1 Overview
With the continuous improvement of LED light efficiency in recent years, the life and reliability of LEDs have received more and more attention from the industry. It is one of the most important performances of LED products . Lifetime is the ultimate performance of reliability. However, the theoretical life of LED is very long. Like the traditional light source, the cycle test of 2h45min and 15min is used to end the life. The measurement of LED products is obviously unrealistic. Therefore, it is necessary to adopt accelerated aging life test for LED products [1]. At the same time, it should also test the thermal properties, environmental weather resistance, electromagnetic compatibility immunity and other properties closely related to life and reliability, in order to comprehensively analyze LED. life.
2, LED reliability and life-related key indicators
Every component and link in the manufacture of LED products has an impact on its reliability and lifetime, such as the solder joints of LED junctions and substrates, the thermal quenching and degradation of LED phosphors, the degradation of packaging materials, and the failure of drivers. The final possibility of degradation is the semiconductor (PN junction) itself. These factors lead to LED product failure (degeneration) in different ways, generally can be divided into gradual degradation (gradual degradation) and transient degradation (abrupt degradation).
LED's graded degradation (failure) indicators mainly include:
The lumen maintenance rate decreases, that is, the light decay, generally with an initial luminous flux of 100%. When the lumen maintenance rate of the LED product drops to 70% or 50% of the initial value, the LED is considered to be ineffective, and the lumen maintenance life is correspondingly recorded as L50 or L70;
Color drift, subject to changes in phosphor or packaging materials, the color of the LED will drift during the lifetime, the drift should be within the specified range (such as Δu'v' ≤ 0.007), beyond the range is considered LED failure;
Changes in electrical properties, electrical performance changes can be monitored more intuitively;
The number of switches, the switch may have a certain impact on the drive and other circuits;
Thermal resistance changes and other thermal characteristic parameters, thermal characteristics are closely related to life, and measurement and analysis of thermal characteristics can help identify weak links in LED reliability;
LED transient degradation (failure), that is, the LED light output suddenly drops to 0, its main degradation includes: anti-electromagnetic interference capability: electrostatic discharge, lightning surge, fast group pulse, cycle drop; high and low temperature impact tolerance characteristics; Salt spray, moisture resistance, vibration, etc.
3. Relevant standard requirements
In view of the main slow-degradation of LEDs, relevant standards have been released in the world, so that the North American system and the International Commission on Illumination (IEC) system are the most typical, and the Chinese standards basically combine these two systems.
ENERGY STAR® Program Requirements Product Specification Eligibility Criteria;
IES LM-80-08 Approved Method for Measuring Lumen Maintenance of LED Light Sources;
IES TM-21-11 Projecting Long Term Lumen Maintenance of LED Packages;
IEC/PAS 62717 LED modules for general lighting – Performance requirements;
EC/PAS 62722-2-1 Luminaire Performance – Part 2-1: Particular requirements for LED luminaires;
China's GB/T 24824, GB/T24823, QB/T4057, etc.;
China's GB/T XXXX LED accelerated life test method (not yet released).
The hand-held electric fan is intelligently controlled and adjusted in three gears, and the wind power can be adjusted according to your own needs. The lithium battery of the rechargeable fan has strong versatility, recyclable charging, low use cost, simple and elegant appearance, firm structure, small size, light weight and convenience. More unique designs for student travel and outdoor sports bring more comfort to more consumers.
Handheld Fan,Portable Hand Fan,Mini Hand Fan,Mini Handheld Fan
Guangdong Aiyimi Electronic Technology Co., Ltd. , https://www.seventreasuresfan.com