Wavelength Conversion Layer Manufacturing for White LEDs
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Solution Overview
Problem
Existing methods for manufacturing white LEDs with wavelength conversion layers face challenges such as uneven light color distribution due to inaccurate alignment and thickness issues in the wavelength conversion layer, and difficulties in forming uniform layers on single LED chips.
Innovation Solution
A method involving arranging semiconductor light emitting elements on an expandable sheet with an adhesive surface, forming a resin layer containing a wavelength conversion member, and expanding the sheet to singulate the elements, ensuring a stable dimensional precision and sufficient inorganic material content for effective wavelength conversion and bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wavelength conversion layer is formed by conventional methods (screen printing, spray, electrodeposition), then manufacturing process can be implemented, but alignment accuracy deteriorates and light color distribution becomes uneven
Solution Approach 1:
A release sheet is introduced as an intermediary carrier substrate. The wavelength conversion layer is formed on the release sheet first, then transferred to the LED chip. This intermediary approach enables precise alignment through positioning holes and protrusions while maintaining ease of manufacture by using simple coating methods on the release sheet.
Solution Approach 2:
The manufacturing process is segmented into distinct stages: forming the wavelength conversion layer on the release sheet, curing it, and then transferring it to the LED chip. This segmentation allows each stage to be optimized independently, improving overall precision without increasing overall complexity.
2Manufacturing precision
If wavelength conversion layer is formed on single LED chip directly, then manufacturing process is simplified, but forming uniform layer becomes difficult
Solution Approach 1:
The problem is solved by changing the dimension of the manufacturing approach. Instead of forming the layer directly on the small LED chip surface, the layer is formed on a larger release sheet first, allowing uniform coating across a larger area, then transferred to the chip. This dimensional change enables uniform layer formation that would be difficult on the small chip surface alone.
3Reliability
If inorganic material content in wavelength conversion layer is increased for sufficient phosphor content, then wavelength conversion efficiency improves, but bonding strength between inorganic materials deteriorates
Solution Approach 1:
The resin composition parameters are optimized to maintain appropriate viscosity and bonding properties even with high inorganic material content (30-99 mass%). By adjusting resin type, viscosity, and composition ratios, the patent achieves both sufficient phosphor content for wavelength conversion and adequate bonding strength to hold the inorganic materials together.
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 reduces uneven light color distribution and allows for the formation of a wavelength conversion layer with sufficient phosphor content and bonding strength, improving the manufacturing efficiency and light emission characteristics of white LEDs.
Implementation Method 1
a wavelength conversion layer which includes a resin layer containing a wavelength conversion member for converting a wavelength of light emitted from the semiconductor light emitting element
Implementation Method 2
arranging at least two of the semiconductor light emitting elements spaced apart from each other on an expandable sheet having an adhesive surface
Data Source
AI summary
A light emitting device includes at least one semiconductor light emitting element, and a wavelength conversion layer which is formed on a surface of the semiconductor light emitting element and which includes a resin layer containing a wavelength conversion member for converting a wavelength of light emitted from the semiconductor light emitting element. The wavelength conversion layer covers an upper surface or the upper surface and a side surface of the semiconductor light emitting element. A content of an inorganic material including the wavelength conversion member, or a content of an inorganic material including the wavelength conversion member and an inorganic filler, in the resin layer is 30% by mass or more and 99% by mass or less.