LED Light Emitting Device Thermal Management via Phosphor Adhesive
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Solution Overview
Problem
Conventional light-emitting devices with phosphors suffer from thermal quenching due to heat generation, leading to reduced luminous efficiency and variations in emission color, especially in high-brightness applications like projectors, where efficient heat dissipation is challenging due to low thermal conductivity of synthetic resin covers and the absence of effective heat dissipating members.
Innovation Solution
A light-emitting device design incorporating a phosphor layer with high thermal conductivity materials like single crystal phosphors, ceramic phosphors, or glass with phosphor particles, directly connected to a heat dissipating member via an adhesive layer with enhanced thermal conductivity, ensuring efficient heat transfer and minimal temperature rise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cover formed of synthetic resin mixed with phosphor is used to protect the light-emitting diode, then the device is less likely to cause deterioration due to light or heat, but the thermal conductivity is low making it difficult to efficiently transfer heat generated by the phosphor
Solution Approach 1:
The device is divided into distinct functional regions: a protection unit with the synthetic resin cover containing phosphor, and a heat dissipation unit with high thermal conductivity members. This segmentation allows each part to perform its specialized function optimally - the resin cover provides protection and phosphor conversion, while the separate heat dissipation structure efficiently manages thermal energy.
Solution Approach 2:
A heat dissipating member with high thermal conductivity is introduced as an intermediary between the phosphor and the external environment. This intermediary component facilitates efficient heat transfer from the phosphor without requiring the protective cover material itself to have high thermal conductivity, thus resolving the contradiction between protection and heat dissipation.
2Duration of action of stationary object
If the phosphor is positioned away from the light-emitting diode to reduce deterioration, then the device has a long life, but heat generated by the phosphor cannot be efficiently transferred to peripheral portions
Solution Approach 1:
The heat dissipation approach transitions from relying on lateral heat transfer through the phosphor-containing resin cover to utilizing a vertical/dedicated heat dissipation path through high thermal conductivity members. This dimensional change in heat transfer strategy allows the phosphor to be positioned for optimal protection while heat is efficiently removed through a specialized pathway.
3Illumination intensity
If high brightness and high light intensity are required for lighting apparatus such as projectors, then the phosphor temperature rise becomes significant, but the low thermal conductivity of the synthetic resin cover prevents effective heat dissipation
Solution Approach 1:
The thermal conductivity parameter of the heat dissipation system is significantly changed by introducing high thermal conductivity members (such as metals or ceramic materials) compared to the original synthetic resin cover. This parameter change enables effective heat dissipation even under high brightness conditions where substantial heat is generated by the phosphor.
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 design effectively dissipates heat, maintaining high luminous efficiency and stability in emission color, even under high-brightness conditions, by utilizing materials with higher thermal conductivity to manage thermal quenching and ensure reliable performance in lighting applications.
Implementation Method 1
a phosphor layer that is operable to convert a wavelength of the light emitted from the light-emitting element
Implementation Method 2
a heat dissipating member that dissipates heat generated in the phosphor layer
Data Source
AI summary
According to one embodiment of the present invention, the light emitting device includes an LED element, a side wall which surrounds the LED element, a phosphor layer which is fixed to the side wall with an adhesive layer therebetween, and is positioned above the LED element, and a metal pad as a heat dissipating member. The side wall includes an insulating base which surrounds the LED element and a metal layer which is formed on a side surface at the LED element side of the base, and is in contact with the metal pad and the adhesive layer. The adhesive layer includes a resin layer that includes a resin containing particles which have higher thermal conductivity than the resin or a layer that includes solder.