Low Profile Side Emitting LED with Flip-Chip and Phosphor Window
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Solution Overview
Problem
Conventional side-emitting LEDs have a high profile, limiting the thinness of backlights in small devices like cell phones and PDAs, and existing phosphor solutions for achieving high color gamut and uniformity are structurally weak and difficult to control.
Innovation Solution
The development of low-profile side-emitting LEDs with a flip-chip design and phosphor layers applied in a binder on a transparent window wafer, allowing for efficient side emission and precise control of color temperature through binning and matching of phosphor/window dice with blue LEDs, eliminating the need for lenses and enhancing light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional side-emitting LEDs with lenses are used, then light emission is achieved, but the profile height increases limiting backlight thinness
Solution Approach 1:
The patent removes the lens component from the LED structure entirely, extracting only the essential light-emitting elements (semiconductor chip, phosphor layer, reflector) needed to achieve side emission without the additional height imposed by lens assemblies
Solution Approach 2:
The patent inverts the conventional LED orientation by mounting the semiconductor chip with electrodes facing downward on a submount, causing light to emit sideways rather than upward, thereby eliminating the need for lenses and reducing profile height
2Manufacturing precision
If phosphor layer is made very thin to achieve high color gamut, then color temperature control is improved, but structural strength and color uniformity deteriorate
Solution Approach 1:
The patent creates a composite structure by embedding phosphor particles within a transparent binder material, forming a phosphor layer that is both thin for high color gamut and structurally supported by the binder for strength and uniformity
Solution Approach 2:
The patent changes the physical state and distribution parameters of phosphor by dispersing phosphor particles uniformly throughout a binder material, allowing precise control of color temperature while maintaining structural integrity through the binder matrix
3Manufacturing precision
If phosphor layer is made very thin to achieve high color gamut, then color emission control is improved, but color uniformity across surface deteriorates
Solution Approach 1:
The patent creates a composite structure by embedding phosphor particles within a transparent binder material, forming a phosphor layer that is both thin for high color gamut and structurally supported by the binder for strength and uniformity
Solution Approach 2:
The patent achieves homogeneous color distribution by uniformly dispersing phosphor particles throughout the binder material, ensuring consistent color emission across the entire phosphor layer surface while maintaining thin profile
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables the creation of thin, efficient backlights with improved light uniformity and high color gamut, reducing the thickness of the LED structure and enhancing light coupling into waveguides, while maintaining control over color emission and uniformity.
Implementation Method 1
phosphor layers for wavelength converting the light emitted from the active layer
Implementation Method 2
A reflector is provided over these other layers so that light impinging on the reflector is reflected back toward the active layer
Data Source
AI summary
Low profile, side-emitting LEDs are described that generate white light, where all light is emitted within a relatively narrow angle generally parallel to the surface of the light-generating active layer. The LEDs enable the creation of very thin backlights for backlighting an LCD. In one embodiment, the LED emits blue light and is a flip chip with the n and p electrodes on the same side of the LED. Separately from the LED, a transparent wafer has deposited on it a red and green phosphor layer. The phosphor color temperature emission is tested, and the color temperatures vs. positions along the wafer are mapped. A reflector is formed over the transparent wafer. The transparent wafer is singulated, and the phosphor/window dice are matched with the blue LEDs to achieve a target white light color temperature. The phosphor/window is then affixed to the LED.