LED reliability testing technology: full lifecycle verification from accelerated aging to failure analysis

Keywords: LED reliability testing, accelerated aging, failure analysis, thermal cycling, salt spray test

abstract

Reliability is the core competitiveness of LED products. This article analyzes the technical methods and engineering practices of accelerated aging, environmental testing, and failure analysis.

5.1 Limitations of Traditional Aging Testing

Constant current aging: Under an environment of 85 ℃/85% RH, continuously light up for 1000 hours at 70% rated current, but cannot simulate the current fluctuations in actual use (such as dimming applications).

Luminous flux maintenance rate: After 6000 hours of testing with LM-80, if the light attenuation is greater than 30%, it is considered invalid (although some manufacturers use the "test truncation" method to falsely label the lifespan).

5.2 Accelerated Aging Testing Method

Temperature cycling test: According to IEC 60068-2-14, cycle 1000 times between -40 ℃ and 125 ℃, each time for 30 minutes, and detect solder joint cracking (such as SMD LED pin fracture rate>5% to determine failure).

Current pulse test: Simulate the working mode of car LED daytime running lights (10% duty cycle, 10A pulse current), detect the melting of the bonding wire (failure standard is a 20% decrease in luminous flux).

5.3 Environmental adaptability test

Salt spray test: according to ASTM B117, detect the corrosion of metal parts by spray in 5% NaCl solution at 35 ℃ for 48 hours (if the corrosion area of aluminum substrate is greater than 3%, it will be judged as invalid).

UV aging: Using a QUV accelerated aging chamber (UVA-340 tube, irradiance 0.76W/m 2), test for 1000 hours and determine failure if the color coordinate shifts (Δ u'v '>0.006).

5.4 Failure Analysis and Improvement

Scanning Electron Microscope (SEM): Observe LED chip cracks (such as p-n junction melting caused by ESD breakdown) and solder joint voids (void ratio>25% affecting thermal conductivity).

Thermal resistance test: T3Ster transient thermal tester is used to measure the difference between junction temperature (Tj) and shell temperature (Tc) (Δ T=Tj Tc). When the thermal resistance is greater than 15K/W, the heat dissipation structure needs to be optimized.

5.5 Standardization and Certification System

ENERGY STAR certification: LED lamps are required to have a lifespan of ≥ 25000 hours (L70), a light efficiency of>100lm/W, and a light decay of<15% within 5 years.

LM-84 report: Testing the luminous flux maintenance rate of dimmable LEDs at different dimming levels (such as light attenuation<20% at 10% brightness).

conclusion

Reliability testing needs to shift from "single aging" to "full lifecycle verification". By accelerating aging, environmental testing, and failure analysis, the durability and user trust of LED products can be improved.