LED Package Phosphor Compensation for Color Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional white LEDs experience variations in color hue due to variations in phosphor or conversion material coverage and material composition, leading to inconsistent emission wavelengths, which increases manufacturing costs and reduces customer satisfaction through the need for binning to ensure acceptable color ranges.
Innovation Solution
The use of two or more phosphors with tailored excitation and emission characteristics to compensate for LED emission wavelength variations, maintaining a consistent white emission color point by adjusting the excitation efficiency of each phosphor to match the target color point, thereby reducing the need for extensive binning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single phosphor or converter material is used with blue LEDs, then the device complexity is reduced and manufacturing is simplified, but the color point varies significantly due to LED wavelength variations and material composition variations
Solution Approach 1:
The patent applies composite materials by combining multiple phosphor materials (e.g., yellow phosphor and red phosphor) or using a phosphor converter material with specific composition ranges to create a multi-component phosphor system. This composite approach compensates for LED wavelength variations and maintains consistent color point output, resolving the contradiction between simplified material composition and stable emission characteristics.
2Stability of the object's composition
If LEDs are tested and sorted by color into bins to ensure acceptable color ranges, then the color consistency is improved, but the manufacturing cost increases and productivity decreases
Solution Approach 1:
The patent applies preliminary action by pre-engineering the phosphor material composition and converter material properties during manufacturing to inherently produce LEDs with consistent color points. This preliminary optimization of material characteristics eliminates the need for subsequent binning and sorting operations, thereby maintaining color consistency while improving productivity and reducing manufacturing costs.
3Use of energy by moving object
If the phosphor or converter material is optimized for a specific LED wavelength, then the emission efficiency is improved, but the color point varies when LED wavelength changes
Solution Approach 1:
The patent applies local quality by using multiple phosphor materials with different emission characteristics or a phosphor converter material with specific composition ranges. Each phosphor component contributes differently to the overall emission, with certain phosphors being more effective at compensating for wavelength variations in specific ranges. This localized optimization of phosphor properties across different wavelength regions maintains both emission efficiency and color point stability.
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 approach results in tighter emission distribution and more consistent LED packages, reducing manufacturing costs and improving customer acceptance by maintaining a consistent color point within a narrow standard deviation, such as within 4-step MacAdam ellipses on the CIE color coordinate system.
Implementation Method 1
The surrounding phosphor material 'downconverts' the wavelength of some of the LED's blue light, changing its color to yellow
Implementation Method 2
When a bias is applied across the doped layers, holes and electrons are injected into the active layer where they recombine to generate light
Data Source
Figure 1~2b
Figure 3a~2c
Figure 3b~3c
AI summary
A method for fabricating emitter packages (10) comprises fabricating a plurality of LEDs (14). Each of the LEDs (14) emits at a wavelength within a range of wavelengths. The LEDs (14) are each arranged in a respective package (10) with a plurality of conversion materials (24, 26) so that at least some light from each of the LEDs (14) is absorbed and re-emitted by its corresponding conversion material (24, 26). The plurality of conversion materials (24, 26) have excitation and emission characteristics that compensate for different LED emission wavelengths within the range such that each of the emitter packages (10) emits light within a standard deviation of a target color.