Liquid Metal Reflective Member for LED Packaging
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Solution Overview
Problem
Current LED packaging technologies face issues such as optical degradation due to silver migration, reduced reflectivity at lower wavelengths, high material and process costs, and thermo-mechanical stresses, which affect light extraction efficiency and operational life.
Innovation Solution
A liquid metal reflective member with conductive and reflective properties, such as a eutectic Gallium-Indium mixture, is used in a recess on the substrate surface, encapsulated by a transparent cover, providing improved reflectivity and reduced thermo-mechanical stresses through a low-temperature bonding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a silver layer is used as a reflective layer, then reflectivity is improved, but optical degradation occurs due to silver migration and sulphide forming
Solution Approach 1:
The patent changes the material parameter of the reflective layer from silver to liquid metal (such as gallium or gallium-indium eutectic alloy). This material substitution eliminates the chemical degradation issues of silver while maintaining high reflectivity across a broad spectrum including lower wavelengths.
Solution Approach 2:
The patent employs a composite structure consisting of a liquid metal reflective layer combined with a transparent cover. This composite design provides both optical functionality (reflection) and protection against degradation, solving the reliability issue while maintaining reflectivity.
2Reliability
If conventional bonding processes are used, then electrical connection is achieved, but thermo-mechanical stresses are induced reducing operational life
Solution Approach 1:
The patent utilizes the phase transition property of liquid metal (melting point below operating temperature) to create a bonding process that occurs at lower temperatures. The liquid metal is applied in liquid state and solidifies upon cooling, forming reliable electrical and thermal connections without inducing excessive thermo-mechanical stresses.
Solution Approach 2:
The patent changes the temperature parameter of the bonding process by using liquid metal with low melting point. This allows bonding to occur at temperatures that minimize thermal expansion mismatches and reduce thermo-mechanical stresses on the LED chip and substrate.
3Ease of manufacture
If exposed wiring and electrodes are used for electrical connection, then electrical connection is achieved, but light extraction efficiency is decreased by light absorption
Solution Approach 1:
The patent makes the liquid metal serve multiple functions simultaneously: it acts as the reflective layer for optical enhancement, as the electrode for electrical connection, and as a protective covering for the wiring. This multi-functionality eliminates the need for separate exposed wiring while maintaining both electrical connectivity and light extraction efficiency.
Solution Approach 2:
The patent extracts the harmful light-absorbing wiring from the optical path by encasing it within the liquid metal reflective layer. The wiring remains functional for electrical connection but is optically isolated, preventing it from absorbing light that should be extracted from the LED.
4Illumination intensity
If high reflectivity is achieved using traditional materials, then light output is optimized, but material costs and process steps remain substantial
Solution Approach 1:
The patent changes the material parameter to liquid metal, which can be applied in liquid state and then solidifies, simplifying the deposition process. This eliminates the need for complex vacuum deposition or sputtering processes required for traditional reflective coatings, reducing both material costs and process complexity.
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 solution enhances reflective properties, reduces optical degradation, and lowers manufacturing and operational costs by minimizing thermo-mechanical stresses and process complexity, while allowing for flexible packaging designs and improved light extraction efficiency.
Implementation Method 1
a reflective member, said reflective member being disposed on the substrate surface in optical correspondence with the electro-optical element, so as to reflect electromagnetic radiation to or from the electro-optical element via said reflective member when in use
Implementation Method 2
The reflective member is formed of a metal that is in liquid state when in use
Implementation Method 3
The reflective member is contained in a recess provided in or on the substrate surface having a transparent cover covering said recess
Data Source
AI summary
According to an aspect of the invention, there is provided an electro-optical device comprising: an electro-optical element having electric terminals and a support for supporting said electro-optical element, said support comprising a substrate, at least an electrode for electrical connection to an electric terminal of the electro-optical element, and a reflective member, said reflective member being disposed on the substrate surface over a perimeter of the electro-optical element, so as to reflect electromagnetic radiation to or from the electro-optical element via said reflective member when in use. The reflective member is contained in a recess provided in or on the substrate surface having a transparent cover covering said recess. The reflective member is formed of a metal that is in liquid state when in use. Advantages may include improved reflective properties and less optical degradation.