LED Substrate Silver Reflective Layer Migration Prevention
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Solution Overview
Problem
Reflective substrates used in LED products face reliability issues due to silver layer migration and corrosion, leading to degradation of reflectivity and light output, especially under temperature and blue light exposure.
Innovation Solution
A thin film stack structure is developed for LED substrates, including an anodic layer, adhesion layer, barrier layer, and dielectric layers to protect the silver reflective layer, reducing migration and corrosion, and maintaining reflectivity over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a PVD silver layer is used for high reflectivity, then reflectivity is improved, but reliability deteriorates due to silver migration and corrosion
Solution Approach 1:
The patent applies composite materials by creating a multi-layer structure consisting of a PVD silver reflective layer combined with protective dielectric layers (such as silicon oxide, silicon nitride, or silicon oxynitride) and adhesion layers (such as chromium, nickel, or titanium). This composite structure maintains the high reflectivity of the silver layer while the protective layers prevent silver migration and corrosion, and the adhesion layers ensure stable bonding between layers, thereby resolving the contradiction between reflectivity and reliability.
Solution Approach 2:
The patent uses intermediary layers to resolve the contradiction. Adhesion layers (chromium, nickel, or titanium) are introduced between the substrate and the silver reflective layer to prevent direct contact and migration. Dielectric protective layers (silicon oxide, silicon nitride, or silicon oxynitride) are introduced as intermediaries between the silver layer and the external environment to prevent sulfur attack and corrosion. These intermediary layers maintain reflectivity while preventing degradation mechanisms.
2Illumination intensity
If the silver layer is made thicker to maintain reflectivity, then reflectivity is improved, but manufacturing complexity increases
Solution Approach 1:
The patent optimizes the thickness parameter of the silver layer to a specific range (50-200 nanometers) to achieve high reflectivity without excessive thickness. This parameter optimization, combined with the introduction of protective and adhesion layers, allows the system to maintain reflectivity while avoiding the need for excessively thick silver layers that would increase manufacturing complexity and material cost.
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
The solution effectively prevents silver migration and corrosion, ensuring stable reflectivity and light output performance of LED products even under operating conditions that typically cause degradation.
Implementation Method 1
an anodic layer disposed over the substrate
Implementation Method 2
an adhesion layer disposed over the anodic layer
Implementation Method 3
a barrier layer disposed over the anodic layer
Implementation Method 4
a reflective layer disposed over the adhesion layer and the barrier layer
Implementation Method 5
a first dielectric layer disposed over the reflective layer, and a second dielectric layer disposed over the first dielectric layer
Data Source
AI summary
Aspects include features for improving the reliability of a reflective base structure for light emitting diodes (LED) chip-on-board (COB) array products. The reflective base structure reduces reflective material of a reflective layer (e.g., silver) from migrating into adjacent layers. In one configuration used to reduce the migration of reflective material, a reflective base for a light-emitting diode (LED) may comprise a substrate, a reflective layer, and a diffusion barrier layer between the substrate and the reflective layer. In another configuration used to reduce the migration of reflective material, a reflective base for an LED comprising: a substrate, a reflective layer; and a planarizing layer between the substrate and the reflective layer, a thickness of the planarizing layer between the substrate and the reflective layer being less than 70 nm.