Solid State Bidirectional Light Sheet Thermal Management
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Solution Overview
Problem
Existing solid state light sheets for general illumination face challenges such as heat management, optical uniformity, cost-effectiveness, and reliability due to high power consumption, complex packaging, and inefficiencies in light distribution, particularly when trying to replace traditional fluorescent lighting.
Innovation Solution
A flexible light sheet design featuring a conductor pattern on a bottom substrate with metal vias for heat sinking, a reflective and dielectric-coated aluminum layer for thermal management and light distribution, and an intermediate sheet with phosphor-filled holes for uniform light emission, using low power LEDs to achieve a cost-effective and aesthetically pleasing illumination solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If high power LEDs are used to achieve high lumen output, then illumination intensity is improved, but heat generation increases and packaging complexity increases
Solution Approach 1:
The patent divides the light source into multiple low power LED dice (e.g., 100-1000 dice) distributed across the light sheet rather than using fewer high power LEDs. This segmentation reduces heat generation per unit area while maintaining total lumen output, and eliminates the need for complex high-power LED packaging.
Solution Approach 2:
The patent extracts the heat management function from the LED packaging by using thin substrate sheets that allow heat to dissipate to both sides of the light sheet. This extraction simplifies the packaging structure while effectively managing thermal loads from the distributed LED array.
2Illumination intensity
If high power LEDs are used to achieve high lumen output, then illumination intensity is improved, but device complexity increases
Solution Approach 1:
The patent segments the light source into numerous low power LED dice mounted on thin substrate sheets, eliminating the need for complex high-power LED packaging structures while achieving the same or higher total lumen output.
Solution Approach 2:
The thin substrate sheets serve multiple functions: they provide mechanical support for the LED dice, conduct heat away from the LEDs, and allow light emission from both sides of the sheet. This multi-functionality reduces overall device complexity compared to specialized high-power LED packages.
3Illumination intensity
If conventional LED arrays are used, then illumination is provided, but optical uniformity deteriorates due to point source emission
Solution Approach 1:
The patent segments the light source into many small LED dice distributed across the light sheet, transforming the emission pattern from concentrated point sources to a distributed array. This segmentation creates a more uniform optical output across the entire light sheet area.
Solution Approach 2:
The patent transitions from conventional single-sided LED emission to bidirectional emission by mounting LEDs on thin substrates that allow light to escape from both sides. This dimensional change in light emission improves optical uniformity by distributing light across multiple spatial dimensions.
4Use of energy by moving object
If traditional fluorescent lighting is replaced with solid state lighting, then energy efficiency is improved, but cost-effectiveness deteriorates due to high component costs
Solution Approach 1:
The patent uses inexpensive low power LED dice that can be mass-produced at low cost, replacing expensive high-power LED packages. While individual LEDs have lower output, the sheer number of cheap LEDs used in the array achieves comparable total lumen output at lower overall cost.
Solution Approach 2:
The patent divides the lighting function across many low-cost LED dice rather than relying on a few expensive high-power LEDs, achieving cost-effectiveness through numbers while maintaining energy efficiency of solid state lighting.
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 provides a cost-effective, reliable, and optically uniform light source that can replace traditional fluorescent lighting, offering improved heat management and efficient light distribution while being modular and energy-efficient.
Implementation Method 1
a reflective and dielectric-coated aluminum layer for thermal management
Implementation Method 2
a reflective and dielectric-coated aluminum layer for thermal management and light distribution
Implementation Method 3
an intermediate sheet with phosphor-filled holes for uniform light emission
Data Source
AI summary
A solid state light sheet and method of fabricating the sheet are disclosed. In one embodiment, bare LED chips have top and bottom electrodes, where the bottom electrode is a large reflective electrode. The bottom electrodes of an array of LEDs (e.g., 500 LEDs) are bonded to an array of electrodes formed on a flexible bottom substrate. Conductive traces are formed on the bottom substrate connected to the electrodes. A transparent top substrate having conductors is then laminated over the bottom substrate. Various ways to connect the LEDs in series are described along with many embodiments. The light sheets may be formed to emit light from opposite surfaces of the light sheet, enabling it to be used in a hanging fixture to illuminate the ceiling as well as the floor. The light sheet provides a practical substitute for a standard 2×4 foot fluorescent ceiling fixture.