If you want LED lamp beads to play the best performance, not only need to start from the design, but also the chemical reactions that occur around the LED lamp bead products are also one of the factors that need to be considered. If the chemical reaction is not handled properly, it is likely to cause irreversible damage to the performance of the LED. This article will start from the point of view of chemical reactions and talk about chemical reactions that should be paid attention to in LEDs.
1. The workshop environment should be kept at a temperature below 30 degrees and a humidity within the range of 40%RH-60%RH.
A thermometer and hygrometer can be used to monitor environmental changes, and gloves or finger cots should be worn when contacting the LED for inspection. The packaging bag should be sealed in time after it is opened to prevent oxidation of the feet.
2. Avoid exposing the LED to the acidic (PH<7) workshop environment.
For other purchased LED assembly materials, the manufacturer can be required to provide the MSDS report (material safety data sheet) of the original material to confirm whether it contains sulfur, (such as MCPCB sheet, rubber gloves, rubber bands, sulfur soap, etc.) ), halogen-based substances (such as glass glue, low-end two-component resin glue) to prevent chemical or physical reactions with LED materials, such as LED contact with sulfur or halogen-containing substances or stored in an acidic environment, extremely It is easy to cause corrosion of the silver-plated layer of LED products, variation of the properties of LED silica gel and phosphor materials, resulting in the failure of the photoelectric performance of LED lamp beads.
3. The user side must pay special attention to the protection of sulfur during the production process, and select quality-guaranteed MCPCB plates and solder pastes and other auxiliary materials (not containing sulfur, halogen, etc. or the content is lower than the safety standard).
From the EDS analysis of MCPCB sheets in several cases in the past, it can be seen that many sheets produced on the market have different levels of sulfur. Although MCPCB manufacturers will clean the sheets during the manufacturing process to eliminate sulfur and sulfur content. The residues of acid chemical solvents, but it is difficult to completely eliminate them in the ordinary production process. For this, the residual sulfur content of the MCPCB board needs to be quality controlled. Generally, the maximum sulfur (S) content on the MCPCB copper foil does not exceed 0.5% as the upper limit standard.
4. When the LED is mounted on the chip (SMT), the following temporary measures can be used to prevent it:
A. Sulfur is more active at high temperatures. You can pass the MCPCB board through a high-temperature reflow oven (about 230 degrees) before surface mounting and then do surface cleaning (medical alcohol, etc.) (if conditions do not permit it) Next, you can directly clean the MCPCB surface before mounting) to reduce the sulfur content of the MCPCB pad and surface layer.
B. Regularly clean the reflow oven and the dehumidification oven to reduce the sulfur or halogen content;
Control the workshop environment of LED or LED-containing components during welding, processing and application, and control the content of sulfur or halogen.
5. During the welding and processing of LED lamp beads, please do not use auxiliary materials containing sulfur or halogen (such as rubber gloves, rubber finger cots, rubber bands, filled plastic glass glue, hot melt glue, etc.) to contact the LED.
The chemical problem is not like an LED lighting circuit if there is an error, which can usually be corrected by replacing the device, but it will cause more difficult to reverse damage to the circuit. So everyone needs to pay special attention to these issues when designing.
The above 5 points are some chemical issues that LED lamp bead designers need to pay attention to. The chemical problem is not like if there is an error in the LED lighting circuit, it can usually be corrected by replacing the device, but it will cause more difficult to reverse damage to the circuit. So everyone needs to pay special attention to these issues when designing. I hope you can gain something after reading this article
