Centrifugal Spin Coating for Flat Phosphor Layer in LED Structure
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Solution Overview
Problem
The existing methods for forming white light LEDs using a blue light GaN LED with a phosphor layer result in an uneven phosphor layer surface, leading to light inconsistency and spots, which are problematic for applications requiring high light consistency and color rendition in LED TVs and automobile headlights.
Innovation Solution
A method involving centrifugal spin coating is used to form a phosphor layer with a flat surface above the light emitting surface of an LED wafer, which simplifies the subsequent packaging process and improves optical performance by ensuring consistent light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a phosphor layer is formed by conventional coating methods, then the sealing process is completed, but the phosphor layer surface becomes uneven causing light spots and light inconsistency
Solution Approach 1:
The patent applies a planarization layer over the phosphor layer before completing the sealing process. This preliminary action ensures that the surface is flattened in advance, preventing light spots and inconsistency issues that would otherwise require complex post-processing or lead to product defects.
Solution Approach 2:
The planarization layer acts as an intermediary element between the phosphor layer and the upper sealing structures. This intermediate layer absorbs surface irregularities and provides a flat working surface for subsequent packaging steps, eliminating the need to directly modify the phosphor layer itself.
2Ease of manufacture
If the phosphor layer surface is uneven, then the sealing can be completed, but light consistency and color rendition are compromised
Solution Approach 1:
The planarization layer is applied in advance to flatten the phosphor layer surface before the sealing process is finalized. This preliminary surface preparation ensures uniform light emission and color rendition without compromising the ease of sealing completion.
Solution Approach 2:
The planarization layer is specifically applied to the phosphor layer region where surface irregularities exist, providing localized surface correction. This targeted approach improves light consistency in the critical emission area without affecting other parts of the LED structure.
3Device complexity
If conventional sealing methods are used, then the packaging process is straightforward, but additional planarization steps are required
Solution Approach 1:
The planarization function is merged into the sealing process by applying the planarization layer as part of the overall packaging sequence. This integration allows surface flattening to occur during the normal packaging flow without requiring separate dedicated planarization equipment or complex additional steps.
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 approach results in an LED device with improved light consistency and color purity by controlling the thickness and shape of the phosphor layer, addressing issues of light spots and inconsistency, and simplifying the packaging process.
Implementation Method 1
forming a mixture of a fluorescent substance and an adhesive above a light emitting surface of the LED wafer by centrifugal spin coating
Implementation Method 2
forming a phosphor layer with a flat surface above the light emitting surface of an LED wafer, which simplifies the subsequent packaging process
Implementation Method 3
a white light LED is formed by irradiating yellow fluorescent substances by a blue light
Data Source
AI summary
A light emitting diode (LED) structure, a LED device and methods for forming the same are provided. The LED structure comprises a LED wafer; and a phosphor layer having a flat surface and formed above a light emitting surface of the LED wafer, in which the phosphor layer is formed by centrifugal spin coating.