Flip-Chip LED Transparent Bonding Layer Thickness Gradient
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Solution Overview
Problem
Conventional flip-chip light emitting devices face issues with interstices at the interface between the transparent bonding layer and the protective insulating layer, allowing liquids and metal ions to pass through, and cracks in the protective insulating layer during the cutting process, leading to detachment and failure of the protective function.
Innovation Solution
A flip-chip light emitting device with a transparent substrate, an epitaxial light-emitting structure having a roughened bottom surface, a transparent bonding layer with varying thickness sections and roughness, and a protective insulating layer disposed over the light-emitting structure, where the bonding layer's smaller-thickness section faces away from the substrate and meshes with the roughened bottom surface, reducing interstices and enhancing bonding strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a roughened interface is formed between the transparent bonding layer and the protective insulating layer to enhance light emission efficiency, then light emission efficiency is improved, but interstices are created that allow liquids and metal ions to pass through causing damage
Solution Approach 1:
The bonding layer is designed with different thicknesses at different locations: a first thickness at the first interface (with rough surface) and a second thickness at the second interface (with smooth surface). This local variation in thickness allows the rough surface to enhance light emission while the thicker region provides barrier protection against liquid and metal ion penetration.
2Illumination intensity
If a roughened interface is formed between the transparent bonding layer and the protective insulating layer, then light emission efficiency is improved, but cracks are generated in the protective insulating layer during cutting process leading to detachment
Solution Approach 1:
The bonding layer has a smooth second surface that interfaces with the protective insulating layer, unlike the rough first surface. This smooth interface prevents stress concentration and crack initiation during cutting, while the thickness variation ensures adequate bonding strength. The protective insulating layer remains intact without detachment.
3Ease of manufacture
If the bonding layer has uniform thickness, then manufacturing is simplified, but it cannot simultaneously provide adequate protection and prevent interstices formation
Solution Approach 1:
The thickness parameter of the bonding layer is varied spatially to create a thickness gradient. The bonding layer transitions from a first thickness at the rough first interface to a second thickness at the smooth second interface. This parameter change enables the structure to simultaneously achieve protection against interstices, prevent cracking, and maintain manufacturing feasibility through controlled thickness variation.
Data Source
AI summary
A flip-chip light emitting device includes a transparent substrate, an epitaxial light-emitting structure, a transparent bonding layer interposed between the transparent substrate and the light-emitting structure, and a protective insulating layer disposed over the light-emitting structure and the bonding layer. The transparent bonding layer has a smaller-thickness section that has a first contact surface for the protective insulating layer to be disposed thereover, and a larger-thickness section that has a second contact surface meshing with and bonded to a roughened bottom surface of the light-emitting structure. The first contact surface is smaller in roughness than the second contact surface. A method for producing the device is also disclosed.