LED Package Composite Reflective Layer for Moisture Protection
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Solution Overview
Problem
The development of LED packages faces challenges in maintaining uniform light output and preventing discoloration of lead frames due to moisture and oxygen exposure, which affects reflectivity and manufacturing efficiency.
Innovation Solution
The use of a second reflective layer with a refractive index of 2.0 or higher, formed of materials like TiO2 or Nb2O3, is applied over the first reflective layer to prevent moisture and oxygen permeation, and is designed to cover the lead frames and LED chip, forming a distributed Bragg reflector to enhance light extraction efficiency and prevent discoloration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a first reflective layer is applied on the lead frame to improve light extraction efficiency, then light extraction efficiency is improved, but the lead frame discoloration due to moisture and oxygen permeation occurs
Solution Approach 1:
The patent applies a composite reflective layer structure consisting of a first reflective layer (silver or aluminum) for high reflectivity and a second reflective layer (TiO2, Nb2O3, or WS2 with refractive index ≥2.0) for moisture and oxygen barrier properties. This composite structure simultaneously achieves high light extraction efficiency and prevents lead frame discoloration by combining the optical properties of metallic materials with the protective properties of high-refractive-index ceramic materials.
Solution Approach 2:
The patent specifies precise thickness parameters for the reflective layers to optimize both optical performance and protective function. The first reflective layer is controlled at 50-200 nm thickness while the second reflective layer is controlled at 10-50 nm thickness. These parameter optimizations ensure sufficient reflectivity while maintaining effective barrier properties against moisture and oxygen permeation.
2Reliability
If the second reflective layer is designed with high refractive index (≥2.0) to prevent moisture and oxygen permeation, then reliability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent defines specific thickness ranges for the reflective layers that balance protective functionality with manufacturing feasibility. The first reflective layer thickness is specified as 50-200 nm and the second reflective layer thickness as 10-50 nm. These parameter ranges are optimized to provide sufficient barrier properties while remaining within the capabilities of standard thin-film deposition processes, thereby managing manufacturing precision requirements.
3Reliability
If the reflective layers are extended to cover the entire lead frame including side surfaces, then protection against discoloration is improved, but device complexity increases
Solution Approach 1:
The patent designs the second reflective layer to extend beyond the top surface of the lead frame to cover side surfaces and potentially the entire lead frame structure. This multi-surface coverage provides comprehensive protection against moisture and oxygen permeation from all directions, ensuring uniform protection and preventing discoloration throughout the entire lead frame while maintaining a relatively simple layered deposition process.
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 solution significantly improves reflectivity and maintains surface reflectivity, reducing discoloration and enhancing external light extraction efficiency while simplifying the manufacturing process by preventing moisture and oxygen exposure.
Implementation Method 1
a second reflective layer disposed on the first reflective layer... prevent moisture and oxygen permeation
Implementation Method 2
The first refractive layer and the second refractive layer may form a distributed Bragg reflector (DBR)
Implementation Method 3
an LED chip mounted on the package body and electrically connected to the lead frames through wire bonding
Data Source
AI summary
A light emitting diode (LED) package may include a package body provided with a pair of lead frames, and an LED chip mounted on the package body and electrically connected to the lead frames through wire bonding. Each lead frame may include a first reflective layer disposed on a mounting surface on which the LED chip is disposed and a second reflective layer disposed on the first reflective layer. A wire may penetrate through the second reflective layer to be connected to the first reflective layer. Accordingly, the LED package may provide the uniform amount of light by suppressing discoloration of the lead frames, and the manufacturing time of the LED package may be reduced, leading to a reduction in manufacturing costs.