Light-emitting Device Package Reflective Metal Layer Design
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Solution Overview
Problem
Conventional light-emitting device packages face challenges in maximizing the reflective region and reducing optical loss, particularly in Chip on Board (COB) type packages, where the presence of a solder mask around the light-emitting device chip hinders the formation of a reflective cavity and requires long metal wires for connections, affecting reliability and optical efficiency.
Innovation Solution
The proposed solution involves a light-emitting device package design with a metal layer acting as both a heat sink and reflective surface, featuring an insulating layer, electrode patterns, and electrode pads disposed to maximize reflectivity. The metal layer is coated with a transparent insulating material, and the electrode pads are arranged to minimize wire length, with shared pads for multiple light-emitting device chips to simplify manufacturing and enhance reflectivity. Additionally, a phosphor layer and optical lens can be integrated to optimize light emission properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solder mask is used around the light-emitting device chip in conventional COB packages, then electrical insulation and protection are provided, but the reflective region is hindered and optical loss increases
Solution Approach 1:
The patent removes the solder mask from the reflective region area, extracting only the necessary protective functions to specific locations (edge portions) while eliminating the mask from regions where it would interfere with light reflection. This allows the metal layer to serve as an effective reflective surface without the optical blocking effect of the solder mask.
Solution Approach 2:
The solder mask is selectively applied only to edge portions of the substrate that require electrical insulation and protection, while leaving the central reflective region exposed. This local differentiation allows each area to have the properties needed for its specific function: protection where needed and reflectivity where light emission occurs.
2Reliability
If long metal wires are used for connections in conventional COB packages, then electrode connections are achieved, but reliability decreases and manufacturing complexity increases
Solution Approach 1:
Electrode pads are pre-positioned around the light-emitting device chip before chip mounting, allowing for optimized short wire connections. The pads are strategically located to minimize wire length while ensuring proper electrical connectivity, reducing both complexity and potential failure points.
3Loss of energy
If the reflective region is maximized in COB packages, then optical efficiency improves, but the presence of solder mask and complex electrode arrangements hinder this
Solution Approach 1:
The metal layer serves multiple functions simultaneously: it acts as the reflective surface for light emission, provides the substrate structure, and serves as the electrode connection layer. This multi-functionality eliminates the need for separate reflective coating layers and simplifies the overall structure while maximizing the reflective area.
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 design effectively increases the reflective area, reduces optical loss, and enhances the brightness of the light-emitting device package by ensuring maximum light reflection from the metal layer, while simplifying the manufacturing process and improving reliability through shorter wire connections and shared electrode pads.
Implementation Method 1
a metal layer (10), an insulating layer (20) on the metal layer (10), a first electrode pattern (30) on an edge portion of the insulating layer (20), a solder mask pattern (40) on an edge portion of the insulating layer (20) and covering the first electrode pattern (30), at least one light-emitting device chip (50) on the insulating layer (20), at least one electrode pad (60) around the light-emitting device chip (50) on the insulating layer (20), and a second electrode pattern (70) on the insulating layer (20) and connecting the first electrode pattern (30) and the electrode pad (60) to each other
Data Source
Figure 1~2
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AI summary
A light-emitting device package uses a metal layer (10) as a reflective region and includes a light-emitting device chip (50) and an electrode pad (60) that are disposed on an insulating layer (20). In addition, the electrode pad and an electrode pattern of a printed circuit board (30) are connected to each other by an electrode pattern (70) formed of conductive ink. A method of manufacturing a light-emitting device package includes forming an insulating layer on a metal layer, and bonding a light-emitting device chip and an electrode pad on the insulating layer. The electrode pad and a printed circuit board are connected to each other by conductive ink.