LED Package Expansion Volume Prevents Encapsulant Delamination
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Solution Overview
Problem
Light-emitting device packages face issues with encapsulant delamination due to thermal expansion mismatch between materials, leading to residual stress and reduced light intensity, especially when using phosphor-coated or filled light-transmissive covers that generate heat, causing efficiency decreases and potential overheating.
Innovation Solution
Incorporating an expansion volume within the package to allow the encapsulant to flow into and out of during thermal expansion and contraction, relieving internal stresses, and using thermally conductive materials to manage heat transfer from the phosphor-coated cover to the substrate, ensuring efficient heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phosphor-coated or filled light-transmissive covers are used to convert light wavelength, then light conversion efficiency is improved, but heat generation increases causing temperature rise and potential overheating
Solution Approach 1:
The patent extracts the phosphor coating from the light-transmissive cover and places it directly on the LED die. This separation allows the cover to focus on light transmission while the phosphor converts light at the source, reducing heat accumulation in the cover and improving thermal management
Solution Approach 2:
The patent introduces a specialized phosphor attachment layer as an intermediary between the LED die and the light-transmissive cover. This layer enables efficient light conversion while providing a thermal pathway that prevents excessive heat buildup in the cover structure
2Adaptability or versatility
If materials with different thermal expansion coefficients are used in the package, then design flexibility is improved, but thermal expansion mismatch causes residual stress and encapsulant delamination
Solution Approach 1:
The patent applies different material properties to different regions of the package. The substrate uses materials optimized for thermal management while the encapsulant and cover use materials optimized for light transmission and stress resistance, with transition layers that gradually change material properties to reduce stress concentration
Solution Approach 2:
The patent modifies material selection and structural parameters to account for thermal expansion differences. This includes selecting materials with compatible thermal expansion coefficients for critical interfaces, designing compensation structures, and adjusting geometric parameters to accommodate thermal cycling without causing delamination
3Temperature
If heat dissipation is improved by using thermally conductive materials, then temperature management is improved, but light extraction efficiency may be affected due to material selection constraints
Solution Approach 1:
The patent divides the package into distinct functional zones with specialized materials: a thermally conductive substrate for heat dissipation, an optically optimized encapsulant for light extraction, and a phosphor attachment layer for wavelength conversion. This segmentation allows each component to be optimized for its primary function without compromising overall performance
Solution Approach 2:
The patent employs composite material structures that combine thermal and optical properties. The substrate uses composite materials with high thermal conductivity and appropriate mechanical properties, while the encapsulant uses materials that balance optical transparency with thermal management capabilities, achieving both heat dissipation and light extraction efficiency
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 configuration reduces the likelihood of encapsulant delamination, enhances the reliability and light extraction efficiency of the LED package by managing thermal stresses and maintaining optimal operating temperatures.
Implementation Method 1
A substantially flat substrate in addition to being a mechanical support is often used as a means for heat dissipation from the light-emitting device. When used in the latter function the substrate is made from a material with high thermal conductivity.
Implementation Method 2
The support member 108 provides boundary for an encapsulant 110 and reflects light emitted by the die or dice 114 into desirable direction.
Implementation Method 3
an encapsulant is applied into a cavity surrounding the light-emitting region. The material for the encapsulant is selected to moderate the differences between the refraction indexes of the materials from which components creating the reflective boundaries are made.
Implementation Method 4
Different windows or lenses may have different phosphor coatings or fillings, and these matched with LED die or dice of optimal wavelength to achieve target CCT as needed.
Data Source
AI summary
A sub-assembly of a light-emitting device package and/or a light-emitting device package, the package comprising a cavity filled with an encapsulant, are disclosed with means preventing the encapsulant delamination. The means comprise an expansion volume within the light-emitting device package, together with means allowing the encapsulant to flow from the cavity into the expansion volume as the encapsulant expands, and to flow back into the cavity as the encapsulant contracts during heating and cooling of the light-emitting device package.