Light-Emitting Device Package Reflective Layer Stability
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Solution Overview
Problem
Existing light-emitting device packages face challenges in reliability due to issues such as migration, agglomeration, and peeling off of reflective layers, as well as diffusion of solder materials, which affect the light emission performance.
Innovation Solution
A light-emitting device package design that includes a conductive capping layer surrounding the reflective layer to increase its deposition area, prevent material diffusion, and enhance structural integrity, featuring a configuration with a transparent electrode layer, passivation layer, and a conductive capping layer made of materials like Cr, Al, Ni, or Ti, which electrically isolates the light-emitting structure and electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a reflective layer is deposited to improve light emission efficiency, then light emission efficiency is improved, but the reflective layer migrates, agglomerates, and peels off reducing reliability
Solution Approach 1:
A conductive capping layer is introduced as an intermediary between the reflective layer and the surrounding environment. This capping layer prevents direct exposure of the reflective layer to conditions that cause migration and peeling, while maintaining the reflective layer's light emission function. The capping layer acts as a protective mediator that resolves the contradiction between maintaining high reflectivity and ensuring structural stability.
Solution Approach 2:
The device structure is formed as a composite multi-layer system including the reflective layer, conductive capping layer, transparent electrode layer, and passivation layer. Each layer contributes specific properties: the reflective layer provides high reflectivity, the conductive capping layer provides protection and electrical conductivity, and the passivation layer provides electrical isolation. This composite structure resolves the contradiction by combining materials with complementary functions.
2Reliability
If the conductive capping layer is formed to surround the reflective layer, then reliability is improved by preventing material diffusion, but device complexity increases
Solution Approach 1:
The conductive capping layer performs multiple functions simultaneously: it protects the reflective layer from migration and peeling, provides electrical conductivity for electrode connection, and prevents diffusion of solder materials. By consolidating these multiple functions into a single layer, the design improves reliability without proportionally increasing complexity, as the capping layer replaces what would otherwise require multiple separate protective and conductive elements.
Solution Approach 2:
The conductive capping layer merges the protective function (preventing reflective layer degradation) with the conductive function (providing electrical connection). This consolidation eliminates the need for separate protective coatings and conductive layers, thereby improving reliability while minimizing the increase in structural complexity through functional integration.
3Power
If solder materials are used to connect electrodes, then electrical connection is achieved, but solder materials diffuse to the reflective layer affecting light emission performance
Solution Approach 1:
The conductive capping layer serves as an intermediary barrier between the solder materials and the reflective layer. It allows electrical connection to be established through the capping layer while preventing solder diffusion from reaching the reflective layer. This mediator maintains both the electrical connectivity function and the optical performance by blocking the harmful diffusion path.
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 prevents migration and peeling of the reflective layer, maintains light emission efficiency, and simplifies the manufacturing process by forming the conductive capping layer simultaneously with the first electrode, thereby improving the overall reliability and performance of the light-emitting device package.
Implementation Method 1
a reflective layer disposed so as to extend from the upper part of the transparent electrode layer to the upper part of the passivation layer in a horizontal direction
Implementation Method 2
the passivation layer may electrically isolate the side part of the light-emitting structure and the first electrode from each other
Data Source
AI summary
A light-emitting device package of an embodiment includes a light-emitting structure including first and second conductive semiconductor layers and an active layer disposed between the first and second conductive semiconductor layers; a light-transmitting electrode layer disposed on the second conductive semiconductor layer; a passivation layer disposed on the second conductive semiconductor layer and a mesa-exposed portion of the first conductive semiconductor layer; a reflection layer disposed from the top of the light-transmitting electrode layer to the top of the passivation layer in a horizontal direction perpendicular to the thickness direction of the light-emitting structure; and a conductive capping layer disposed on the reflection layer.