Multiple factors can affect LED performance, reliability, and lifespan. Design engineers and those working with LED components must take these factors into account. The causes of LED performance degradation can be categorized into three types of stressors: electrical, thermal, and contamination stress.
The three types of stressors that cause LED performance degradation or failure.
To fully benefit from Luminus LEDs’ high-performance functionality, contamination prevention, power supply design, and thermal management should all be carefully considered in luminaire design with reference to best practices. Otherwise, LED performance will be hindered, and failure or other permanent damage may occur.
Contamination Damage
LED devices are sensitive to contamination damage. Contaminated devices can appear dim, develop an open circuit, or become shunted. It is important to understand the circumstances that cause damage to an LED, as it is often catastrophic.
Common contamination-driven mechanisms of LED dimming are:
- Exposure to Volatile Organic Compound (VOC) contaminants
- Exposure to Sulfur-containing contaminants, causing sulfur metallization corrosion
- Poor ventilation practices in fixture design
- Carbonization of contaminants on the silicone dome encapsulation
- Silicone swelling
- High system operating temperatures
- Excessive voids in the soldering joints, which can amplify the effect of contaminants, cause carbonization, and lead to higher-than-expected LED temperatures.
These contamination sources and mechanisms can be avoided or mitigated. To learn more, read the Application Note Guidelines to Prevent LED Damage Due to Contamination.
Electrical Stress Damage
Electrical stress factors include electrical overstress (EOS), electrostatic discharge (ESD), and
reverse polarization. Root causes of electrical stress can be transient external conditions, system design flaws, or component-level issues due to defects or poor handling. JEDEC conducted a global survey to summarize potential root causes of electrical stress damage on LEDs, refer to the figure below.
To learn more about prevention, troubleshooting, and remedying electrical stress damage in Luminus LED components, refer to the Application Note Electrical Stress Damage to LEDs and How to Prevent It.
Summarizing the Root Causes of Electrical Stress Damage, adapted from JEP 1741
Thermal Damage
A common customer complaint heard by LED manufacturers is that the measured light level in a luminaire is lower than the data sheet specifications indicate. Upon further investigation, it often becomes clear that the low optical efficiency is a symptom of poor thermal management in the system design. This is most evident when the p-n junction temperature exceeds the specified operating limits.
A more subtle symptom of thermal damage is decreased LED lifetimes, or an increased rate of wear-out and failure. This LED failure mechanism may be obvious if currents far exceeding the specified limits are used, which quickly overstresses the device. However, temperature overstress effects may be subtle if the p-n junction temperature is not significantly greater than the data sheet temperature limit.
The thermal factors that cause LED performance degradation are much more complex than those that cause electrical overstress or contamination. The thermal design of LED systems has a profound impact on performance and lifetime of an LED product and thermal factors can be extremely complicated to analyze, requiring a system-level approach that accounts for multiple variables.
Learn more about thermal damage causes and prevention in the Application Note: Thermal Management of Big Chip LEDs.
- JEP174 - Understanding Electrical Overstress. 2016.
--------------------------------------------------------------------------------------------------------------------
Luminus Website https://www.luminus.com/
Luminus Product Information (datasheets): https://www.luminus.com/products
Luminus Design Support (ray files, calculators, ecosystem items: [power supplies, lenses, heatsinks]): https://www.luminus.com/resources
Luminus Product Information sorted by Applications: https://www.luminus.com/applications
Where to buy Samples of Luminus LEDs: https://www.luminus.com/contact/wheretobuy.
--------------------------------------------------------------------------------------------------------------------
Comments
0 comments
Please sign in to leave a comment.