Wavelength Converting Member Color Control via Laser Ablation

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Solution Overview

Problem

Current semiconductor light emitting devices, such as phosphor converted LEDs, face significant challenges in achieving precise color control, resulting in large variations in correlated color temperature (CCT) that are not acceptable for most applications, despite improvements over the years.

Innovation Solution

A method involving a layer of wavelength converting material is applied over a light emitting element, and the wavelength spectrum is adjusted by altering the amount of this material through laser ablation to achieve the desired CCT, ensuring consistent color output.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If phosphor converted LEDs are used to produce white light, then the devices can be manufactured with standard phosphor materials, but the correlated color temperature varies significantly (2000K to 3000K for white parts, 5500K to 8500K for CCT)

Engineering Contradiction:

ImprovemanufacturabilityVSAvoidcolor consistency

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent applies preliminary action by pre-coating the LED die with a wavelength converting material layer before packaging. This allows the color properties to be established during manufacturing rather than requiring post-production adjustment, improving both manufacturability and color consistency.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the parameter of wavelength converting material thickness to control color output. By precisely controlling the thickness of the coating layer, the patent achieves consistent color temperature and CCT across production batches, resolving the manufacturing precision issue while maintaining ease of manufacture.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If standard phosphor converted LED technology is used, then commercial availability is achieved, but color temperature variations are too large to be acceptable for most applications

Engineering Contradiction:

Improvecommercial availabilityVSAvoidcolor temperature control

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent replaces mechanical adjustment methods with a chemical/physical solution by using wavelength converting material coating thickness control. This substitution enables precise color temperature control (within 200K of target) while maintaining commercial viability through a manufacturable coating process.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Manufacturing precision

If phosphor layer thickness is adjusted to control hue, then color uniformity can be improved, but additional processing steps are required

Engineering Contradiction:

Improvecolor uniformityVSAvoidprocessing steps

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent merges the wavelength converting function directly into the LED die structure by coating the die surface. This integration eliminates the need for separate phosphor layer application and adjustment steps, achieving color uniformity without increasing device complexity.

Inventive Principle:

Principle #5Merging (Combining)

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 allows for precise control of the wavelength spectrum and correlated color temperature, reducing variations and enhancing color consistency, making the devices more suitable for various applications.

Implementation Method 1

a layer of wavelength converting material is provided over a light emitting element

Methodology Applied

Scientific EffectPhotoluminescence: Photoluminescence

Implementation Method 2

the wavelength converting material is corrected by altering the amount of wavelength converting material in the wavelength converting member to produce the desired wavelength spectrum. The wavelength converting member is corrected by reducing the amount of wavelength converting material through laser ablation

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Data Source

PatentEP2030255B1Cross control by alteration of wavelength converting member

Publication Date: 2017.03.01 PHILIPS LUMILEDS LIGHTING COMPANY LLC

AI summary

A light emitting device is produced by depositing a layer of wavelength converting material over the light emitting device, testing the device to determine the wavelength spectrum produced and correcting the wavelength converting member to produce the desired wavelength spectrum. The wavelength converting member may be corrected by reducing or increasing the amount of wavelength converting material. In one embodiment, the amount of wavelength converting material in the wavelength converting member is reduced, e.g., through laser ablation or etching, to produce the desired wavelength spectrum.