LED lamps life and color keeping degree index, from the current view is very high, in fact many LED lamps still short of this request, because LED flashlight technology involved a lot of problems, very complex, which is mainly system reliability problems, including LED chips, sealing device, drive the power modules, heat and the reliability of the lamps. To have good mechanical properties and sealing, cooling the body and dustproof, LED the rise of temperature of the lamps shall be required little 30 ℃. LED flashlight in addition to improve the design efficiency with light requirements, lamps, appearance beautiful besides, to increase the cooling level, the heat conduction good material, there are reports that, cooling the body with some materials, the thermal conductivity increases by 30%. The following respectively for the problems analysis:
On the analysis of the reliability LED lamps, before the reliability of the basic content of LED some introduction, the reliability of the lamps of LED deep analysis of the help. Nature failure, affiliate failure: LED devices are generally classified into two failures: nature and affiliate failure. Nature means LED chips failure caused by failure, and divided into electric drift and ion thermal diffusion failure. Affiliate failure is general by package structure material, process cause, namely the package structure and use of epoxy, silica gel, conductive rubber, phosphor, welding, lead, process, temperature, etc reasons.
Ten degrees law: some electronic device in certain temperature range, every 10 ℃ temperature rise, the main technical indexes down half (or down a quarter). Practice has proved, LED device heat sink in 50 ℃ temperature to 80 ℃, LED life value with the basic law of ten degrees. Also recently media reports: LED every rise by 2 ℃ temperature devices, its life fell by 10%, when the temperature from 63 ℃ to 74 ℃} rise, average life expectancy down three quarters. Because different device packaging technology, complete the case.
The meaning of life: life is to point to in provisions LED working conditions, the light output power or flux attenuation to the initial value of 70% of working time, at the same time, keep the change in 0.007 in color; Life expectancy is the significance of LED products before failure LED the working time of the average, with MTTF to say, it is the most commonly used electronic device reliability parameters. We have discussed here just life test, other projects are not considered.
Long life test: in order to confirm whether life LED flash lights to 35000 hours, requires a long life test, the current practice of basically form below consensus: because the LED device GAN began optical power output is not stable, so the United States ASSIST by league rules, the need for electricity is aging 1000 hours, the measurement of optical power or flux for the initial value. After 3000 hours and rated current, measuring LED luminous flux (or optical power) attenuation to less than 4%, plus current 3000 hours, flux attenuation to less than 8%, again electrify 4000 hours, a total of 10000 hours, the flux attenuation to less than 14%, namely the flux of the initial value to more than 86%. At this time to prove to ensure that LED to life 35000 hours.
Accelerate (short term) life test: electronic devices can be accelerated life tests in increasing stress (power or temperature) tested under, here to discuss the temperature stress is the way, measuring the calculated life is LED average life expectancy, namely the failure of the average working hours before. Using this method will greatly shorten the service life of the test time flashlights with high lumens , to prompt improvement, improve reliability of LED flashlight.
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