Stencil-Based Phosphor Deposition for LED Chips
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Solution Overview
Problem
Conventional methods for applying phosphor to LED chips are inefficient in terms of conversion efficiency and phosphor usage, with conformal coating methods wasting phosphor and mini-glob methods not achieving optimal color temperature and conversion efficiency simultaneously.
Innovation Solution
A method involving a stencil to accurately deposit phosphor-containing material on LED chips, allowing for a densely packed layer of phosphor particles on the light emitting surfaces, which is then cured, enhancing light conversion efficiency and heat transfer while minimizing phosphor usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If conformal coating method is used to apply phosphor to LED chip, then the light emitting surface is uniformly covered, but phosphor is wasted and conversion efficiency is reduced
Solution Approach 1:
The stencil is designed with openings that precisely match the geometry of the light emitting surface, allowing phosphor to be deposited only where needed. This localized deposition approach ensures uniform coverage of the light emitting surface while preventing phosphor waste on surrounding areas, directly resolving the contradiction between uniform coverage and phosphor waste.
2Loss of substance
If mini-glob method is used to apply phosphor, then phosphor usage is reduced, but color temperature and conversion efficiency are not optimal
Solution Approach 1:
The manual or semi-automatic mini-glob application process is replaced with a stencil-based deposition system that uses precise mechanical positioning and controlled material flow. This substitution enables accurate control of phosphor layer thickness and uniformity, achieving optimal color temperature and conversion efficiency while maintaining efficient phosphor usage.
3Loss of energy
If thicker phosphor layer is applied to improve conversion efficiency, then more light is converted, but heat transfer becomes less efficient
Solution Approach 1:
The stencil enables precise control of the phosphor layer thickness parameter, allowing optimization of the trade-off between light conversion efficiency and heat transfer. By controlling the layer to be sufficiently thin while maintaining uniform coverage, the design achieves adequate light conversion while ensuring that heat can effectively transfer from the phosphor layer to the LED chip substrate.
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 approach improves light conversion efficiency and reduces phosphor usage, achieving better color temperature and conversion efficiency while maintaining chip integrity and facilitating further processing.
Implementation Method 1
The phosphor particles convert light emitted by the one or more light emitting surfaces to light having a second dominant wavelength different from the first dominant wavelength
Implementation Method 2
light is emitted by a phosphor when a photon having energy higher than a bandgap of the phosphor material passes through the phosphor and is absorbed
Implementation Method 3
enhancing light conversion efficiency and heat transfer
Data Source
AI summary
A method of making a semiconductor light emitting device having one or more light emitting surfaces includes positioning a stencil on a substrate such that a chip disposed on the substrate is positioned within an opening in the stencil. Phosphor-containing material is deposited in the opening to form a coating on one or more light emitting surfaces of the chip. The opening may or may not substantially conform to a shape of the chip. The phosphor-containing material is cured with the stencil still in place. After curing, the stencil is removed from the substrate and the coated chip is separated from the substrate. The chip may then be subjected to further processing.