Light Emitting Device Spacing Thermal Management
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Solution Overview
Problem
Maintaining the optimal distance between a luminescent element and a cooling element in light emitting devices is challenging, as it affects both light loss and thermal resistance, making it difficult to prevent evanescent wave-induced light losses while minimizing thermal resistance in industrial environments.
Innovation Solution
A light emitting device with a luminescent element and a cooling element spaced apart by spacer elements, where the cooling element is compliant to follow warpage and a force is applied to maintain a consistent distance without direct contact, using a combination of surface structures and separate spacer elements like nanospheres, and a force application device to ensure optimal thermal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the distance between the luminescent element and the cooling element is increased to prevent evanescent wave-induced light losses, then light loss is reduced, but thermal resistance increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the distance parameter between the luminescent element and cooling element to fall within the range of 1-5 μm. This specific parameter range optimizes the balance between preventing evanescent wave light losses (which occur at larger distances) and minimizing thermal resistance (which increases at larger distances), thereby resolving the technical contradiction between light loss and thermal resistance.
Solution Approach 2:
The patent employs local quality by applying different surface treatments to different parts of the cooling element. Specifically, the surface facing the luminescent element is made highly reflective (with reflectivity >95% in the blue wavelength range) to prevent light losses, while other surfaces can have different properties for heat dissipation. This localized differentiation allows the system to simultaneously address both light loss prevention and thermal management.
2Temperature
If the distance between the luminescent element and the cooling element is precisely controlled to optimize thermal management, then thermal resistance is minimized, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies preliminary action by pre-forming spacer structures (such as protrusions or raised features) on the cooling element surface before final assembly. These spacers are integrated into the cooling element manufacturing process, establishing the precise 1-5 μm gap distance in advance. This preliminary structuring eliminates the need for post-assembly distance adjustment and ensures consistent spacing without requiring extreme manufacturing precision during final assembly.
Solution Approach 2:
The patent uses an intermediary approach by introducing physical spacer structures (protrusions or raised features) between the luminescent element and cooling element. These spacers act as mechanical intermediaries that automatically maintain the optimal 1-5 μm distance, transferring the precision requirement from the final assembly process to the spacer manufacturing process, which can be more easily controlled.
3Stability of the object's composition
If the cooling element is made rigid to ensure structural stability, then structural stability is improved, but adaptability to luminescent element warpage decreases
Solution Approach 1:
The patent applies segmentation by dividing the cooling element into multiple independent cooling segments or sections along its length. Each segment can independently deflect or adapt to local warpage of the luminescent element while maintaining overall structural stability. This segmentation allows the cooling element to accommodate dimensional changes and warpage without compromising its ability to maintain the optimal 1-5 μm gap distance across the entire surface.
Solution Approach 2:
The patent employs dynamics by designing the cooling element with controlled flexibility or compliance in specific directions. The cooling element can dynamically adjust its shape to follow luminescent element warpage while maintaining rigid thermal contact. This dynamic adaptability ensures continuous optimal spacing even when the luminescent element undergoes thermal expansion or manufacturing-induced warpage.
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 maintains the correct distance to prevent light losses while minimizing thermal resistance, ensuring efficient cooling and robustness, and simplifies maintenance in industrial settings by allowing for a durable and cost-effective design with reduced light losses.
Implementation Method 1
The conversion of the blue light into light of longer wavelengths is, due to Stokes shift, associated with heat generation. The heat has to be transported out of the luminescent element while maintaining the TIR for the light.
Implementation Method 2
Polished, elongated rectangular luminescent elements being irradiated by blue light from LEDs are well known within the field of light emitting devices. Within such a luminescent element, the blue light is converted into green or red light.
Implementation Method 3
The conversion of the blue light into light of longer wavelengths is, due to Stokes shift, associated with heat generation.
Implementation Method 4
Photons within a certain directional cone will experience total internal reflection (TIR) by the sides of the luminescent element, and will propagate to the exit window
Data Source
Figure 1~2
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AI summary
A light emitting device (1) comprising a luminescent element (2) comprising a first surface (21), at least one cooling element (3) arranged at the first surface of the luminescent element, and a plurality of spacer elements (5) arranged between the cooling element (3) and the first surface (21) of the luminescent element such that the cooling element is arranged spaced apart from the first surface of the luminescent element with a distance, d. The at least one cooling element (3) comprises a compliance such as to be adapted for following warpage of the luminescent element (2) induced by any one or more of clamping forces, forces inflicted by production processes and light and/or heat propagating within the luminescent element, and a force (F) is applied to force the at least one cooling element (3) and the luminescent element (2) together in such a way that no part of the at least one cooling element and the luminescent element are in direct mutual contact.