Phosphor Sheet Lamination for LED Color Temperature Uniformity
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Solution Overview
Problem
Existing methods for producing white light from LEDs result in inconsistent color temperatures due to variations in LED color emission and phosphor deposition, leading to complexity and variability in phosphor application.
Innovation Solution
A process involving the formation of LED bins based on color emission, followed by the use of thin, flexible encapsulant sheets with varying phosphor concentrations and thicknesses, specifically designed for each bin, to achieve uniform color temperature through empirical testing and lamination of phosphor sheets over LEDs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the same phosphor coating is applied to all LEDs, then the fabrication process is simple, but the output color temperature varies greatly due to LED variations
Solution Approach 1:
The patent applies different phosphor coatings to different bins of LEDs based on their specific color emission characteristics. LEDs are first sorted into bins according to their wavelength, then each bin receives a phosphor coating optimized for that specific bin's characteristics, achieving uniform white light output across all LEDs while maintaining manufacturing efficiency
Solution Approach 2:
The patent performs preliminary binning of LEDs by wavelength before phosphor deposition. This preliminary sorting action allows subsequent phosphor coatings to be optimized for each bin, preventing color temperature variations before they occur rather than correcting them afterward
2Illumination intensity
If phosphor particles are mixed in encapsulation material and coated over LEDs, then white light can be produced, but the phosphor deposition process becomes complex and phosphor amount varies from LED to LED
Solution Approach 1:
The patent segments the phosphor deposition process by applying different phosphor coatings to different LED bins. Rather than using a single complex deposition process for all LEDs, the process is divided into separate coating steps for each bin, simplifying the overall approach while achieving consistent results
Solution Approach 2:
The patent changes phosphor coating parameters (such as phosphor type, concentration, or layer thickness) based on the specific wavelength characteristics of each LED bin. This parameter adjustment for each bin eliminates the need for complex variable deposition processes while maintaining simple, repeatable fabrication steps
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 ensures a uniform color temperature across LEDs with varying color emissions, simplifying the phosphor deposition process and maintaining consistent output color, despite variations in LED characteristics.
Implementation Method 1
One way of producing white light from an LED structure is to deposit a yellow phosphor over a blue LED
Implementation Method 2
the phosphor sheet is permanently laminated onto the LEDs and submount such as by heat and pressure
Data Source
AI summary
A process is described for wavelength conversion of LED light using phosphors. LED dies are tested for correlated color temperature (CCT), and binned according to their color emission. The LEDs in a single bin are mounted on a single submount to form an array of LEDs. Various thin sheets of a flexible encapsulant (e.g., silicone) infused with one or more phosphors are preformed, where each sheet has different color conversion properties. An appropriate sheet is placed over an array of LED mounted on a submount, and the LEDs are energized. The resulting light is measured for CCT. If the CCT is acceptable, the phosphor sheet is permanently laminated onto the LEDs and submount. The lamination encapsulates each LED to protect the LEDs from contaminants and damage. The LEDs in the array of LEDs on the submount are separated. By selecting a different phosphor sheet for each bin of LEDs, the resulting CCT is very uniform across all bins.