Wafer-Level LED Reflector Molding for Light Extraction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing LED packaging methods are inefficient in recycling side emissions and controlling light output at various angles, leading to reduced light extraction and increased manufacturing costs due to the use of materials like PPA resin, which experiences yellowing and adhesion issues.
Innovation Solution
The method involves bonding an LED die to a package wafer, electrically connecting it, forming a phosphor coating, molding a lens, and molding a reflector using silicone materials with high reflectivity and thermal stability, which are formed on the package wafer before or after attaching the LED die, to redirect side emissions effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PPA resin is used for molding the reflector, then the reflector can be formed with good initial reflectivity, but the reflectivity deteriorates over time due to yellowing and adhesion issues
Solution Approach 1:
The patent changes the material parameter from PPA resin to silicone-based material, which has superior thermal stability and resistance to yellowing. This material substitution maintains high reflectivity over extended periods by resisting chemical degradation and adhesion loss that plagues PPA resin in high-temperature LED operating environments
Solution Approach 2:
The patent employs a composite structure combining silicone base material with aluminum powder or other reflective particles. This composite formulation achieves both the structural integrity needed for molding and the optical properties required for sustained high reflectivity, while the silicone matrix provides thermal stability that prevents degradation
2Productivity
If side emissions are not redirected, then the packaging process is simpler, but light extraction efficiency is reduced
Solution Approach 1:
The patent merges the reflector molding operation with the existing lens molding process by using a dual-cavity mold. The same molding step that forms the lens also forms the reflector in the annular region, consolidating two potential operations into one and achieving light redirection without proportionally increasing process complexity
Solution Approach 2:
The molding process is designed to perform multiple functions simultaneously: forming the lens, forming the reflector structure, and positioning both components relative to each other in a single operation. This multi-functionality improves light extraction efficiency while minimizing the increase in manufacturing complexity
3Manufacturing precision
If the reflector is molded after bonding the LED die, then the reflector can be precisely positioned, but the manufacturing process takes longer
Solution Approach 1:
The reflector is molded in advance as part of the package substrate preparation, before the LED die is bonded. This preliminary action allows the reflector to be pre-positioned and cured, then the LED die is simply placed onto the prepared substrate, maintaining precision while enabling parallel processing that reduces overall cycle time
Solution Approach 2:
The molding operation is integrated into the substrate fabrication sequence, allowing multiple components (lens, reflector, substrate) to be formed in a coordinated manner before final assembly. This preliminary formation of components enables subsequent rapid assembly while maintaining high positioning accuracy through pre-aligned features
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 light extraction by redirecting side emissions, maintains reflectivity, and reduces manufacturing costs by using stable silicone materials that do not yellow or delaminate, thereby improving the overall light output and longevity of the LED package.
Implementation Method 1
molding a reflector on the package wafer... The molded reflector is angled to redirect LED side emissions toward a direction away from the package wafer
Implementation Method 2
forming a phosphor coating over the LED die on the package wafer... The phosphors Stokes shift blue light or other shorter wavelength light to a longer wavelength
Data Source
AI summary
An optical emitter is fabricated by bonding a Light-Emitting Diode (LED) die to a package wafer, electrically connecting the LED die and the package wafer, forming a phosphor coating over the LED die on the package wafer, molding a lens over the LED die on the package wafer, molding a reflector on the package wafer, and dicing the wafer into at least one optical emitter.