The invalidation cause of LED light source module
the LED light source module generally consists of substrate, chips, packaging materials (
, lens, some modules include radiator and thermal conductive silicone, popular now with DOB and COB packaging way.
Because the LED light source module design of diversity and complexity, so the cause of failure is also very much, generally includes the following: 1.
LED encapsulation material degradation in the daily life in the process of using, the LED to work for a long period of time the radiative recombination between blu-ray and GaN system of belt produced by the ultraviolet radiation and temperature rise caused by the appearance of the LED packaging materials (
Such as epoxy resin)
In many of the polymer optical transparency of drop considerably, thus caused the LED light efficiency decline.
Pollutants welding LED pollutants refers to the LED in the process of packaging, LED chip electrode by droplets, covered with oil, fiber, dust and other material pollution, lead to the LED solder joint part or all of the defects of poor contact and form, this is one of the largest LED welding defect damage.
According to the experimental results show that when the pollutants covering the whole of the solder joint, the welding place to form the metal -
Metal structure, also known as the tunnel junction.
And in the process of the luminous device, as a result of the existence of tunnel junction, the peak wavelength of the luminous intensity of LED chips will be reduced to 60% of normal.
Therefore, the reliability of LED encapsulation weld defects detection is very necessary.
Solid crystal glue caused by failure in the white LED industry often use solid crystal glue aerobic resin insulating rubber, silicone resin insulated, silver glue, each have advantages and disadvantages, and three in consideration when you choose.
Epoxy resin: insulated thermal conductivity is poor, but high brightness;
Insulation: silicon resin glue thermal effect is better than epoxy resin, high brightness, but as a result of silicon components occupy a certain proportion, solid crystal were beside the residual silicon resin combined with fluorescence epoxy resin in the adhesive interlayer phenomenon, can be created after cold and hot shock will generate stripping cause death light;
The thermal conductivity of the silver glue is better than both before, can prolong the service life of the LED chip, but silver light absorption is bigger, leading to low brightness.
For double electrodes when used in silver glue crystal blue chip to control the amount of also is very strict, otherwise easy to generate short circuit, directly affect the yield of product.
For different types of device products, therefore, to properly choose different solid crystal glue, so they can better reduce failure caused by the device.
Phosphor failure to realize there are many types of white LED the way, at present, the most commonly used, is one of the most mature by the LED chip produced by the blue light yellow phosphor, so the material of phosphor for white LED attenuation effect.
Phosphor's own quality of normal LED light-emitting life has very important influence.
Heat dissipation problems caused by the failure of LED is a solid-state semiconductor devices, and the LED chip's surface area is lesser, working current density is big, and often require multiple leds when used for lighting.
LED intensity big, cause the chip fever density is high, the light output and junction temperature increase, decrease, chip speed reduced, shorten the device lifetime.
If you want to consider the practical application of color drift effects, thermal design is the highest and calibrate restrictions.
Due to the continuous improvement of LED chip, the input power, the power type LED packaging technology is put forward higher requirements, now the cooling problem has become the key factor restricting the development of high power LED.
LEDGaN epitaxial material defect caused by failure because there is no match with GaN substrate material, GaN in the vast majority of the LED devices are currently there are lots of defects in thin film.
GaN material with the current mainstream of substrate sapphire crystal lattice constant mismatch at a rate of 14%, and the growth of GaN on sapphire substrate material of dislocation density is 108 / cm3 ~ 1010 / cm3.
In the process of preparing leds, the defects of material has the adsorption on the carrier, which formed in the active layer radiationless recombination center, increased the absorption of light, LED to a decline in LED luminous efficiency;
Occurs when the current is large enough, carrier radiation compound, but it will cause the lattice vibration, accelerating the formation of the defects of lattice thermal games, LED the heterojunction degradation.
Components in contact with the metal electrodes in the electric stress and thermal stress under the action of will along the dislocation migration, thus forming a low-pass ohm resistance, it will lead to falling light power device and an increase in leakage current.
Therefore, improve the quality of the epitaxial material, reduce the defect density in the material can effectively improve the reliability of the LED device.
Electrostatic damage caused by the failure of GaN material has 3.
39 ev wide bandgap, high resistivity.
Therefore, GaN LED chips in the process of its production, transport produced by the accumulation of electrostatic charge is easy to produce high electrostatic voltage.
GaN of the sapphire substrate LED device structure of electrostatic capacity is very small, vulnerable to the electrostatic breakdown.
Under the condition of the static electricity protection, produced by the human body electrostatic local breakdown easy to LED, the LED device is electrostatic breakdown will cause permanent failure.
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