LED Assembly Bump Structure for Flip Bonding Reliability
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Solution Overview
Problem
Conventional LED assemblies, particularly ultraviolet LED assemblies, face challenges in reliability due to light absorption by the P-type semiconductor layer and heat generation, which affect their lifespan and performance during flip bonding processes.
Innovation Solution
The proposed LED assembly features bumps with a gold (Au) compound including tin (Sn) for one region and gold for another, along with a nickel diffusion barrier layer, to enhance electrical and thermal connectivity, and a method involving thermo-compression bonding to stabilize the flip bonding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If flip bonding is used to mount LED chip directly on carrier substrate, then miniaturization and cost reduction are achieved, but reliability and lifespan of LED assembly deteriorate
Solution Approach 1:
The bump structure is segmented into multiple functional layers: a first bump layer (Au-Sn alloy) for bonding to the LED chip, a second bump layer (pure Au) for bonding to the carrier substrate, and an optional diffusion barrier layer (Ni) in between. This segmentation allows each layer to perform its specific function optimally, resolving the contradiction between miniaturization and reliability.
Solution Approach 2:
The invention uses composite material structures for the bumps, combining Au-Sn alloy with pure Au and potentially Ni diffusion barrier. The Au-Sn alloy provides low melting point for easy bonding, while the pure Au layer provides excellent electrical conductivity and corrosion resistance, creating a composite structure that achieves both miniaturization and enhanced reliability.
2Illumination intensity
If P-type semiconductor layer is used in ultraviolet LED, then light emission is achieved, but light absorption and heat generation increase
Solution Approach 1:
The invention introduces intermediary structures (specific bump layers with particular material compositions) between the P-type semiconductor layer and the carrier substrate. These intermediary bumps with optimized thermal conductivity and bonding characteristics help transfer heat away from the light-emitting region, reducing the harmful heat generation effect while preserving light emission.
3Ease of manufacture
If conventional bump structure is used for flip bonding, then manufacturing simplicity is maintained, but bonding reliability and stability deteriorate
Solution Approach 1:
The invention changes the material parameters of the bump structure by using Au-Sn alloy instead of conventional pure Au or other materials. This parameter change (compositional change) provides lower melting point for easier bonding process while maintaining or improving bonding reliability and stability, thus resolving the contradiction between manufacturing simplicity and bonding reliability.
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 configuration improves the reliability and stability of the LED assembly by maintaining the structural integrity and thermal conductivity, leading to enhanced performance and extended lifespan, especially for ultraviolet LEDs.
Implementation Method 1
a third region between the first region and the second region, and the third region is a diffusion barrier layer
Implementation Method 2
improves the reliability and stability of the LED assembly by maintaining the structural integrity and thermal conductivity
Implementation Method 3
bumps provided on the LED and electrically connected to the semiconductor layers
Data Source
AI summary
The present invention is directed to a light emitting diode (LED) assembly and a method for fabricating the same. According to the present invention, there is provided an LED assembly comprising an LED comprising at least an N-type semiconductor layer and a P-type semiconductor layer; and bumps provided on the LED and electrically connected to the semiconductor layers, wherein the bump comprises a first region made of a gold (Au) compound including tin (Sn) and a second region made of gold.