Closed-Loop Electrophoretic Deposition for LED Phosphor Uniformity

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Solution Overview

Problem

Conventional methods for coating LEDs with phosphor materials, such as syringe injection and stencil printing, face challenges in controlling the geometry and thickness of the phosphor layer, leading to non-uniform color temperature and inconsistent emission characteristics due to difficulties in achieving uniform deposition.

Innovation Solution

A close-loop electrophoretic deposition system that seals the semiconductor devices and deposition mixture from ambient air, using a voltage supply to deposit a uniform layer of conversion material, including phosphors, onto the LEDs, ensuring repeatable and contamination-free deposition.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If syringe or nozzle method is used for injecting phosphor containing epoxy or resin, then the LED can be coated with phosphor material, but the geometry and thickness of the phosphor layer cannot be controlled uniformly

Engineering Contradiction:

Improvephosphor layer thickness uniformityVSAvoiddeposition process control

Core Design Contradiction:

Manufacturing precisionVSEase of operation

Solution Approach 1:

The patent replaces mechanical injection methods (syringe/nozzle) with electrophoretic deposition using an electric field. The phosphor particles are suspended in an electrolyte solution and deposited onto the LED chip through application of voltage, enabling uniform thickness control without mechanical positioning difficulties.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the deposition mechanism from mechanical injection to electrophoretic movement by altering the physical state of the phosphor delivery system - using suspended particles in electrolyte solution that respond to electric field parameters (voltage, time) rather than mechanical injection parameters.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If stencil printing method is used for coating LED with phosphor, then multiple LEDs can be processed, but the geometry and layer thickness remain difficult to control

Engineering Contradiction:

Improvebatch processing capabilityVSAvoidphosphor layer thickness uniformity

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent replaces the mechanical stencil printing process with electrophoretic deposition. Instead of using a physical stencil mask that is difficult to align and maintain, the electric field uniformly distributes phosphor particles across all LED chips in the batch, achieving both high productivity and precise thickness control.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Manufacturing precision

If conventional coating methods are used, then phosphor can be deposited on LED, but non-uniform color temperature results due to varying light path through conversion material

Engineering Contradiction:

Improvecolor temperature uniformityVSAvoidemission characteristic consistency

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent uses electrophoretic deposition to replace conventional coating methods, creating uniformly thick phosphor layers through electric field control. This ensures consistent light conversion across all viewing angles, eliminating color temperature variations and improving emission characteristic reliability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Manufacturing precision

If syringe or stencil method is used, then phosphor coating can be applied, but contamination from ambient air affects deposition quality

Engineering Contradiction:

Improvedeposition uniformityVSAvoidambient air contamination

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent implements a closed-loop system that seals the electrolyte solution and LED chips from ambient air during the electrophoretic deposition process. This inert environment protection prevents contamination that would otherwise affect deposition uniformity and phosphor particle suspension stability.

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

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 system achieves a uniform and repeatable deposition of phosphor materials on LEDs, improving color consistency and emission characteristics by minimizing exposure to impurities and moisture, allowing for batch processing without further handling and enabling uniform light emission across different angles.

Implementation Method 1

A voltage supply applies a voltage to the semiconductor device and the mixture to cause the material to deposit on the semiconductor device

Methodology Applied

Scientific EffectElectrophoretic deposition: Electrophoretic Deposition

Data Source

PatentUS8563339B2System for and method for closed loop electrophoretic deposition of phosphor materials on semiconductor devices

Publication Date: 2013.10.22 CREELED INC

AI summary

One close loop system and method for electrophoretic deposition (EPD) of phosphor material on light emitting diodes (LEDs). The system comprises a deposition chamber sealed from ambient air. A mixture of phosphor material and solution is provided to the chamber with the mixture also being sealed from ambient air. A carrier holds a batch of LEDs in the chamber with the mixture contacting the areas of the LEDs for phosphor deposition. A voltage supply applies a voltage to the LEDs and the mixture to cause the phosphor material to deposit on the LEDs at the mixture contacting areas.