Core-Shell Metal Particles for Low-Temperature Semiconductor Bonding
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Solution Overview
Problem
There is a need for metal particles for adhesive pastes that can be used at low temperatures (200°C or less) to reduce defects and performance degradation in highly integrated semiconductor packages, while also maintaining uniform size and preventing aggregation.
Innovation Solution
The development of metal particles with a core-shell structure, where the core has a higher melting point than the shell, and the particles are designed to have a uniform size with a specific particle size distribution and a shell thickness of 10 nm to less than 100 μm, preventing aggregation and ensuring uniform bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If traditional solder materials are used for mounting, then strong bonding is achieved, but thermal damage occurs to semiconductor devices at high temperatures
Solution Approach 1:
The solder particle is divided into core and shell segments. The core contains high-melting-point metal materials (Sn, Ag, Cu) for structural integrity, while the shell contains low-melting-point metal materials (In, Ga, Bi) that melt at lower temperatures to enable bonding. This segmentation allows the particle to function at low mounting temperatures without requiring the entire material to have low melting point, thus preventing thermal damage to semiconductor devices while maintaining bonding reliability.
Solution Approach 2:
The invention uses composite metal particles with a core-shell structure combining different metal materials with different melting points. The composite structure integrates the advantages of high-melting-point materials (strength, stability) and low-melting-point materials (low-temperature processing), enabling low-temperature mounting that prevents thermal damage while maintaining strong bonding through the intermetallic compound layer formed at the core-shell interface.
2Manufacturing precision
If metal particles with varying sizes are used, then manufacturing flexibility is improved, but uniform bonding cannot be achieved
Solution Approach 1:
The invention controls the particle size parameter within a specific range (1 μm to 60 μm, preferably 5 μm to 50 μm) and maintains a narrow size distribution (D90/D10 ratio of 1.05 to 1.30). This parameter control ensures uniform bonding behavior and consistent intermetallic compound formation, while the core-shell structure design allows flexibility in selecting specific size values within this range for different application requirements.
Solution Approach 2:
The shell thickness is controlled to be 10 nm to less than 100 μm, creating a specific local quality ratio between shell and core. This controlled shell thickness ensures sufficient low-melting-point material for bonding while maintaining the structural integrity of the core, and this local quality control contributes to uniform bonding across particles of various sizes within the specified size range.
3Temperature
If core-shell metal particles are used to enable low-temperature mounting, then thermal damage is reduced, but particle aggregation may occur
Solution Approach 1:
The shell acts as a flexible protective layer that prevents direct contact between core particles, reducing aggregation. The thin film structure (10 nm to less than 100 μm thickness) provides sufficient barrier effect to maintain particle dispersion while being thin enough to allow the low-melting-point materials to function effectively during bonding, thus preventing thermal damage without causing aggregation.
Solution Approach 2:
The shell material acts as an intermediary layer between core particles, preventing direct aggregation while allowing the intended bonding function. The low-melting-point shell materials (In, Ga, Bi) serve as a mediator that enables low-temperature bonding through controlled melting and intermetallic compound formation, while simultaneously preventing unwanted aggregation during the mounting 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 core-shell metal particles effectively reduce defects in semiconductor packages by allowing low-temperature mounting without re-melting during subsequent heat treatments, and they provide uniform bonding with reduced physical property differences compared to traditional solder materials.
Implementation Method 1
An intermetallic compound can be formed between the one or more metal materials of the core and the one or more metal materials of the shell
Implementation Method 2
The one or more metal materials of the core may have a melting point higher than that of the one of more metal materials of the shell
Data Source
AI summary
Provided are metal particles for an adhesive paste, a solder paste composition including the same, and a method of preparing the metal particles for an adhesive paste. The metal particles for an adhesive paste may include a core including one or more metal materials; and a shell arranged on part or an entirety of the core and including one or more metal materials. The metal material of the core may have a melting point higher than that of the metal material of the shell. An intermetallic compound is capable of being formed between the metal material of the core and the metal material of the shell. A ratio (D90/D10) of the 90% cumulative mass particle size distribution (D90 size) to the 10% cumulative mass particle size distribution (D10 size) in a particle size distribution of the metal particles may be 1.22 or less.