LED Chip Phosphor Layer Gap Bridging for Uniformity
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Solution Overview
Problem
Conventional semiconductor light emitting apparatuses with color-converted LED chips experience variations in chromaticity and luminance due to uneven phosphor distribution, leading to color shifts and dark stripes between chips, which are difficult to eliminate without compromising luminous flux or increasing device size.
Innovation Solution
A wavelength conversion layer is applied to bridge the upper surfaces of LED chips, with thinner layers in gaps between them, using a phosphor material that is strategically positioned to reduce light absorption and enhance light emission uniformity, potentially incorporating reflective or scattering members to maintain luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a phosphor layer is directly formed on individual LED chips, then the chips can be coated with phosphor, but variations in chromaticity and luminance occur within the emission plane, particularly dark stripes between chips
Solution Approach 1:
The patent merges the phosphor coating process with a planarization layer formation, combining two functions into a single integrated structure. The planarization layer is formed to cover the gaps between chips and fill the uneven surfaces, creating a unified planar emission surface that eliminates dark stripes while maintaining uniform chromaticity across the entire emission plane.
Solution Approach 2:
The patent applies different properties to different regions: the phosphor layer is applied only on the upper surfaces of the chips where light is emitted, while the planarization layer extends into the gaps between chips to provide structural uniformity. This local differentiation allows the phosphor to convert light where needed while the planarization layer fills gaps to prevent dark stripe formation.
2Ease of manufacture
If the entirety of chips are coated with a phosphor layer including areas between chips, then phosphor is deposited uniformly, but the phosphor in between chips receives less excitation light, causing color shift towards yellow
Solution Approach 1:
The patent applies phosphor selectively only on the upper surfaces of the chips where excitation light is available, rather than depositing it uniformly across all surfaces including gaps. This localized application ensures that phosphor is positioned where it can effectively receive excitation light and convert it to the desired wavelength, preventing yellow color shifts in the emission plane.
3Manufacturing precision
If only the upper surface of individual chips are coated with phosphor, then uniform color mixture is obtained above chips, but non-light emitting portions between chips appear as dark stripes
Solution Approach 1:
The patent combines the phosphor coating function with a planarization layer that extends into the gaps between chips. While phosphor is applied only on chip upper surfaces for color conversion, the planarization layer fills the gaps to create a continuous planar emission surface, eliminating dark stripes by providing structural uniformity without interfering with the localized phosphor function.
4Manufacturing precision
If a phosphor layer is formed away from an array of LED chips, then chromaticity variations are reduced, but the light source size increases
Solution Approach 1:
The patent merges the phosphor layer with the chip structure itself by forming the planarization layer directly on and around the chips. This integration eliminates the need for a separate distant phosphor layer, maintaining a compact light source size while achieving uniform chromaticity through the combined structure that fills gaps and creates a planar emission surface.
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 configuration significantly reduces variations in chromaticity and luminance within the emission plane, preventing color shifts and dark stripes, while allowing for a compact light source design.
Implementation Method 1
a color mixture of primary light emitted by the semiconductor devices and secondary light which includes light that has been color-converted by a color-converting phosphor material
Data Source
AI summary
A light emitting apparatus with a combination of a plurality of LED chips and a phosphor layer is provided and can be configured to significantly reduce variations in chromaticity and luminance. The plurality of semiconductor light emitting devices (LED chips) are disposed with a gap therebetween, and the phosphor layer is formed on the upper surface thereof to bridge over the gaps between the LED chips. The phosphor layer may be uniform in thickness, but can be less in thickness over the gaps between the LED chips than on the upper surface of the LED chips. The phosphor layer can be continuously formed on the upper surface of the array of the chips with no phosphor layer present in between the chips. This configuration allows for reducing variations in luminance and chromaticity which may result from the gaps or the phosphor layer present in between the gaps.