LED Cup Reflective Coating Thermal Management
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Solution Overview
Problem
High junction temperatures in LED devices cause degradation of plastic housings and reduce reflectivity of white reflective sidewalls, leading to decreased light output over time.
Innovation Solution
A light emitting device design featuring a cup with a reflective inner surface, supported by a housing, which maintains a gap from the substrate to prevent electrical contact and includes a highly-reflective metal coating to maximize light output while managing heat.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If white reflective sidewalls are used in plastic housing to increase light output, then light output is improved, but heat causes the sidewalls to turn yellow and reduce reflectivity over time
Solution Approach 1:
The patent replaces the durable but heat-sensitive white plastic reflective sidewalls with a thin, replaceable metallic reflective coating applied to the cavity surface. This coating can be reapplied or replaced if it degrades, solving the reliability issue while maintaining high reflectivity for light output enhancement.
Solution Approach 2:
The patent changes the material parameter of the reflective surface from white plastic to metallic coating, which has superior heat resistance and maintainable reflectivity properties. This parameter change allows the surface to withstand high junction temperatures without turning yellow and losing reflectivity.
2Illumination intensity
If the cup is positioned close to the substrate to maximize light reflection, then light output is improved, but electrical contact between the cup and substrate may occur
Solution Approach 1:
The patent introduces an insulating layer or design feature between the conductive cup and the substrate that prevents electrical contact while allowing the cup to remain positioned close to the substrate for optimal light reflection. This intermediary element resolves the conflict between maximizing light output and preventing harmful electrical contact.
3Power
If high junction temperatures are allowed to occur during LED operation, then power output is improved, but the plastic housing degrades quickly
Solution Approach 1:
The patent extracts the heat-sensitive plastic housing material from the critical reflective surface area and replaces it with a heat-resistant metallic coating. This allows the LED to operate at high junction temperatures for improved power output while the heat-resistant coating protects against thermal degradation, extending the effective lifespan of the housing structure.
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 effectively maintains high brightness and consistent light output by preventing heat-induced degradation of the reflective surfaces, ensuring prolonged performance of the LED device.
Implementation Method 1
A light emitting device includes a cup with a reflective inner surface that surrounds a light emitting die
Data Source
AI summary
A light emitting device is disclosed herein which includes a substrate, a housing, a light emitting die, and a cup with a reflective inner surface. The housing has an upper surface and at least one sidewall and is mounted on the upper surface of the substrate, thereby forming a cavity. The light emitting die is mounted on the upper surface of the substrate within the cavity. The cup is positioned within the cavity and is supported by the housing. The cup has a continuous sidewall with a reflective inner surface surrounding the light emitting die and a lowermost edge that is suspended above, detached and spaced away from the upper surface of the substrate.