LED Package Lens Adhesive Thermal Expansion Compensation
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Solution Overview
Problem
Conventional LED packages face challenges in generating white light, require complex fabrication and control electronics, and suffer from wavelength degradation and thermal expansion mismatches that can lead to delamination and cracking, affecting light extraction and reliability.
Innovation Solution
A substrate-based LED package design featuring a dispensed optical lens made from harder materials than the encapsulant, with a meniscus holding feature to form a hemispherical shape, and an adhesive to compensate for thermal expansion mismatches, eliminating the need for separate lenses and enhancing light extraction and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a separate glass lens is used to enhance light extraction, then light extraction is improved, but device complexity increases and manufacturing cost increases
Solution Approach 1:
The patent combines the lens function with the encapsulant material itself, eliminating the need for a separate lens component. The encapsulant is formulated with optical properties (refractive index, transparency) that enable it to function as both protective coating and light-extraction enhancement element, merging two functions into one material system.
Solution Approach 2:
The encapsulant material is designed to perform multiple functions simultaneously: mechanical protection of the LED chip, chemical protection from environmental degradation, optical enhancement of light extraction, and thermal management. This multi-functional design eliminates the need for separate specialized components.
2Illumination intensity
If a separate molded silicone lens is used to enhance light extraction, then light extraction is improved, but device complexity increases and manufacturing cost increases
Solution Approach 1:
The patent integrates the lens functionality directly into the encapsulant material, eliminating the need for a separate molded lens component. The encapsulant's optical properties are engineered to provide light extraction enhancement without requiring additional piece parts.
Solution Approach 2:
The encapsulant material serves multiple purposes: structural protection, environmental sealing, optical enhancement, and thermal management. By making the encapsulant multi-functional, the patent eliminates the need for separate lens and protective components.
3Illumination intensity
If different materials with different CTE are used for lens and package components, then optical performance is improved, but reliability deteriorates due to cracking and delamination
Solution Approach 1:
The patent uses the same material for both the encapsulant and lens functions, ensuring uniform coefficients of thermal expansion throughout the optical system. This material homogeneity eliminates CTE mismatch stresses that would otherwise cause cracking, delamination, or wire bond failure during thermal cycling.
Solution Approach 2:
The patent employs a composite encapsulant material that combines the mechanical properties needed for protection with optimized optical properties for light extraction enhancement. This single composite material provides both structural and optical functionality while maintaining thermal expansion compatibility.
4Adaptability or versatility
If conventional LED packages use multiple separate components, then functionality is improved, but ease of manufacture deteriorates
Solution Approach 1:
The patent combines multiple functional components (protective coating, optical lens, sealing element) into a single integrated encapsulant structure. This reduces the number of assembly steps, eliminates the need for separate component attachment, and simplifies the manufacturing process while maintaining all necessary functions.
Solution Approach 2:
The encapsulant material is designed to perform multiple functions simultaneously - protection, optical enhancement, and sealing - which eliminates the need for multiple separate components and their associated assembly operations, thereby improving ease of manufacture.
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
The solution allows for efficient light extraction, improved thermal stability, and reduced failure rates by using a compatible silicone encapsulant and adhesive, enabling the production of reliable LED packages with reproducible optical elements without additional piece parts.
Implementation Method 1
compensating for different coefficients of thermal expansion (CTE) between the lens the remainder of the package
Implementation Method 2
a nitride based blue emitting LED chip can be surrounded by a yellow phosphor. Some of the blue light will pass through the phosphor without being changed while the remaining light will be downconverted to yellow
Implementation Method 3
an optical element such as a simple hemispherical lens is also desired to enhance light extraction from the package
Data Source
AI summary
A light emitting diode (LED) package comprising a substrate with an LED chip mounted to the substrate and in electrical contact with it. An inner material covers the LED chip, and a lens covers the inner material with the lens material being harder than the inner material. An adhesive is arranged between the substrate and the lens to hold the lens to the substrate and to compensate for different coefficients of thermal expansion (CTE) between the lens and the remainder of the package. A method for forming an LED package comprises providing a substrate with a first meniscus ring on a surface of the substrate. An LED chip is mounted to the substrate, within the meniscus ring. An inner material is deposited over the LED chip, and a lens material in liquid form is deposited over the inner material. The lens material held in a hemispheric shape by the first meniscus feature and the lens material is cured making it harder than the inner material.