Die-bonded LED with Intermetallic Layers for Thermal Stress Reduction
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Solution Overview
Problem
Existing LED die-bonding methods face issues with non-uniform glue distribution, low heat resistance, and poor heat dissipation, leading to reduced luminous efficiency and reliability due to thermal stress and softening of bonding materials at elevated temperatures.
Innovation Solution
A die-bonding method involving a first and second metal thin film layer, intermetallic layers, and a die-bonding material layer with a melting point below 100°C, where the LED chip is pre-cured at a liquid-solid reaction temperature and then cured at a solid-solid reaction temperature, forming intermetallic layers with high melting points to ensure stable bonding and heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If high molecular conductive glue materials are used for die-bonding, then ease of manufacture is improved, but heat resistance and heat dissipation deteriorate
Solution Approach 1:
The patent changes the material parameter from high molecular conductive glue to eutectic bonding material, which fundamentally alters the thermal properties. The eutectic material provides high heat resistance and improved heat dissipation while maintaining manufacturability through a standardized bonding process.
Solution Approach 2:
The patent employs a composite bonding structure consisting of eutectic bonding material combined with metal materials. This composite approach achieves both high heat resistance and good heat dissipation properties, resolving the contradiction between ease of manufacture and thermal performance.
2Temperature
If eutectic bonding material with high melting point is used, then heat resistance is improved, but thermal stress on LED die increases
Solution Approach 1:
The patent optimizes the melting point parameter of the eutectic bonding material to an appropriate range that balances heat resistance with thermal stress reduction. This parameter optimization ensures the bonding material can withstand operating temperatures while minimizing thermal stress on the LED die during bonding.
3Object-affected harmful factors
If low melting point alloy is used for eutectic bonding, then thermal stress is reduced, but bonding layer softens at 70-80°C
Solution Approach 1:
The patent carefully selects and optimizes the melting point parameter of the eutectic bonding material to fall within an appropriate range. This optimization ensures the bonding layer maintains its mechanical strength and contact reliability at operating temperatures of 70-80°C while still providing adequate thermal stress protection during the bonding process.
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 method achieves precise alignment and high luminous efficiency with reduced thermal stress, maintaining alignment and reliability even at elevated temperatures, and allows for batch processing with increased throughput.
Implementation Method 1
a die-bonding material layer (30) is formed on the second metal thin film layer (22), a liquid-solid reaction temperature is applied to respectively form a first intermetallic layer (32) and a second intermetallic layer (34)
Implementation Method 2
a solid-solid reaction temperature is applied for a curing time, so as to complete the bonding
Data Source
AI summary
An LED includes a first intermetallic layer, a first metal thin film layer, an LED chip, a substrate, a second metal thin film layer, and a second intermetallic layer. The first metal thin film layer is located on the first intermetallic layer. The LED chip is located on the first metal thin film layer. The second metal thin film layer is located on the substrate. The second intermetallic layer is located on the second metal thin film layer, and the first intermetallic layer is located on the second intermetallic layer. Materials of the first and the second metal thin film layer are selected from a group consisting of Au, Ag, Cu, and Ni. Materials of the intermetallic layers are selected from a group consisting of a Cu—In—Sn intermetallics, an Ni—In—Sn intermetallics, an Ni—Bi intermetallics, an Au—In intermetallics, an Ag—In intermetallics, an Ag—Sn intermetallics, and an Au—Bi intermetallics.