LED Die Phosphor Deposition via Dry Film Photoresist Masking
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Solution Overview
Problem
Conventional methods for depositing phosphor-containing material on LED dies for consistent light color production in mass-produced LED emitters face challenges such as excessive phosphor usage, poor cooling, and non-uniform angular distribution of light color, making it difficult to achieve reliable packaging and consistent color temperature.
Innovation Solution
A method involving a template with openings to precisely place a controlled amount of phosphor-containing material on the top surface of LED dies, using a patterned dry photoresist to mask areas and control thickness, and applying the material with a suitable viscosity to prevent settling, allowing for efficient heat dissipation and improved cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional methods use a large amount of phosphor in the cup structure, then the phosphor can be easily applied, but the cooling of phosphor and silicone material becomes poor
Solution Approach 1:
The invention divides the phosphor application area into two distinct zones: a first area on the LED die top surface for phosphor deposition, and a second area (sidewalls and bottom) free of phosphor. This segmentation allows phosphor to be applied only where needed for light conversion while maintaining thermal pathways for effective cooling in the phosphor-free zones.
Solution Approach 2:
The invention applies phosphor locally only to the first area of the LED die top surface, rather than uniformly across the entire die. This local quality approach ensures phosphor is present only where light conversion is required, while other areas maintain optimal thermal properties for cooling.
2Ease of manufacture
If conventional methods place phosphor in the cup structure, then the application process is simple, but the angular distribution of light color becomes non-uniform
Solution Approach 1:
The invention segments the die surface into a flat first area for phosphor deposition and excluded second areas, creating a controlled geometry that ensures uniform light color distribution from all viewing angles while maintaining a simple application process.
Solution Approach 2:
The invention transitions from three-dimensional phosphor filling in a cup structure to a two-dimensional planar deposition on the die top surface. This dimensional change eliminates angular dependency of light color while simplifying the application process.
3Ease of manufacture
If conventional methods use syringe to place liquid droplets of phosphor material, then the material can be applied, but the liquid mixture settles and causes color shifting
Solution Approach 1:
The invention changes the physical state parameter of the phosphor material from liquid droplets to a paste or semi-solid form with higher viscosity. This parameter change prevents settling and maintains composition stability while still allowing easy application to the die surface.
Solution Approach 2:
The invention uses a disposable stencil or mask that is discarded after single use, eliminating the need for complex reusable positioning systems and ensuring consistent phosphor placement without settlement issues.
4Illumination intensity
If conventional methods use more phosphor material, then the light output can be increased, but the packaging reliability decreases
Solution Approach 1:
The invention segments the phosphor distribution to concentrate material only in the first area on the die top surface, reducing total phosphor quantity while maintaining light output. This segmentation also improves packaging reliability by eliminating phosphor from areas where it would compromise structural integrity.
Solution Approach 2:
The invention extracts phosphor from the cup structure and surrounding areas, retaining it only on the die top surface. This extraction reduces overall phosphor usage and eliminates reliability issues associated with phosphor in the packaging structure, while maintaining sufficient light output through optimized placement.
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 phosphor usage, enhances cooling, and ensures consistent light color distribution, leading to more reliable packaging and cost-effective mass production of white LEDs with stable color temperature.
Implementation Method 1
A patterned dry photoresist film is disposed over the template and the plurality of LED dies. The dry photoresist film has a plurality of openings configured to expose a top surface of each of the LED dies
Implementation Method 2
Heat generated in the phosphor material can be dissipated through the LED die, and better cooling can reduce the temperature of the phosphor and the silicone material
Data Source
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AI summary
A method for depositing a layer of phosphor-containing material on a plurality of LED dies includes disposing a template with a plurality of openings on an adhesive tape and disposing each of a plurality of LED dies in one of the plurality of openings of the template. The method also includes forming a patterned dry film photoresist layer over the template and the plurality of LED dies. The photoresist layer has a plurality of openings configured to expose a top surface of each of the LED dies. Next, a phosphor-containing material is disposed on the exposed top surface of each the LED dies. The method further includes removing the photoresist layer and the template.