LED Phosphor Coating via Screen Printing Template

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Solution Overview

Problem

The existing phosphor coating methods for white light emitting diodes (WLEDs) face issues with uneven coating due to gravity and surface tension, leading to photochromic unevenness, reduced yield, and material waste, as well as potential electric leakage and light absorption from scrap irons during screen printing.

Innovation Solution

A new phosphor conformal coating method using a screen printing process with a protection layer, where the phosphor is mixed with gel and coated evenly on the LED chip, allowing for recycling of excess phosphor without pollution, ensuring even light emission and reducing material waste.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If traditional phosphor dispensing process is used, then the process is simple, but the phosphor coating is uneven due to gravity and surface tension, leading to photochromic unevenness

Engineering Contradiction:

Improvephosphor coating uniformityVSAvoidcoating process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent replaces the traditional mechanical dispensing process with a screen printing process. The screen printing template with precise openings allows phosphor gel to be deposited uniformly through mechanical pressure and squeegee action, eliminating the influence of gravity and surface tension that cause uneven coating in dispensing methods.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the physical state and delivery method of phosphor from loose particles to a gel formulation. The phosphor gel has controlled viscosity and adhesion properties that enable it to be printed uniformly through screen printing, achieving consistent coating thickness and distribution that cannot be obtained through traditional dispensing.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If screen printing is used for phosphor coating, then the phosphor layer thickness can be controlled, but scrap irons pollute the phosphor, causing electric leakage and light absorption

Engineering Contradiction:

Improvephosphor layer thickness controlVSAvoidphosphor pollution from scrap irons

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent extracts and removes scrap irons from the phosphor gel mixture before the screen printing process. By eliminating these harmful particles in advance, the phosphor gel becomes clean and suitable for precise screen printing, achieving both good thickness control and freedom from pollution-related defects.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent performs preliminary cleaning and filtration of the phosphor gel to remove scrap irons before the actual screen printing process. This preliminary action prevents contamination during coating, ensuring that the phosphor layer is free from particles that would cause electric leakage or light absorption issues.

Inventive Principle:

Principle #10Preliminary action

3Manufacturing precision

If screen printing is used for phosphor coating, then the coating evenness is improved, but the process complexity increases due to template mounting and removal

Engineering Contradiction:

Improvephosphor coating evennessVSAvoidscreen printing process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent implements a systematic process for removing and recovering the screen printing template after phosphor deposition. The template is carefully removed from the LED chip surface, and any residual phosphor is recovered and recycled. This approach maintains the coating evenness benefits of screen printing while managing the process complexity through standardized template handling procedures.

Inventive Principle:

Principle #34Discarding and recovering

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 method achieves improved light evenness, reduced material waste, and enhanced control over phosphor layer thickness, while preventing electric leakage and light absorption issues, thus increasing the luminous efficiency and yield of WLEDs.

Implementation Method 1

printing the phosphor over the chip surface via silk screen printing process

Methodology Applied

Scientific EffectScreen printing:

Implementation Method 2

baking the phosphor for curing

Methodology Applied

Scientific EffectCuring:

Data Source

PatentUS10790418B2Light emitting diode fabrication method

Publication Date: 2020.09.29 QUANZHOU SANAN SEMICON TECH CO LTD

AI summary

A fabrication method for a light emitting diode (LED), including: 1) mounting a LED chip on a substrate; 2) mounting a screen printing template on the LED chip; 3) coating a silicone gel layer over the surface of the screen printing template; 4) printing the phosphor: printing the phosphor over the chip surface via silk screen printing process and recycling the excess phosphor; and 5) removing the screen printing template and baking the phosphor for curing, and coating the cured phosphor over the chip surface. In the packaging method of the present disclosure, the unused phosphor can be recycled because it is not polluted by the screen printing template material.