The LED light source is afraid of sulfur because the sulfur-containing gas will vulcanize with the silver plating layer of the light source through the silica gel or support gap of its porous structure. After the vulcanization reaction of LED light source, the product functional area will blacken, the luminous flux will gradually decrease, and the color temperature will drift obviously; After vulcanization, the conductivity of silver sulfide increases with the increase of temperature, and electric leakage is easy to occur in the process of use; The more serious situation is that the silver layer is completely corroded and the copper layer is exposed. As the gold wire 2 solder joint is attached to the surface of the silver layer, when the silver layer in the functional area of the support is completely vulcanized and corroded, the gold ball falls off, resulting in dead lamp.

There are more than 50 kinds of raw materials in LED lamps, which may also contain sulfur, chlorine and bromine. In a closed and high-temperature environment, these sulfur, chlorine and bromine elements may volatilize into gas and corrode the LED light source. Therefore, the lighting factory has the responsibility and obligation to provide sulfur free environment for LED light source.

What is the effect of vulcanization reaction of LED light source

Materials that may contain sulfur / chlorine / bromine in LED lamps:

1. Power supply: there are twenty or thirty kinds of raw materials in the built-in power supply of LED, including PCB board, power line of sulfur-containing rubber, rubber insulating packaging plastic, plastic containing halogen flame retardant and electronic components, which may contain sulfur, chlorine and bromine. When the power supply is heated, these materials will volatilize sulfur \ chlorine \ bromine gas. When sulfur \ chlorine \ bromine gas is combined with nitrogen-containing water vapor, it will generate corrosive harmful gas and cause corrosion to LED.

2. PCB board: PCB boards produced on the market have a certain amount of sulfur residue. Although PCB board manufacturers will clean the boards in the manufacturing process to eliminate the residue of sulfur-containing chemical solvent, it is difficult to completely clean them in the ordinary production process.

3. Power lines of sulfur-containing rubber and rubber insulation packaging plastics: vulcanized rubber can maintain elasticity for a long time in the temperature range of – 65 ~ 250 ℃, and has excellent electrical properties and chemical stability. It can be waterproof, ozone resistant and weather aging resistant. In addition, it is simple to use and has strong process applicability. Therefore, it is widely used in the electronic industry as coating, pouring and sealing of electronic components packaging.

4. Halogen containing flame retardant materials: printed circuit board, shell, plastic, aluminum substrate insulation: PBB, PBDE, TBBP-A, PCB, hexabromododecane, tribromophenol, short chain chlorinated paraffin and other halogen compounds are often used as flame retardants in printed circuit board, shell, plastic and other materials. When these materials are heated to a certain temperature, they will volatilize halogen-containing gas. When halogen-containing gas is combined with nitrogen-containing water vapor, it will generate corrosive harmful gas and cause corrosion to LED. In addition, according to many scientific studies, halogen flame retardants have become ubiquitous pollutants in the daily environment. They will release harmful substances in the process of combustion and heating, threatening human health, the environment and the next generation. The use of halogen flame retardant is contrary to the environmental protection performance of LED. Therefore, Jinjian recommends that led material suppliers try to use halogen-free flame retardant materials.

5. Solder paste flux: the activator component in the flux usually contains a few halogen or organic acid components, which can quickly eliminate the oxide film on the surface of the welded metal, reduce the surface tension of the solder and make the solder spread on the surface of the welded metal. Halogen usually uses bromine / chlorine, which can turn silver into black silver bromide / silver chloride.

6. Ink: green oil on PCB, white oil on aluminum substrate, characters, paint on lamps and radiators may contain sulfur. This is because there is sulfide in the original oil of the paint, and its composition is very complex, including elemental sulfur, hydrogen sulfide, mercaptan, sulfide, disulfide, etc. Active sulfides, such as hydrogen sulfide, mercaptan and elemental sulfur, can react directly with silver. Oil paint crude oil contains oilfield water, which will contain salts such as sodium chloride, magnesium chloride and calcium chloride. In crude oil processing, magnesium chloride and calcium chloride are easily hydrolyzed by heating to produce highly corrosive hydrogen chloride. Therefore, Jinjian test recommends that led material suppliers choose sulfur-free or low sulfur crude oil as paint.

Source: OFweek semiconductor lighting network

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