Phosphor-Coated LED Dies Wafer-Level Fabrication
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Solution Overview
Problem
Conventional methods for applying photoconversion materials to LEDs are inefficient and costly, leading to waste of carrier substrates during the dicing process, as they do not allow for effective application at the die level, resulting in low throughput and substrate wastage.
Innovation Solution
A method of applying a photoconversion material to LEDs at the die level, where a phosphor film is coated collectively over the LEDs before dicing, allowing for efficient use of substrates and reducing waste by reusing them, and shaping the phosphor film to function as a lens for improved light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional methods of applying photoconversion materials to LEDs are used, then the process is simple to implement, but the throughput is low and substrate wastage is high
Solution Approach 1:
The phosphor coating is applied to the LED dies before the dicing process. This preliminary action allows the entire wafer to be coated uniformly, and after dicing, each individual die retains its phosphor coating without requiring separate coating steps for each die, thereby eliminating substrate wastage and improving throughput
Solution Approach 2:
The patent combines the phosphor coating step with the wafer-level processing by coating multiple LED dies simultaneously on a single carrier substrate before dicing. This merging of operations allows efficient use of the substrate and eliminates the need to discard it after use
2Ease of manufacture
If conventional LED packaging processes using carrier substrates are used, then support is provided during fabrication, but the carrier substrate is wasted during dicing
Solution Approach 1:
The patent extracts the phosphor coating process from the individual die level and performs it at the wafer level before dicing. This allows the carrier substrate to be used purely as a temporary support during fabrication and coating, and after dicing, the substrate can be removed and reused, eliminating waste while maintaining fabrication support benefits
3Manufacturing precision
If phosphor coating is applied at the die level after dicing, then precise coating is achieved, but throughput is reduced and cost increases
Solution Approach 1:
The phosphor coating is applied preliminarily to the entire wafer before dicing into individual dies. This preliminary coating ensures uniform coverage across all dies, and the coating precision is maintained because the wafer-level coating process uses standardized techniques that ensure consistent application across the entire surface
Solution Approach 2:
The patent makes the coating process universal by applying it to the entire wafer at once rather than to individual dies. This multi-functional approach serves all LED dies simultaneously, improving throughput while maintaining precision through standardized wafer-level coating equipment and processes
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 enhances throughput, reduces substrate wastage, and improves photoconversion efficiency by applying the phosphor coating at the die level, allowing for more efficient LED packaging processes and cost-effective production.
Implementation Method 1
a photoconversion material such as phosphor may be utilized to change the light output from one color to another
Data Source
AI summary
A lighting apparatus includes a first doped semiconductor layer, a light-emitting layer disposed over the first doped semiconductor layer, a second doped semiconductor layer disposed over the light-emitting layer, a first conductive terminal, a second conductive terminal, and a photo-conversion layer. The second doped semiconductor layer has a different type of conductivity than the first doped semiconductor layer. The first conductive terminal and the second conductive terminal each are disposed below the first doped semiconductor layer. The photo-conversion layer is disposed over the second doped semiconductor layer and on side surfaces of the first and second doped semiconductor layers and the light-emitting layer. A bottommost surface of the photo-conversion layer is located closer to the second doped semiconductor layer than bottom surfaces of the first and second conductive terminals.