LED Package Lens Cavity for High-Current Heat Dissipation
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Solution Overview
Problem
Conventional LED packages face challenges in achieving high light emission efficiency due to internal reflection and mechanical strain caused by differences in thermal expansion coefficients between encapsulant materials and LED chips, limiting their ability to operate at higher drive currents without degradation.
Innovation Solution
The design of an LED package with a lens forming a cavity around the LED chips without direct encapsulation, allowing for higher drive currents and improved heat dissipation through air flow between the cavity and the ambient environment, using spacers to support the lens and reduce mechanical strain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If encapsulant materials are used to surround and contact the LED chips, then mechanical support and protection are provided, but mechanical strain and degradation occur due to differences in coefficients of thermal expansion
Solution Approach 1:
The patent removes the encapsulant material that directly contacts the LED chips, extracting the source of mechanical strain caused by thermal expansion coefficient mismatches. The LED chips are mounted on a submount without being surrounded by encapsulant, eliminating the mechanical strain and degradation issues while maintaining structural integrity through the submount and lens assembly.
2Productivity
If higher drive currents are used to increase light output, then luminous flux is improved, but heat generation increases causing degradation and mechanical strain
Solution Approach 1:
The patent extracts the encapsulant material that traps heat around the LED chips, allowing for superior heat dissipation. By mounting chips directly on the submount without encapsulant surrounding them, heat can be more effectively conducted away from the chips through the submount to heat sinks, enabling higher drive currents without thermal degradation.
3Object-affected harmful factors
If encapsulation is used to protect LED chips and wirebonds, then environmental protection is provided, but light extraction efficiency is reduced due to internal reflection
Solution Approach 1:
The patent removes the encapsulant material that causes internal reflection and reduces light extraction efficiency. LED chips are mounted on the submount without encapsulant surrounding them, maximizing light output. Environmental protection is maintained through the lens assembly and package structure rather than through encapsulation of the chips themselves.
Solution Approach 2:
The patent introduces a lens as an intermediary optical element that focuses and directs light from the LED chips. The lens is positioned to receive light directly from the chips without encapsulant interference, and optically couples the chips to external environments, improving light extraction efficiency while maintaining environmental protection.
4Volume of moving object
If smaller package sizes are used for higher light output applications, then compactness is improved, but heat dissipation and light extraction become more challenging
Solution Approach 1:
The patent removes the encapsulant material that occupies volume and traps heat, enabling more efficient heat dissipation in compact packages. The direct-mount configuration without encapsulant allows for better thermal management in smaller form factors.
Solution Approach 2:
The lens serves as an optical intermediary that efficiently couples light from the small LED chips to external spaces, maximizing light extraction from compact packages. The lens assembly optimizes the optical path to overcome the limitations of small package sizes.
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 enhances light extraction efficiency and reduces mechanical strain, enabling LED packages to operate at higher drive currents with reduced degradation and improved heat dissipation.
Implementation Method 1
allow air flow between an interior volume of a cavity and an ambient environment outside the LED package to promote further heat dissipation
Implementation Method 2
When a bias is applied across the doped layers, holes and electrons are injected into the one or more active layers where they recombine to generate emissions such as visible light or ultraviolet emissions
Implementation Method 3
According to the well-understood implications of Snell's law, photons reaching the surface (interface) between an LED surface and the surrounding environment are either refracted or internally reflected
Implementation Method 4
If photons are internally reflected in a repeated manner, then such photons eventually are absorbed and never provide visible light that exits an LED
Data Source
AI summary
Solid-state lighting devices including light-emitting diodes (LEDs) and lens arrangements for packaged LED devices are disclosed. An LED package may include one or more LED chips on a submount with a lens positioned on the submount to form a cavity. The one or more LED chips may reside in the cavity without direct encapsulation materials that would otherwise contact the one or more LED chips and any corresponding wirebonds. In this manner, the one or more LED chips may be driven with higher drive currents while reducing degradation and mechanical strain effects related to differences in coefficients of thermal expansion with typical encapsulant materials. LED packages may also be configured with one or more apertures that allow air flow between an interior volume of a cavity and an ambient environment outside the LED package to promote heat dissipation at higher drive currents.