LED Package Meniscus Lens for Bubble-Free Encapsulation
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Solution Overview
Problem
Existing LED packages face issues with light loss due to total internal reflection and complexity in optics, as well as thermal expansion mismatch leading to delamination and reduced light extraction, caused by the use of lenses with different coefficients of thermal expansion compared to package components.
Innovation Solution
The method involves using a meniscus ring with a meniscus holding feature to maintain a bubble-free, hemispheric shape of the encapsulant, allowing a concave optical element with a larger radius of curvature to be placed over the LED chip, minimizing air entrapment and ensuring proper alignment, which reduces stress and enhances light extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a solid hemispherical lens is used with a flat or planar surface, then the lens can be easily manufactured and mounted, but air bubbles are trapped between the lens and encapsulant during fabrication, reducing light extraction efficiency
Solution Approach 1:
The patent applies curvature to the bottom surface of the lens by forming a meniscus shape in the encapsulant material. The encapsulant is shaped to have a curved bottom surface that matches the curvature of the lens, eliminating air gaps and ensuring complete optical contact between the lens and encapsulant, thereby maximizing light extraction efficiency
2Adaptability or versatility
If a lens with different coefficient of thermal expansion (CTE) compared to package components is used, then optical functionality is achieved, but thermal expansion mismatch causes delamination and cracking of LED chip or package elements
Solution Approach 1:
The patent changes the physical state of the encapsulant material from solid to liquid during assembly, allowing the lens to be positioned and the encapsulant to conform to the lens shape before curing. This parameter change enables the encapsulant to adapt to thermal expansion differences, reducing stress and preventing delamination during thermal cycling
3Strength
If the LED chip is placed below the origin of the hemispherical lens to allow wire bond clearance, then wire bond integrity is maintained, but the optical path complexity increases and light extraction efficiency decreases
Solution Approach 1:
The patent moves the LED chip horizontally beneath the lens rather than positioning it vertically below the lens origin. This dimensional change in chip placement allows wire bonds to clear the lens area while maintaining optimal optical alignment, improving light extraction efficiency without compromising wire bond integrity
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 improved light extraction efficiency, reduced manufacturing complexity, and increased reliability by minimizing light loss and thermal stress, allowing for simpler secondary optics and more efficient heat management.
Implementation Method 1
covering at least part of the LED chip with a liquid encapsulant having a radius of curvature
Data Source
AI summary
A method for fabricating a light emitting diode (LED) package comprising providing an LED chip and covering at least part of the LED chip with a liquid encapsulant having a radius of curvature. An optical element is provided having a bottom surface with at least a portion having a radius of curvature larger than the liquid encapsulant. The larger radius of curvature portion of the optical element is brought into contact with the liquid encapsulant. The optical element is then moved closer to the LED chip, growing the contact area between said optical element and said liquid encapsulant. The liquid encapsulant is then cured. A light emitting diode comprising a substrate with an LED chip mounted to it. A meniscus ring is on the substrate around the LED chip with the meniscus ring having a meniscus holding feature. An inner encapsulant is provided over the LED chip with the inner encapsulant having a contacting surface on the substrate, with the meniscus holding feature which defines the edge of the contacting surface. An optical element is included having a bottom surface with at least a portion that is concave. The optical element is arranged on the substrate with the concave portion over the LED chip. A contacting encapsulant is included between the inner encapsulant and optical element.