Chip-Scale LED Reflective Structure Against Solder Diffusion
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Solution Overview
Problem
Chip-scale package type light emitting diodes face issues with solder diffusion contaminating the ohmic reflection layer, leading to reliability concerns and a lack of resistance to electrical overstress or electrostatic discharge.
Innovation Solution
A light emitting diode design incorporating a reflective structure with a conductive oxide layer, dielectric layer, and metal reflection layer replaces the conventional ohmic reflection layer, preventing solder diffusion and enhancing resistance to electrical overstress and electrostatic discharge through controlled opening sizes and shapes in the dielectric layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a flip-chip shape electrode structure with ohmic reflection layer is used, then luminous efficiency and heat dissipation characteristics are improved, but solder diffusion contaminates the ohmic reflection layer causing reliability issues
Solution Approach 1:
The device is divided into separate functional regions: a light emitting region with the mesa and semiconductor layers, and a pad region with bonding pads for electrical connection. The insulating layer creates physical separation between these regions, preventing solder from the bonding pads from diffusing into the light emitting region and contaminating the ohmic reflection layer.
Solution Approach 2:
An insulating layer is introduced as an intermediary barrier between the bonding pads and the light emitting region. This insulating layer selectively blocks solder diffusion while allowing electrical connections to be established through openings in the insulating layer, thus protecting the ohmic reflection layer from contamination.
2Reliability
If separate protection devices against electrical overstress or electrostatic discharge are added, then resistance to electrical overstress or electrostatic discharge is improved, but device complexity increases
Solution Approach 1:
The bonding pads are designed to serve multiple functions: providing electrical connections for normal operation and simultaneously acting as protection devices against electrical overstress and electrostatic discharge. The insulating layer structure enables this multi-functionality by controlling the electrical connection paths while preventing harmful solder diffusion.
Solution Approach 2:
The protection function against electrical overstress and electrostatic discharge is merged into the existing bonding pad structure. Instead of adding separate protection devices, the insulating layer configuration itself provides the protection mechanism, combining multiple functions into a single integrated structure.
3Ease of manufacture
If chip-scale package type design is used, then manufacturing process is simplified and time and cost are saved, but solder diffusion contamination occurs
Solution Approach 1:
The insulating layer serves as a mediator that enables chip-scale package manufacturing without solder diffusion contamination. It allows the simplified chip-scale bonding process to proceed while preventing solder from diffusing into the light emitting region, thus maintaining manufacturing simplicity while eliminating the harmful effect.
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 improves the reliability of the light emitting diode by preventing solder diffusion, achieving high light output, low forward voltage, and increased resistance to electrical overstress and electrostatic discharge.
Implementation Method 1
a metal reflection layer, a lower insulating layer, a first pad metal layer, a second pad metal layer, and an upper insulation layer. The metal reflection layer is disposed on the dielectric layer, and connecting to the conductive oxide layer through the openings of the dielectric layer
Data Source
AI summary
A chip-scale package type light emitting diode includes a first conductivity type semiconductor layer, a mesa, a second conductivity type semiconductor layer, a transparent conductive oxide layer, a dielectric layer, a lower insulation layer, a first pad metal layer, and a second pad metal layer, an upper insulation layer. The upper insulation layer covers the first pad metal layer and the second pad metal layer, and includes a first opening exposing the first pad metal layer and a second opening exposing the second pad metal layer. The openings of the dielectric layer include openings that have different sizes from one another.