Stencil Printing Phosphor on LED Dies for Thermal Management
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Solution Overview
Problem
Conventional methods for depositing phosphor-containing material on LED dies face challenges in achieving consistent light color temperature in mass-produced white LEDs due to excessive phosphor usage, poor cooling, and non-uniform angular distribution of light color, leading to unreliable packaging.
Innovation Solution
A method involving a template and stencil is used to precisely apply a controlled amount of phosphor-containing material directly onto the top surface of LED dies, allowing for better heat dissipation and reduced phosphor usage, with the stencil and template guiding the application to ensure uniformity and prevent excess material from settling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional methods use a large amount of phosphor-containing material in the cup structure, then the LED die can be packaged, but the phosphor usage is excessive and causes poor cooling
Solution Approach 1:
The patent applies local quality by precisely controlling the phosphor-containing material to be deposited only on the top surface of the LED die within the cup structure, rather than filling the entire cup. The stencil mask defines specific deposition areas, ensuring phosphor is placed only where needed for light conversion, reducing overall phosphor quantity while maintaining packaging reliability
Solution Approach 2:
The patent uses partial action by applying phosphor-containing material in controlled amounts through stencil printing, rather than excessive filling of the cup structure. The deposition process applies material partially - only to the top surface of the die - which reduces total phosphor usage while still achieving the necessary light conversion function and reliable packaging
2Reliability
If conventional methods use a large amount of phosphor-containing material, then the LED die can be packaged, but the heat generated in the phosphor material cannot be dissipated effectively
Solution Approach 1:
By limiting phosphor deposition to only the top surface of the LED die through stencil masking, the patent reduces the volume of phosphor material that generates heat. This localized deposition improves heat dissipation pathways while maintaining the necessary light conversion function, thereby improving packaging reliability
Solution Approach 2:
The partial deposition of phosphor-containing material - applied only where needed on the die top surface rather than filling the entire cup - reduces the total heat-generating material volume. This partial action approach allows better thermal management while still achieving reliable packaging
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 tends to settle and can lead to color shifting
Solution Approach 1:
The patent applies preliminary action by using a stencil mask before deposition to define the exact areas where phosphor-containing material should be placed. This pre-established template guides the deposition process, ensuring uniform distribution and preventing settling-induced color shifting by controlling material placement from the outset
Solution Approach 2:
The patent replaces the manual syringe-based liquid droplet application with a stencil printing process. This mechanical substitution provides better control over material distribution, preventing the settling issues that occur with syringe application while maintaining ease of manufacture through a more controllable deposition mechanism
4Reliability
If conventional methods place phosphor in the cup structure, then the LED die can be packaged, but the angular distribution of light color becomes non-uniform
Solution Approach 1:
The patent applies local quality by using a stencil mask to define precise deposition patterns on the top surface of the LED die. This ensures phosphor-containing material is placed in specific locations that optimize light extraction and angular distribution, while still maintaining the cup structure for reliable packaging
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 enables cost-effective mass production of LEDs with improved cooling and more reliable packaging, maintaining consistent light color temperature and reducing color shifting issues.
Implementation Method 1
For colored light, an LED chip is often combined with a wavelength-converting material to obtain desired output light color. For example, yellow phosphors are often combined with blue LEDs to produce white light.
Implementation Method 2
LEDs are a promising technology and are already widely deployed for specific purposes, such as traffic signals and flashlights.
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 disposing a stencil over the template and the plurality of LED dies. The stencil 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 stencil and the template.