Phosphor Molded Member via Spark Plasma Sintering
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Solution Overview
Problem
Conventional light emitting devices using phosphor and glass powders face issues such as low light extraction efficiency, brittleness, and poor thermal stability due to low melting point glasses and limited phosphor concentration, leading to disconnection and detachment of LED chips and poor chemical stability.
Innovation Solution
The Spark Plasma Sintering method is used to melt a mixture of phosphor and inorganic powders, achieving a high phosphor concentration of 5% or greater by weight, resulting in a dense, hard, and thin phosphor-containing molded member with high light extraction efficiency and improved thermal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If low melting point glass is used as a binder to apply phosphor around LED chip, then the phosphor can be easily applied and bonded, but the light extraction efficiency deteriorates and chemical stability becomes poor
Solution Approach 1:
The invention changes the key parameter of glass melting point from low (conventional) to high (above 500°C). This parameter change resolves the contradiction by enabling the use of high melting point glass with excellent light transmission properties and chemical stability, while still achieving easy phosphor application through the glass's inherent bonding capabilities at elevated temperatures.
Solution Approach 2:
The invention creates a composite material system consisting of high melting point glass, phosphor particles, and optional inorganic fillers. This composite structure combines the light transmission properties of glass, the light conversion properties of phosphor, and the structural stability of inorganic fillers, achieving both ease of manufacture and high light extraction efficiency.
2Power
If high concentration of phosphor powder is mixed with glass powder, then the light conversion efficiency increases, but the molded member becomes very brittle
Solution Approach 1:
The invention changes the parameter of glass powder particle size to fine particles (10 μm to 100 μm average diameter). This parameter change allows high phosphor concentration (5% or more by weight) to be incorporated while maintaining moldability and reducing brittleness, as the fine glass particles can better fill spaces and distribute stress uniformly throughout the composite structure.
Solution Approach 2:
The invention applies local quality by using fine glass particles that can adapt to local regions with high phosphor concentration. The fine particles fill the interstices between phosphor grains, creating a more homogeneous local structure that maintains mechanical integrity even at high phosphor concentrations, thereby preventing brittleness while preserving light conversion efficiency.
3Device complexity
If conventional sintering method is used to form phosphor-containing molded member, then the process is simple, but the sintering temperature must be very high and time-consuming
Solution Approach 1:
The invention replaces the conventional thermal sintering mechanism with Spark Plasma Sintering, which uses pulsed electric current and plasma discharge to achieve rapid heating and sintering. This substitution of the heating mechanism allows sintering to occur at lower temperatures and in shorter times while maintaining process simplicity, as the electric field directly energizes the particles for bonding.
Solution Approach 2:
The invention employs periodic pulsed electric current in the Spark Plasma Sintering process. The pulsed nature of the current creates periodic plasma discharges that rapidly heat and bond the particles. This periodic action achieves effective sintering at lower average temperatures and reduces overall processing time compared to continuous conventional sintering methods.
4Ease of manufacture
If low melting point glass is used, then the glass can be easily melted and formed, but the LED chip may disconnect or detach due to expansion coefficient difference
Solution Approach 1:
The invention changes the glass melting point parameter to above 500°C, which is sufficiently high to match the thermal stability requirements of LED chips. High melting point glass inherently has better thermal stability and matched thermal expansion properties, preventing chip disconnection or detachment during thermal cycling while still allowing easy forming through the glass's plasticity at elevated temperatures.
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 method allows for the production of a phosphor-containing molded member with high light extraction efficiency and thermal stability, preventing light loss and maintaining phosphor dispersion, enabling the creation of a strong and efficient light emitting device capable of emitting white light.
Implementation Method 1
The Spark Plasma Sintering method is used to melt a mixture of phosphor and inorganic powders
Implementation Method 2
The Spark Plasma Sintering method is used to melt a mixture of phosphor and inorganic powders
Implementation Method 3
a phosphor-containing molded member which is obtained by melting a mixture of a phosphor powder and an inorganic member powder by using the Spark Plasma Sintering method
Data Source
AI summary
In a method of manufacturing a phosphor-containing molded member, an inorganic powder in a mixture with a phosphor powder is melted by using Spark Plasma Sintering method, and then cooled. In a phosphor-containing molded member, a content of the phosphor therein is 5% by weight or more.