LED Phosphor Slurry Coating Uniformity via Preheating
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Solution Overview
Problem
Conventional methods for manufacturing LEDs with white light emission face challenges in achieving uniform coating thickness and color temperature, particularly with silicone-based binders, leading to poor spatial uniformity and high production costs due to low productivity and inefficiencies in coating processes.
Innovation Solution
A method involving the application of multiple thin layers of phosphor slurries with specific viscosity and binder ratios, using atomizing devices for air spraying, and a pulsed process to achieve uniform coating on LEDs, combined with controlled drying and curing to enhance productivity and quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a slurry containing phosphor and binder is applied to LED chip by spraying, then coating can be formed on the chip surface, but the coating thickness becomes non-uniform due to viscosity changes during heating and separation from chip surfaces
Solution Approach 1:
The LED chip is pre-heated to a specific temperature range (40-80°C) before slurry application. This preliminary heating prevents excessive viscosity decrease during coating, maintaining slurry stability and preventing separation from chip surfaces while ensuring uniform coating thickness.
Solution Approach 2:
The invention optimizes the heating temperature parameter to a specific range (40-80°C) that balances viscosity control and coating quality. This parameter change prevents both excessive viscosity (which would cause poor coverage) and excessive thinning (which would cause separation), resolving the contradiction between coating uniformity and viscosity stability.
2Productivity
If the LED chip is heated at high temperature to promote binder cross-linking, then productivity increases, but coating unevenness and pin holes occur due to solvent vapor bumping
Solution Approach 1:
The chip is pre-heated to a moderate temperature (40-80°C) before slurry application, and the slurry itself contains heating components that promote gradual binder cross-linking during and after coating. This staged approach prevents sudden solvent vapor bumping while maintaining productivity.
Solution Approach 2:
The coating process uses periodic heating and drying cycles rather than continuous high-temperature heating. This allows controlled solvent evaporation and gradual binder cross-linking, preventing pin holes and surface defects while maintaining efficient production.
3Ease of manufacture
If common air spraying is used to coat LED side surfaces, then coating application is simplified, but corners cannot be coated at desired thickness due to air cushion effect
Solution Approach 1:
The LED chip is pre-heated before spraying, which reduces slurry viscosity and improves particle deposition on vertical and corner surfaces. This preliminary heating enables common air spraying to achieve adequate corner coverage without complex spray techniques.
Solution Approach 2:
The invention optimizes spray parameters including air pressure, spray distance, and slurry viscosity (through solvent selection and heating) to enable effective corner coating with standard air spray equipment, maintaining process simplicity while improving corner coverage quality.
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 results in improved durability, color fastness, and spatial uniformity of LED coatings, reducing production time and costs while maintaining high-quality coatings on both the surface and side surfaces of LEDs.
Implementation Method 1
transferring the LED chip to a drying device and evaporating the solvent to form a solid layer
Implementation Method 2
setting a temperature of the heating table in a range between 40° C. to 80° C.
Implementation Method 3
using atomizing devices for air spraying
Data Source
AI summary
A method for manufacturing an LED includes preparing a plurality of different kinds of slurries with a plurality of different kinds of phosphors, a binder, and a solvent, with prescribed weight ratios and viscosities; applying at least one slurry to a substrate LED while vaporizing the solvent instantaneously to form at least one thin layer; transferring the substrate LED to a drying device and drying the substrate LED; forming laminated layers of the plurality of kinds of slurries on the substrate LED; and finally drying and curing the binder to form a dried multilayer coating composed of thin layers of the plurality of kinds of slurries.