Phosphor Placement in White LED Assemblies

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Solution Overview

Problem

White LED assemblies face inefficiencies in heat management and interabsorption of light due to the placement of phosphor materials, which affects the color spectrum and overall performance.

Innovation Solution

The placement of a first volume of red-emitting phosphor material surrounding the blue LED die and a second volume of yellow/orange and green-emitting phosphor material above the die, with the red-emitting phosphor material being in close proximity to the heat-sinking substrate to manage heat effectively and reduce interabsorption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If phosphor materials are placed in conventional positions in white LED assemblies, then the structure is simple and easy to manufacture, but heat management becomes inefficient and interabsorption of light increases

Engineering Contradiction:

Improveheat management efficiencyVSAvoidphosphor placement structure

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The phosphor materials are segmented into distinct spatial zones: red-emitting phosphor is placed in a first volume surrounding the blue LED die laterally, while yellow/orange and green-emitting phosphors are placed in a second volume above the die. This segmentation separates heat-generating red phosphor from the heat-sensitive blue LED, improving thermal management while reducing light interabsorption between different phosphor types.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention transitions from conventional planar phosphor placement to a three-dimensional volumetric arrangement. The red-emitting phosphor occupies a lateral volume surrounding the die, while yellow/orange and green phosphors occupy an upper volume. This dimensional change enables superior heat dissipation pathways and minimizes optical interference between phosphor layers.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Use of energy by moving object

If red-emitting phosphor material is placed close to the blue LED die, then light conversion is efficient, but heat dissipation becomes problematic

Engineering Contradiction:

Improvelight conversion efficiencyVSAvoidheat dissipation

Core Design Contradiction:

Use of energy by moving objectVSTemperature

Solution Approach 1:

The red-emitting phosphor is placed in a specific local region (first volume) that surrounds the blue LED die laterally but maintains appropriate spacing. This localized placement optimizes light conversion efficiency where needed while avoiding excessive heat concentration in any single spot, allowing thermal energy to dissipate through the lateral arrangement rather than concentrating directly above the heat-generating die.

Inventive Principle:

Principle #3Local quality

3Stability of the object's composition

If multiple phosphor materials are placed in the same region, then the device structure is compact, but interabsorption of light increases affecting color spectrum

Engineering Contradiction:

Improvecolor spectrum stabilityVSAvoidphosphor material volume arrangement

Core Design Contradiction:

Stability of the object's compositionVSVolume of stationary object

Solution Approach 1:

Different phosphor materials are segmented into separate spatial volumes: red-emitting phosphor in the first lateral volume, and yellow/orange and green-emitting phosphors in the second upper volume. This spatial segmentation prevents interabsorption of light between different phosphor types, ensuring each phosphor emits its characteristic wavelength without interference, thereby stabilizing the overall color spectrum while maintaining a compact integrated structure.

Inventive Principle:

Principle #1Segmentation

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 enhances heat dissipation from the less-efficient red phosphor material and minimizes interabsorption, resulting in improved light output and color temperature stability.

Implementation Method 1

A particular red-emitting phosphor particle may, for example, absorb blue light emitted form the LED die. The blue light has a wavelength of 455 nm. The red-emitting phosphor particle then re-emits some of the absorbed energy as red light.

Methodology Applied

Scientific EffectPhotoluminescence: Photoluminescence

Implementation Method 2

the red-emitting phosphor material being in close proximity to the heat-sinking substrate to manage heat effectively

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS8653554B2Phosphor placement in white light emitting diode assemblies

Publication Date: 2014.02.18 BRIDGELUX INC

AI summary

A white LED assembly includes a blue LED die attached to a substrate. A first volume of a first luminescent material surrounds the blue LED die in a lateral dimension such that none of the first luminescent material is disposed directly over the blue LED die. The first luminescent material includes a relatively inefficient phosphor having a peak emission wavelength longer than 620 nm and includes substantially no phosphor having a peak emission wavelength shorter than 620 nm. A second volume of a second luminescent material is disposed over the first volume and the blue LED die. The second luminescent material includes a relatively efficient phosphor having a peak emission wavelength shorter than 620 nm and includes substantially no phosphor having a peak emission wavelength longer than 620 nm. Placement of the first and second luminescent materials in this way promotes removal of heat from the inefficient phosphor and reduces the likelihood of interabsorption.