"Six aspects" explain why LED power supply is afraid of sulfur

The LED light source is afraid of sulfur because the sulfur-containing gas undergoes a vulcanization reaction with the silver plating layer of the light source through the porous structure of the silica gel or the support gap. After the vulcanization reaction of the LED light source, the functional area of ​​the product will be blackened, the luminous flux will gradually decrease, and the color temperature will drift significantly. The vulcanized silver after vulcanization will increase in conductivity with increasing temperature, and it is prone to leakage during use; The condition is that the silver layer is completely corroded and the copper layer is exposed. Since the gold wire two solder joints are attached to the surface of the silver layer, when the silver layer of the bracket functional region is completely vulcanized and eroded, the golden ball appears to fall off, and a dead light appears.

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

LED lamps may contain sulfur/chlorine/bromine-containing materials:

1. Power supply: There are twenty or thirty kinds of raw materials in the built-in power supply of LED. Among them, PCB board, power cord with sulfur rubber, rubber-based insulating packaging plastic, plastic containing halogen flame retardant, electronic components, may contain sulfur. , chlorine and bromine elements. When the power supply is hot, these materials will volatilize sulfur/chlorine/bromine gas. When sulfur/chlorine/bromine gas is combined with nitrogenous water vapor, it will generate corrosive harmful gases and cause corrosion to the LED.

2. PCB board: The circuit board produced in the market has a certain content of sulfur residue. Although the PCB circuit board manufacturer will clean the board in the process process and eliminate the residue of sulfur-containing chemical solvent, the common production process is difficult to complete. Cleaned.

3. Sulphur-containing rubber power cord and rubber-based insulating packaging plastic: vulcanized rubber can maintain elasticity for a long time in the temperature range of -65~250 °C, and has excellent electrical properties and chemical stability, waterproof, ozone resistant and weather resistant. Aging, combined with simple usage and strong process applicability, is widely used in the electronics industry as a coating, potting and packaging material for electronic components.

4. Halogen-containing flame retardant materials: printed circuit board, outer casing, plastic, aluminum substrate insulation: PBB, PBDE, TBBP-A, PCB, hexabromododecane, tribromophenol, short-chain chlorinated paraffin and other halogen compounds Often used as a flame retardant, applied to printed circuit boards, casings, plastics and other materials. When these materials are heated to a certain temperature, the halogen-containing gas will be volatilized. When the halogen-containing gas is combined with the nitrogen-containing water vapor, corrosive harmful gases are generated, which cause corrosion to the LED. According to many scientific studies, halogen-based flame retardants have become pollutants that spread throughout the daily environment, releasing harmful substances during combustion and heating, threatening the health of the human body, the environment and the next generation. The use of halogen-based flame retardants is contrary to the environmental performance of LEDs. Therefore, Jinjian Testing recommends that LED material suppliers use halogen-free flame retardant materials as much as possible.

5. Solder paste flux: The activator component in the flux usually contains a small amount of halogen or organic acid component, which can quickly eliminate the oxide film on the surface of the soldered metal, reduce the surface tension of the solder, and spread the solder rapidly on the soldered metal. surface. The halogen is usually bromine/chlorine, which turns silver into black silver bromide/silver chloride.

6. Ink: Green oil on the PCB, white oil on the aluminum substrate, characters, lamps, and paint on the radiator may all contain sulfur. This is because there are sulfides in the crude oil in the paint, and its composition is very complicated, including elemental sulfur, hydrogen sulfide, mercaptans, thioethers, disulfides, and the like. Among them, active sulfides such as hydrogen sulfide, mercaptans and elemental sulfur can directly react with silver. Paint crude oil contains oilfield water and will contain salts such as sodium chloride, magnesium chloride and calcium chloride. In crude oil processing, magnesium chloride and calcium chloride are easily hydrolyzed to form hydrogen chloride which is highly corrosive. Therefore, Jinjian Testing recommends that LED material suppliers use sulfur-free or low-sulfur crude oil as paint.