Wafer-Level Phosphor Coating for White LED Uniformity

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Solution Overview

Problem

The existing methods for manufacturing white light-emitting devices face challenges in achieving uniform optical characteristics due to dispersion during the formation of the phosphor layer in the packaging process, leading to variability in the quality of light-emitting device packages.

Innovation Solution

The method involves forming a phosphor layer on the emission surface of semiconductor light-emitting devices at the wafer-level by disposing the thinned wafer on a carrier film, using a vacuum table with a stepped structure, and applying a phosphor paste through a printing mask, which is then hardened to ensure uniform coating and prevent warpage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the phosphor layer is formed during the packaging process by coating phosphor paste on individual light emitting devices, then the manufacturing process is flexible and easy to operate, but the optical characteristics of each completed light-emitting device package vary due to dispersion generated while forming the phosphor layer in each packaging process

Engineering Contradiction:

Improveease of forming phosphor layerVSAvoiduniformity of optical characteristics

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The phosphor layer is formed on the emission surface of the semiconductor light-emitting device before the packaging process. Specifically, the phosphor layer is formed on the wafer-level device before separation and packaging, which eliminates the dispersion issues that occur when forming phosphor layers individually during packaging. This preliminary action ensures uniform optical characteristics across all devices while maintaining manufacturing efficiency.

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If the phosphor layer is formed on the emission surface before packaging, then uniform optical characteristics are achieved, but the wafer must be thinned and handled carefully to prevent damage

Engineering Contradiction:

Improveuniformity of optical characteristicsVSAvoidrisk of wafer damage

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

A support layer is formed on the back surface of the wafer before thinning and phosphor layer formation. This support layer provides mechanical strength and prevents wafer breakage during the thinning process and subsequent handling. The support layer acts as a cushioning structure that compensates for the reduced strength of the thinned wafer, ensuring reliable processing while maintaining uniform optical characteristics.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Manufacturing precision

If the wafer is thinned to form the phosphor layer on the emission surface, then uniform coating is achieved, but the thinned wafer becomes more susceptible to warpage and breakage

Engineering Contradiction:

Improveuniformity of phosphor coatingVSAvoidwafer mechanical strength

Core Design Contradiction:

Manufacturing precisionVSStrength

Solution Approach 1:

A support layer is formed on the back surface of the wafer before thinning to provide mechanical strength during the thinning process and prevent warpage and breakage of the thinned wafer during subsequent handling and phosphor layer formation.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The wafer is thinned to a controlled thickness range (10-50 micrometers) to achieve uniform phosphor coating while maintaining sufficient mechanical strength. This parameter optimization balances the need for uniform coating with the need to prevent warpage and breakage.

Inventive Principle:

Principle #35Parameter changes

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 the production of white light-emitting devices with consistent emission characteristics by forming the phosphor layer before wafer thinning, reducing the risk of damage and ensuring uniform quality in the final light-emitting device packages.

Implementation Method 1

closely adhering and fixing the carrier film on the vacuum table by vacuum suction pressure

Methodology Applied

Scientific EffectVacuum suction pressure: Vacuum

Implementation Method 2

forming the phosphor layer by hardening the phosphor paste

Methodology Applied

Scientific EffectHardening of phosphor paste: Photopolymerisation

Data Source

PatentUS9272300B2Method and apparatus for manufacturing white light-emitting device

Publication Date: 2016.03.01 SAMSUNG ELECTRONICS CO LTD

AI summary

Methods and apparatus for manufacturing a semiconductor light-emitting device that emits white light by forming a phosphor layer on an emission surface of the semiconductor light-emitting device at a wafer-level. The method includes: forming a plurality of light-emitting devices on a wafer; thinning the wafer, on which the plurality of light-emitting devices are formed; disposing the thinned wafer on a carrier film; and forming a phosphor layer on an emission surface of the plurality of light-emitting devices on the wafer.