From time to time I come across a solution in which uses an LED as in below picture:
This particular component is placed inside the module located in car interior. Button backlight application.
The base LED [PLCC-2 Package] is blue color LED. The top cover material changes the light to white, so I assume this cover material is actually a phosphorus layer. This is a common approach of achieving white color but usually the phosphorus layer is integrated inside the PLCC-2 package (The die is sunk in phosphorus line on below picture.)
What is the purpose of this additional cover? My guesses are:
- Specially mixed phosphorus layer is added to finished LED in order to achieve exact white color coordinates.
- Manufacturing process improvement: one line for blue and white LEDs with additional process for white.
Is there any LED expert that could confirm this?