Slim LED Chip with Bump Electrodes for Flexible Substrate Mounting
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Solution Overview
Problem
Conventional light emitting diodes (LEDs) face challenges in design flexibility due to their rigid structure, which limits their ability to be deformed and mounted on flexible substrates without tilting or experiencing reliability issues, such as disconnection and reduced durability.
Innovation Solution
A compact flip-chip type light emitting diode chip with a minimized area and thickness, featuring a substrate with protrusions, a light emitting structure with a distributed Bragg reflector, and pad electrodes, is developed to prevent tilting and ensure high production yield and durability, allowing for secure mounting on flexible substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional light emitting diodes are mounted on flexible substrates, then design freedom is improved, but tilting occurs due to solder flowability causing reliability deterioration
Solution Approach 1:
The patent inverts the conventional mounting approach by using a bump electrode structure that protrudes from the substrate surface, rather than relying on flat solder joints. This inversion allows the LED to be mounted in a flipped orientation with the bump electrode providing mechanical support that prevents tilting, while still enabling flexibility substrate mounting
Solution Approach 2:
The patent applies preliminary action by forming protrusions on the substrate surface before mounting the LED. These pre-formed protrusions serve as mechanical stops and alignment features that prevent tilting during and after the soldering process, addressing the reliability issue before it occurs
2Area of moving object
If small light emitting diodes are arranged at narrow intervals, then area is reduced, but grooves formed on leads cause disconnection upon deformation
Solution Approach 1:
The patent extracts the groove formation requirement from the lead structure by using a bump electrode mounting approach. Instead of forming grooves in the leads to prevent tilting, the invention uses the protruding bump electrode itself to provide mechanical stability, eliminating the need for groove formations that would compromise flexibility and reliability
Solution Approach 2:
The patent employs flexible substrate design with thin film structures that can deform without causing disconnection. The bump electrode structure combined with flexible substrate allows the assembly to accommodate deformation while maintaining electrical connections, unlike rigid groove structures
3Reliability
If light emitting diodes are mounted using solder, then electrical connection is achieved, but tilting occurs due to solder flowability
Solution Approach 1:
The patent inverts the conventional flat mounting interface by using a protruding bump electrode structure. This three-dimensional interface provides mechanical interlocking and prevents tilting, while still achieving reliable electrical connection through the bump electrode and solder combination
Solution Approach 2:
The patent applies preliminary action by pre-forming the bump electrode structure on the substrate before soldering. This pre-formed structure provides mechanical support and positioning that prevents tilting during the soldering process and ensures stable electrical connection
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 provides a slim, reliable, and durable light emitting diode chip that can be effectively mounted on flexible substrates, preventing tilting and ensuring high production yields while maintaining excellent electrical characteristics and luminous efficacy.
Implementation Method 1
a light reflective insulation layer covering a side surface and an upper surface of the light emitting structure, and including a first opening exposing the first conductive type semiconductor layer exposed through the hole and a second opening partially exposing the contact electrode, the light reflective insulation layer including a distributed Bragg reflector (DBR)
Data Source
AI summary
A light emitting diode chip includes: a first conductive type semiconductor layer disposed on a substrate; a mesa disposed on the first conductive type semiconductor layer and including an active layer and a second conductive type semiconductor layer; at least one groove disposed on a side surface of the mesa forming a concave region; an extension electrode forming ohmic contact with the first conductive type semiconductor layer in the concave region; an insulation layer covering the extension electrode, the first conductive type semiconductor layer, and the mesa, and including at least one first opening exposing the extension electrode and a second opening; a first pad electrode disposed on the insulation layer and electrically connected to the first conductive type semiconductor layer through the first opening; and a second pad electrode disposed on the insulation layer and electrically connected to the second conductive type semiconductor layer through the second opening.