED industry problems encountered after most Mongolian and guess, can not see the nature of the problem , Fundamentally solve the problem, Jin Jian, such as LED material testing company focused on a lot of experience theory, through the division of labor from different professional team, high-precision testing equipment, set the industry failure case based on large data , To arrive at more precise conclusions.

 

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