Side-Held Wavelength Converting Element for LED Thermal Stress Reduction
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Solution Overview
Problem
Conventional illumination devices with phosphors in physical contact with LEDs face limitations due to a limited bonding temperature range and thermally induced mechanical stress, which affect cost and reliability.
Innovation Solution
An illumination device design where a wavelength converting element, such as a luminescent ceramic, is physically separated from the light source and held by a heat sink, with a color separation element directly coated on the wavelength converting element to recycle backward emitted light and improve extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the phosphor is placed in physical contact with the LED, then the wavelength conversion is efficient, but the bonding temperature range is limited and thermally induced mechanical stress increases
Solution Approach 1:
The device separates the wavelength converting element from the light source, placing them at different locations along the light path. This segmentation allows the LED and phosphor to operate independently at their optimal temperatures, eliminating thermal stress from direct bonding while maintaining conversion efficiency through optical coupling
Solution Approach 2:
An intermediary optical system is introduced between the LED and wavelength converting element to transfer light energy. This mediator allows efficient wavelength conversion without requiring direct physical contact, thereby avoiding the thermal and mechanical stress problems associated with direct bonding
2Strength
If bonding material is used to attach the wavelength converting element to the LED, then the components are securely connected, but the cost increases and reliability is reduced due to thermally induced mechanical stress
Solution Approach 1:
The bonding material is completely removed from the system by separating the wavelength converting element from the LED. The elements are held in position by mechanical structures (mounts, clips, or frames) rather than thermal bonding, eliminating the need for additional materials and reducing overall device complexity
Solution Approach 2:
The invention uses simple, inexpensive mechanical holding structures instead of expensive, specialized bonding materials. These mechanical fixtures can be easily manufactured and replaced if needed, reducing both material cost and manufacturing complexity
3Reliability
If additional optical elements and bonding materials are used, then the assembly is more complete, but the cost increases
Solution Approach 1:
The holding structure for the wavelength converting element is merged with the heat sink or mounting fixture, eliminating the need for separate bonding materials. This integration maintains assembly completeness while reducing the number of components and manufacturing steps
Solution Approach 2:
The heat sink or mounting structure serves multiple functions: it provides mechanical support, thermal management, and positioning for the wavelength converting element. This multi-functionality eliminates the need for additional specialized components, reducing overall manufacturing cost
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 design enhances extraction efficiency, reduces thermal stress, and lowers costs by eliminating the need for additional optical elements and bonding materials, while maintaining effective color conversion and aperture recycling.
Implementation Method 1
LEDs use phosphor conversion of the primary emission to generate white light, but phosphors can also be used to create more saturated colors like red, green and yellow
Implementation Method 2
the wavelength converting element is held by a heat sink by at least one side
Data Source
Figure 1~3
Figure 2
Figure 4~6
AI summary
An illumination device (100) includes a light source (104), such as one or more light emitting diodes in an array, that produces light having a first wavelength range. A separated wavelength converting element (110) is mounted to receive the light emitted by the light source (104). The wavelength converting element (110) is physically separated from the light source (104) along the beam path. The wavelength converting element (110) converts the light having a first wavelength range into light having a second wavelength range. In one embodiment, a color separation element (112) is directly coupled to the wavelength converting element. The color separation element (112) is also physically separated from the light source (104). In another embodiment, the wavelength converting element (110) is held by a heat sink (130) by the sides.