LED Chip Fluorescent Layer Thickness for Chromaticity Control
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Solution Overview
Problem
The challenge in semiconductor light emitting devices is to minimize chromaticity variation in white light emitting diodes (LEDs) during wafer-level packaging, particularly due to emission wavelength variations among chips, which affects the color consistency of the emitted light.
Innovation Solution
A semiconductor light emitting device design featuring multiple chips with a central chip and peripheral chips, where the fluorescent body layers on the peripheral chips have the same thickness, while the central chip has a different thickness, allowing for adjustable chromaticity by varying the thickness of the fluorescent body layers and adjusting the input power to each chip, thereby achieving uniform color mixing and light distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wafer-level packaging is used to form interconnect layer, protection resin, and luminescent layer collectively for multiple chips, then manufacturing efficiency is improved, but emission wavelength variation among chips causes chromaticity variation
Solution Approach 1:
The patent applies local quality by differentiating the fluorescent body layer configuration between the central chip and peripheral chips. Specifically, the central chip has a first fluorescent body layer with a first thickness, while peripheral chips have second fluorescent body layers with a second thickness different from the first. This local differentiation allows each chip region to contribute differently to the overall chromaticity, compensating for wavelength variations and achieving uniform color mixing across all chips processed in the wafer-level packaging process.
2Adaptability or versatility
If fluorescent body layer thickness is varied among chips, then chromaticity adjustment is improved, but device structure complexity increases
Solution Approach 1:
The patent employs asymmetry by creating an intentional structural difference between the central chip and peripheral chips. The central chip features a first fluorescent body layer with a specific thickness optimized for its position, while peripheral chips have second fluorescent body layers with different thicknesses optimized for their respective positions. This asymmetric design enables precise chromaticity control across the device without requiring complex additional components or processing 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
This design effectively reduces chromaticity variation and enhances color consistency by allowing for precise adjustment of the light emission intensity and color mixing, resulting in a stable and uniform light output.
Implementation Method 1
fluorescent body layers of a same kind provided on the first faces of the chips
Data Source
AI summary
According to one embodiment, a semiconductor light emitting device includes not less than three chips. Each of the chips includes a semiconductor layer having a first face, a second face formed on a side opposite to the first face, and a light emitting layer, a p-side electrode, and an n-side electrode. The chips include a central chip centrally positioned in a plan view, and at least two peripheral chips arranged symmetrically to each other sandwiching the central chip in the plan view. A thickness of the fluorescent body layer on the first face is same among the peripheral chips, and the fluorescent body layer on the first face of the central chip and the fluorescent body layers on the first faces of the peripheral chips have thicknesses different from each other.