Ceramic LED Submount Structure for Light Extraction and Heat Flow
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Solution Overview
Problem
Conventional light-emitting diodes (LEDs) face challenges in maximizing light emission efficiency due to internal reflection, which leads to photons being absorbed rather than exiting the device, limiting their external quantum efficiency and light extraction.
Innovation Solution
The use of submount structures with a ceramic base and layers providing high thermal conductivity and reflectivity, including specific ceramic materials like alumina and zirconia toughened alumina, to enhance light reflection and redirect photons towards the desired emission direction, even in areas between tightly spaced electrical traces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional LED structures are used, then the device complexity is low, but the light extraction efficiency is limited due to internal reflection
Solution Approach 1:
The submount structure is segmented into multiple functional layers: a base material layer for thermal management, a first ceramic layer for electrical isolation and support, and a second ceramic layer specifically engineered for high reflectivity. This segmentation allows each layer to optimize its specific function, with the second ceramic layer capturing and redirecting internally reflected photons that would otherwise be lost, thereby improving light extraction efficiency without requiring complete redesign of the entire LED structure
Solution Approach 2:
The invention employs composite material construction by combining different ceramic materials with distinct properties. The first ceramic layer uses materials like alumina for electrical isolation and mechanical support, while the second ceramic layer uses materials with high reflectivity such as zirconia toughened alumina or barium sulfate. This composite approach allows the submount to simultaneously provide thermal conduction, electrical isolation, and enhanced optical reflection, resolving the contradiction between maintaining simple structure and improving light extraction
2Area of stationary object
If tightly spaced electrical traces are used, then the device area is reduced, but the reflectivity in gap areas decreases
Solution Approach 1:
The second ceramic layer is selectively applied in specific locations where electrical traces are spaced closely together and gaps would otherwise provide poor reflectivity. This local quality enhancement ensures that photons reflected toward trace gaps are captured and redirected toward the light extraction path. The layer is particularly positioned in these critical gap areas without requiring coverage of the entire submount surface, thus maintaining compact device area while improving light extraction efficiency in the most critical regions
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 increases the reflectivity of LED packages, improving light extraction and emission efficiency by redirecting internally reflected photons, thereby enhancing the overall light output and thermal management.
Implementation Method 1
a ceramic layer on the base material that is configured to provide high reflectivity for one or more LED chips that are mounted thereon
Implementation Method 2
a base material that is configured to provide high thermal conductivity
Data Source
AI summary
Submount structures for light-emitting diode (LED) packages are provided. Submounts may include a base material that is configured to provide high thermal conductivity and a ceramic layer on the base material that is configured to provide high reflectivity for one or more LED chips that are mounted thereon. In certain aspects, the base material may include a ceramic base having a ceramic material that is different than a material of the ceramic layer. In certain aspects, submounts may also include additional ceramic layers configured to provide high reflectivity. In certain aspects, LED packages include electrical traces that are arranged either on one or more ceramic layers or at least partially embedded within one or more ceramic layers. The arrangement of such ceramic layers may provide increased reflectivity in areas where it may be difficult for other reflective materials to be present, such as gaps formed between tightly spaced electrical traces.