Wavelength Conversion Layer Thickness Control in LED Manufacturing
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Solution Overview
Problem
Existing methods for manufacturing white light emitting diodes (LEDs) face challenges in achieving uniform wavelength conversion layers, leading to uneven light color distribution due to alignment issues and the need for precise positioning and electrical conductivity, which restricts material choices and applicability to various elements.
Innovation Solution
A light emitting device with a semiconductor light emitting element and a supporting body, where a wavelength conversion layer made of resin containing phosphor is continuously applied to the upper surface and side surfaces, with a thinner lower portion on the side surfaces to reduce unevenness in light color distribution, using a method that involves forming a supporting body and spraying a slurry of phosphor particles and thermosetting resin to achieve uniform thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If screen printing method is used to apply wavelength conversion layer, then manufacturing process can be implemented, but alignment precision between LED chips and stencil mask is difficult to maintain, resulting in uneven wavelength conversion layer thickness
Solution Approach 1:
A supporting body is introduced as an intermediary component between the LED chip and the wavelength conversion layer. The supporting body provides a stable platform that facilitates uniform application of the wavelength conversion layer without requiring precise alignment between the LED chip and stencil mask, thereby resolving the contradiction between ease of manufacture and manufacturing precision.
Solution Approach 2:
The invention changes the application parameters by using a slurry with specific viscosity characteristics and applying it through a spray device rather than screen printing. This parameter change enables uniform coating thickness without the alignment issues inherent in screen printing methods.
2Manufacturing precision
If electrophoresis method is used to attach phosphor particles, then uniform wavelength conversion layer can be formed, but the LED chip must be soaked in organic solvent for long time, restricting material choices
Solution Approach 1:
The invention replaces the electrophoresis method (which requires electrical conductivity and prolonged solvent soaking) with a spray coating method. This substitution eliminates the need for electrical conductivity treatment and reduces solvent exposure time, thereby maintaining wavelength conversion layer uniformity while expanding material compatibility.
3Area of stationary object
If wavelength conversion layer is applied to cover entire surface including lower portion of side surfaces, then complete coverage is achieved, but excessive thickness at lower portion causes light color unevenness
Solution Approach 1:
The invention applies the local quality principle by making the wavelength conversion layer thickness position-dependent. The layer is made thinner at the lower portion of the side surfaces and thicker at the upper portion, optimizing light extraction and color uniformity. This local variation in thickness resolves the contradiction between complete coverage and light color distribution uniformity.
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 solution ensures a uniform wavelength conversion layer on the light emitting device, reducing light color unevenness and simplifying the singulation process, while allowing for a broader range of materials and element types to be used, improving manufacturing efficiency and product consistency.
Implementation Method 1
a wavelength conversion layer is formed by spraying a slurry containing phosphor particles and a thermosetting resin with a spray device
Implementation Method 2
the thermosetting resin is cured by heating or UV irradiation
Data Source
AI summary
A method of manufacturing a light emitting device including: forming a supporting body on a mounting surface of each of semiconductor light emitting elements; arranging the semiconductor light emitting elements to be spaced apart from each other by a predetermined distance; and forming a wavelength conversion layer to continuously cover an upper surface and side surfaces of at least one of the semiconductor light emitting elements. The forming the wavelength conversion layer includes spraying a slurry provided by mixing particles of a wavelength conversion member and a thermosetting resin in a solvent onto the upper surface and the side surfaces of the semiconductor light emitting element, so that a thickness of the wavelength conversion layer at a lower portion of the side surfaces of the supporting body is smaller than the thickness on the upper surface and the side surfaces of the semiconductor light emitting element.