During the use of LED lighting fixtures, we often encounter situations where the LED chips turn black, leading to fixture failure. There are two main culprits behind this: sulfidation and bromination.
One of the key components that enables LED chips to emit light is the internal silver-plated substrate. However, this substrate is highly sensitive and can degrade upon coming into contact with certain elements, triggering a chemical reaction.
Sulfidation: When sulfur (S) penetrates the interior of the LED chip, it reacts with the silver-plated layer to form black silver sulfide (Ag₂S). This is the most common cause of LED blackening and brightness decay.
Bromination: In addition to sulfur, bromine (Br) also corrodes the silver-plated layer, forming light-black silver bromide (AgBr). The sources of bromine are often hidden.
You might be surprised to learn that these “killers” do not originate from external sources but are often lurking inside the lighting fixture or introduced during the manufacturing process.
The primary sources of sulfidation and bromination include the following:
1. Light Board/Circuit Board: If the white ink (white oil) on the PCB contains sulfur, it can volatilize in a high-temperature, sealed environment, directly causing sulfidation of the LED chips. Similarly, the insulation layer of aluminum substrates may contain bromine or chlorine, which can trigger bromination under specific conditions.
2. Metal heat sinks: During the acid washing process in heat sink production, if cleaning is incomplete, residual acidic substances can dissolve the silver plating on the LED mount, triggering chain reactions such as sulfidation and bromination.
3. Housing Paint/Adhesive: Some paint raw materials contain sulfides, while the encapsulation resin of LED chips expands its molecular gaps at high temperatures, similarly becoming a pathway for elements like sulfur and bromine to penetrate the interior.
4. Production Auxiliary Materials: The active ingredients in flux used during soldering may contain halogens (bromine/chlorine), which corrode the silver layer.
Sulfidation and bromination cause devastating damage to LED lights, gradually rendering them inoperable.
Luminous efficacy decline: Silver sulfide (Ag₂S) is a black substance that coats the reflector layer, leading to a gradual decrease in luminous flux.
Color temperature drift: Since light of different wavelengths is absorbed to varying degrees, this causes significant changes in color temperature.
Leakage/Lamp Failure: At high temperatures, silver sulfide becomes conductive, causing electrical leakage. In severe cases, the silver layer is completely corroded, and the gold wires detach, resulting in the lamp becoming completely inoperable.
Prevention at the Source: Choosing “High Sulfur-Resistant” Products Is Key
Since the problem lies in the materials, the most fundamental solution is to select high-quality products capable of withstanding these “harmful effects.”
PPL Technology: Some advanced manufacturers employ PPL technology to deposit a dense inorganic protective layer on the surface of the silver plating. This protective layer acts like an “invincible shield” for the silver, completely blocking the corrosion caused by sulfur, oxygen, bromine, and other substances, thereby solving the problem at its root.
International Standards: There is also an authoritative international testing standard for LED sulfurization resistance: IEC 60747-5-13:2021. When purchasing, asking whether the product has passed this test is a crucial basis for evaluating its sulfurization resistance.
Purchasing Guide: Ask the Right Questions, Request the Right Reports
Ask: Has this LED chip undergone sulfurization and bromination resistance treatment? What technology is used? (e.g., PPL technology)
Request: Can you provide a report confirming the product has passed the IEC 60747-5-13 anti-sulfidation corrosion test?
Inspect: Carefully examine the LED chip’s silver plating layer to check for uniform color and any signs of blackening or discoloration.
Failure Analysis and Resolution Process
If blackening has already been detected in the lighting fixture, follow these steps:
--Conduct a visual inspection to preliminarily determine if the silver plating has blackened.
--Send suspected contaminated materials (such as circuit boards, heat sinks, etc.) for testing to identify the source of contamination through professional methods.
The blackening of LED chips is essentially a chemical failure process caused by the silver plating being “poisoned” by sulfur or bromine elements, which can significantly shorten the lifespan of the luminaire. The source of contamination may be hidden in any part of the luminaire—from the PCB to the heat sink, and even in production auxiliary materials—it is ubiquitous. Therefore, in addition to isolating contamination sources during production and use, the most effective approach during procurement is to prioritize products that feature advanced anti-sulfidation and anti-bromination technologies (such as PPL technology) and can provide corresponding authoritative test reports.
✅ Priority Selection: LED chips featuring advanced anti-sulfidation/anti-bromination technologies such as PPL
-- Required Reports: Passed IEC 60747-5-13 testing
-- Visual Inspection: Silver plating should be uniform in color, with no blackening or discoloration
-- Professional Analysis: Commission a testing agency to analyze blackened samples to identify the source of contamination