Color Converted LED With Segmented Phosphor Deposition
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Solution Overview
Problem
Existing methods for generating white light using LEDs, particularly with blue or UV LEDs and phosphors, face challenges in achieving consistent and predictable color temperature and uniformity, often resulting in visually unpleasing high temperature white light and large light sources with limited emission patterns.
Innovation Solution
The technique employs electrophoretic deposition to conformably coat LED dies with a first phosphor, followed by a binder-based deposition of a second phosphor to create a controlled white light emission, allowing for precise control over phosphor thickness and coverage, and the use of a silicone lens to encapsulate the LEDs, ensuring consistent and uniform color temperature in the range of 2000K-5000K.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If phosphors are deposited in a reflective cup surrounding the LED, then white light can be generated, but the light source becomes relatively large and the emission pattern is limited
Solution Approach 1:
The patent divides the phosphor application into two separate stages: first applying phosphor directly to the LED die surface, then applying additional phosphor to the encapsulant. This segmentation allows each phosphor layer to be optimized independently, achieving desired color temperature without requiring a large reflector cup structure.
2Illumination intensity
If phosphors are mixed in a bonding medium and deposited on the LED, then white light can be generated, but the phosphor thickness varies making it difficult to achieve desired color temperature and uniform color
Solution Approach 1:
The patent separates the phosphor application into distinct layers: a first phosphor layer applied to the LED die and a second phosphor layer applied to the encapsulant. This eliminates the mixing problem entirely, as each layer can be controlled independently for uniform thickness and consistent color properties.
Solution Approach 2:
The first phosphor is applied to the LED die before encapsulation, establishing a controlled base layer. This preliminary action ensures uniform thickness and predictable light conversion before the second phosphor is added to the encapsulant material.
3Illumination intensity
If two or more phosphors are deposited in conjunction, then white light can be generated, but it is difficult to create predictable and consistent light color due to different phosphor reactions during deposition
Solution Approach 1:
The patent applies phosphors in two separate deposition processes rather than mixing them. The first phosphor is deposited on the LED die, then the second phosphor is deposited in the encapsulant material. This segmentation eliminates interactions between different phosphors during deposition, ensuring predictable and consistent light color output.
Solution Approach 2:
The encapsulant material serves as an intermediary medium for applying the second phosphor. This allows the second phosphor to be applied uniformly without direct interaction with the first phosphor on the LED die, eliminating compatibility issues and ensuring consistent color rendering.
4Temperature
If a yellow-green phosphor is used with a blue LED, then high temperature white light is produced, but the light is not visually pleasing and has poor color rendering
Solution Approach 1:
The patent uses a composite phosphor system with two different phosphors: a first phosphor (yellow-green, e.g., YAG) applied to the LED die and a second phosphor (red, e.g., CaAlSiN3) applied to the encapsulant. This composite approach combines the high temperature output of the yellow-green phosphor with the warm red components from the second phosphor, achieving both desired color temperature and superior color rendering.
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 method enables the production of warm white light with high controllability over color temperature and uniform emission, suitable for applications like automobile headlamps, while minimizing the issues of phosphor reactivity and physical/chemical incompatibilities, resulting in a more aesthetically pleasing and efficient light source.
Implementation Method 1
The deposition technique is electrophoretic deposition (EPD), which plates the die with a phosphor by applying a potential to the die and charging the phosphor in a solution. The attractive force evenly coats the die with the phosphor.
Implementation Method 2
A first phosphor for producing red, yellow, or yellow-green light is deposited to conformably coat the LED die
Data Source
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AI summary
A technique for forming a white light LED is disclosed. In one embodiment, the LED emits blue light. A first phosphor for producing red, yellow, yellow-green, or green light is formed to conformably coat the LED die. One suitable deposition technique is electrophoretic deposition (EPD). Over the resulting LED structure is deposited another phosphor (to add the remaining color component) in a binder (e.g., silicone) for encapsulating the die. The blue LED light combines with the two phosphor colors to create white light. Since the two different deposition techniques are independent and easily controllable, the resulting white light temperature is highly controllable and the color emission is substantially uniform.