LED Package Phosphor Coating via Liquid Encapsulant Settling
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Solution Overview
Problem
Conventional LED packages face issues with non-uniform white light emission due to variations in phosphor coating and thermal expansion mismatches, leading to color inconsistencies and reliability problems.
Innovation Solution
A method for fabricating LED packages involves depositing a liquid encapsulant over the LED chip, allowing an optical element to settle on it, and curing the encapsulant, which allows for controlled thickness and shape, and includes features to manage thermal expansion mismatches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If phosphor particles are suspended in solvent and allowed to flow to LED surface using electrostatic charge, then phosphor coating uniformity is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent extracts the phosphor particles from the complex electrostatic deposition process and applies them directly to the LED chip surface using a simpler method. The phosphor is applied in paste form directly onto the chip, eliminating the need for electrostatic charge control and solvent suspension, thus reducing manufacturing complexity while maintaining coating uniformity.
Solution Approach 2:
The patent uses a simple, disposable phosphor paste application method that does not require complex electrostatic equipment. The phosphor paste is applied directly and cured, eliminating the need for expensive and complex electrostatic deposition systems, making the process more suitable for mass production.
2Reliability
If phosphor containing matrix material extends above the cup rim, then encapsulation is improved, but color uniformity deteriorates due to predominance of converted light at high viewing angles
Solution Approach 1:
The patent applies phosphor directly onto the LED chip surface rather than using a bulk phosphor-containing matrix that extends above the cup rim. This localized application ensures that the phosphor is positioned exactly where needed for optimal color conversion, preventing the formation of non-uniform layers and eliminating the color variation problem at different viewing angles.
Solution Approach 2:
The phosphor is applied to the LED chip surface before the encapsulant is molded. This preliminary application ensures that the phosphor is in the correct position and orientation before the encapsulant is formed, preventing the formation of non-uniform phosphor layers that would cause color variation at different viewing angles.
3Reliability
If large volume of encapsulant is used to fill the package, then encapsulation is improved, but thermal stress increases due to coefficient of thermal expansion mismatch
Solution Approach 1:
The patent uses a thin layer of encapsulant rather than a large volume. The encapsulant is applied as a thin coating that provides sufficient protection and encapsulation while minimizing the volume of material that would expand and contract with temperature changes, thereby reducing thermal stress on the LED chip and wire bonds.
Solution Approach 2:
The patent extracts the encapsulant from being a large-volume bulk material and transforms it into a thin protective layer. This reduces the amount of encapsulant material present in the package, minimizing the thermal expansion mismatch and associated thermal stress while still providing adequate encapsulation and protection.
4Manufacturing precision
If electrophoretic deposition is used to coat phosphor directly on LED, then color uniformity is improved, but manufacturing speed decreases and process control becomes difficult
Solution Approach 1:
The patent uses a simple phosphor paste application method that can be quickly applied and cured without the need for complex electrostatic deposition equipment. This straightforward approach is much faster and easier to control in a mass production environment, significantly improving manufacturing speed while still achieving uniform phosphor coating.
Solution Approach 2:
The patent extracts the phosphor application process from the complex electrophoretic deposition system and simplifies it to a direct paste application method. This eliminates the need for solvent suspension, electrostatic charge control, and complex process parameters, making the process much faster and easier to control for mass production while maintaining coating uniformity.
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 LED packages with improved color uniformity and reduced thermal stress, enhancing the reliability and emission efficacy of white light emission.
Implementation Method 1
allowing an optical element to settle on it
Implementation Method 2
curing the encapsulant
Data Source
AI summary
Methods for fabricating LED packages comprising providing an LED chip and covering at least part of it with a liquid medium. An optical element is provided and placed on the liquid medium. The optical element is allowed to settle to a desired level and the liquid medium is cured. LED packages are also disclosed that are fabricated using the disclosed methods.