Pan Pacific Symposium Conference Proceedings


SILICONE-PHOSPHOR ENCAPSULATION FOR HIGH POWER WHITE LEDs

Authors: Horatio Quinones, Brian Sawatzky, and Alec Babiarz
Company: ASYMTEK
Date Published: 1/24/2008   Conference: Pan Pacific Symposium


Abstract: High-brightness Light Emitter Diodes (HB-LED) market has grown at an average rate of about 43% since the introduction of blue light wavelength die. HB-LEDs provide for a range of applications such as architectural lighting, signaling, entertainment lighting, automotive lights and LCD backlighting. The flexibility in color-changing properties, long life time, robustness, energy efficiency (lumens/watt) makes this technology very attractive. There are issues and challenges including the need to improve electronic drive circuit technology, total lumen output, “white light problem”, color quality and reproducibility and cost efficiency. HB-LEDs are not a simple die, they need to be packaged in a complex structure as to maximize the effective intensity and prevent optical aberrations. HBLEDs come in many packages, from single chip to sophisticated multi-directional aspheric lens designs. They include lenses, colored materials, and diffusers (one or two part silicone materials filled with phosphors) all of which can alter the spatial and spectral distribution relative to the basic light emitter die. Packages may include chips of different size, different types and different locations. Packages and chip locations may have different mechanical tolerances. Process for dispensing the fluids that constitute a large part of both, manufacturing and packaging of HBLEDs need to be precise reliable and cost effective. Jetting technology offers a five fold faster process, and higher precision than traditional needle dispensing. The paper addresses some of the challenges in the LED packaging in particular jetting processes that lead to tighter distribution of the HB-LED color spectra (CIE, XYZ map) which in turn reduces the binning of LEDs and reduces the packaging cost of ownership.

Key word: LED, jetting, dispensing, YAG, CIE, volumetric accuracy.





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