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Proceedings Paper

A new wafer level coating technique to reduce the color distribution of LEDs
Author(s): B. Braune; K. Petersen; J. Strauss; P. Kromotis; M. Kaempf
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Paper Abstract

Light emitting Diodes (LEDs) which use phosphor conversion might be a neat alternative to the more costly 3 chip RGB (red, green, blue) LEDs. Almost any color of phosphor conversion LEDs (pc-LEDs) can be adjusted by combining a light-emitting semiconductor chip and one or more phosphors. Depending on the ratio of unconverted and converted light, it is possible to verify both unsaturated and saturated colors. A very common type of phosphor conversion LED is composed of a reflector cavity, which contains a blue light emitting chip and is filled by a phosphor containing resin. At a fixed concentration, parameters like the thickness of the phosphor filled resin layer (conversion layer) above the chip and the wavelength influence the final color of the pc-LED. It is necessary to reduce the variation of the influencing parameters to be able to control the color and prevent yield losses in the production. A new phosphor coating technique developed at OSRAM OS makes it possible to precisely control the thickness of the conversion layer above the chip. A layer of a hard resin is applied on top of a wafer and afterwards its thickness is milled accurately to the desired value. With this new technique the color distribution can be reduced significantly compared to the common techniques.

Paper Details

Date Published: 13 February 2007
PDF: 11 pages
Proc. SPIE 6486, Light-Emitting Diodes: Research, Manufacturing, and Applications XI, 64860X (13 February 2007); doi: 10.1117/12.697972
Show Author Affiliations
B. Braune, OSRAM Opto Semiconductors (Germany)
K. Petersen, OSRAM Opto Semiconductors (Germany)
J. Strauss, OSRAM Opto Semiconductors (Germany)
P. Kromotis, OSRAM Opto Semiconductors (Germany)
M. Kaempf, OSRAM Opto Semiconductors (Germany)


Published in SPIE Proceedings Vol. 6486:
Light-Emitting Diodes: Research, Manufacturing, and Applications XI
Klaus P. Streubel; Heonsu Jeon, Editor(s)

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