Electrostatic Phosphor Spray for LED Uniformity
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Solution Overview
Problem
Conventional methods for coating LEDs with phosphor layers face challenges in controlling geometry and thickness, leading to non-uniform color temperature and reproducibility issues, particularly when using volumetric dispense, stencil printing, electrophoretic deposition, and droplet deposition techniques.
Innovation Solution
A method involving biasing a luminescent solution with a pressurized gas to atomize and spray it onto an LED structure, potentially applying a binder material and evaporating solvents to deposit wavelength conversion particles uniformly, with optional additional layers and encapsulation, using a system with controlled voltage biases and gas flow to ensure precise application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If volumetric dispense or stencil printing is used to apply phosphor, then the LED structure is covered with phosphor material, but the geometry and thickness of the phosphor layer cannot be controlled uniformly
Solution Approach 1:
The patent replaces conventional mechanical coating methods (volumetric dispense, stencil printing) with an electrostatic spray deposition system. The phosphor-containing composition is charged and deposited onto the LED structure through electrostatic attraction, allowing precise control of layer thickness and uniformity while eliminating the complexity of masks and manual dispensing operations.
Solution Approach 2:
The patent changes the physical state and electrical properties of the phosphor composition by suspending phosphor particles in a liquid carrier that can be charged. By controlling the electrical charge parameters and spray deposition conditions, the system achieves uniform phosphor layer thickness and geometry control that was not possible with conventional mechanical methods.
2Productivity
If multiple LEDs are arranged on a substrate for batch processing, then productivity increases, but controlling uniform phosphor application across all LEDs becomes more difficult
Solution Approach 1:
The electrostatic spray deposition system is designed to uniformly coat multiple LEDs simultaneously on a substrate. The charged phosphor composition is attracted to all LED structures in the array through electrostatic forces, providing consistent layer thickness and uniformity across all devices in a single batch processing operation, thereby maintaining high productivity with precise control.
3Manufacturing precision
If phosphor composition is deposited using conventional methods, then the LED is covered with phosphor, but the color temperature becomes non-uniform as a function of viewing angle
Solution Approach 1:
The patent replaces imprecise mechanical deposition methods with electrostatic spray deposition, which uses electrical fields to control phosphor particle distribution. This ensures uniform phosphor layer thickness across the entire LED surface, eliminating viewing angle-dependent color temperature variations and achieving consistent optical performance.
4Manufacturing precision
If stencil printing is used to apply phosphor, then the phosphor is deposited in the stencil openings, but the composition may not fully fill the openings and can stick to the stencil
Solution Approach 1:
The patent eliminates the stencil mechanism entirely by using electrostatic spray deposition. The charged phosphor composition is directly attracted to the LED structure, ensuring complete filling of the required areas without sticking to deposition tools. This eliminates phosphor waste from incomplete filling and stencil adhesion while achieving precise layer formation.
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 enables uniform and controlled application of phosphor layers, improving the reproducibility and consistency of LED emission characteristics, reducing waste and increasing the stability of the LED structure's light output.
Implementation Method 1
atomizing the luminescent solution using a flow of pressurized gas
Implementation Method 2
spraying the atomized luminescent solution onto the LED structure using the flow of pressurized gas
Implementation Method 3
biasing a luminescent solution including an optical material suspended in a solution at a first bias voltage level, mounting an LED structure on a stage, biasing the stage at a different voltage level than the first bias voltage level
Implementation Method 4
evaporating the solvent from the luminescent solution to provide a layer of wavelength conversion particles on the LED structure
Data Source
AI summary
Methods are disclosed including applying a layer of binder material onto an LED structure. A luminescent solution including an optical material suspended in a solution is atomized using a flow of pressurized gas, and the atomized luminescent solution is sprayed onto the LED structure including the layer of binder material using the flow of pressurized gas.