What Causes LED Lumen Depreciation? A Troubleshooting Guide from Chip to Operating Environment
A customer once told us the indicator lights on their equipment had dimmed by half after two years, and asked whether the diodes were simply poor quality. In fact, LED lumen depreciation is a very common problem with complex causes — the chip, bonding wire, lens material, drive method, and operating environment all play a part. This article breaks down the common causes one by one to help you troubleshoot and prevent them.
First, What Exactly Is Lumen Depreciation?
Lumen depreciation is the gradual decline in an LED's light output over time. The industry generally defines useful life as the point at which brightness falls to 70% of its initial value — the well-known L70. A quality LED diode operated under rated conditions for 50,000 hours can keep depreciation within 30%; with poor component selection or misuse, however, noticeable dimming within a few thousand hours is not uncommon.
Three Internal Causes Inside the Diode
First is the chip — the light-emitting core. There is a clear gap in aging resistance between A-grade and B/C-grade chips, and low-priced diodes often cut corners here. Second is the bonding wire: pure gold wire conducts well and resists oxidation, while some manufacturers substitute alloy or even copper wire; over time the bond oxidizes, resistance climbs, and brightness slowly fades. Third is the encapsulation lens: ordinary epoxy yellows under high temperature and UV exposure, absorbing part of the light before it ever escapes — and white LEDs add phosphor degradation on top of that.
External Causes in the Field Are Even More Common
In real-world failure cases, external causes outnumber internal ones. The table below lists the most common external causes, their typical symptoms, and how to prevent them:
| Cause | Typical Symptom | Prevention |
|---|---|---|
| Excessive drive current | An entire batch dims evenly; lamp bodies run hot | Design with 20% derating below the rated 20mA |
| Poor heat dissipation | LEDs closest to heat sources dim first | Keep diodes away from power transformers; leave thermal clearance on the board |
| ESD damage | Individual LEDs glow faintly or flicker | Use anti-static wrist straps and grounded workbenches on the production line |
| High temperature and humidity | Lens yellowing, lead corrosion | Choose waterproof lens materials for outdoor devices; add moisture protection inside control cabinets |
| Voltage fluctuation | Brightness flickers before decaying | Add a voltage regulation stage; never drive LEDs from an unregulated supply |
An Easily Overlooked Detail: Reflow Temperature
When SMD LEDs go through reflow soldering, a profile that ignores the datasheet — a peak above 260°C or too long in the high-temperature zone — inflicts latent damage on the lens and bonding wire inside the diode. These parts pass outgoing inspection at the factory, but lumen depreciation accelerates after six months in service. So during SMT assembly, always confirm the reflow profile with your assembly house; the soldering conditions in the datasheet are not just a formality.
What to Check When Selecting Low-Depreciation LEDs
In short: chip grade, bonding wire material, and lens formulation. When purchasing, ask the manufacturer for lumen depreciation test data — reputable packaging houses operate temperature- and humidity-controlled aging chambers and can provide measured 1,000-hour and 3,000-hour depreciation curves. Whether it is a 3mm or 5mm through-hole indicator or a 0603, 0805, or 1206 SMD part, the principle is the same. Our 0805 SMD LED diodes and 0603 SMD LED diodes both use A-grade chips with pure gold wire bonding; for through-hole options, see the Through-Hole LED Series. For projects with strict lumen-maintenance requirements, we recommend ordering samples first and running your own aging comparison.
Two Things Routine Maintenance Can Do
First, measure the drive current regularly — as equipment ages, power-supply output drifts and indicator current can quietly creep above rating; catching it early can still save the LEDs. Second, keep the operating environment dry and ventilated, especially for outdoor cabinets and equipment in humid climates or rainy seasons; moisture-induced lens degradation accounts for a considerable share of depreciation complaints. Get these two right, and standard indicators can stay bright for five to eight years.
About Hongcheng Optoelectronics
Dongguan Hongcheng Optoelectronics Co., Ltd. has over 20 years of LED packaging experience. Our products use A-grade chips and 99.9% pure gold wire bonding, and are RoHS certified. Our low-lumen-depreciation LED diodes support customization, free sampling, and volume quotations. Tel/WeChat: 139 2571 4318, Email: sales@led-hc.com.
