Sintered Silver Joining Material for High-Temperature SiC Bonding
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Solution Overview
Problem
The existing joining materials for silicon carbide (SiC) power semiconductors at high temperatures suffer from insufficient joining strength due to solvent vaporization and pore formation during the joining process, leading to weak bonding between substrates and chips.
Innovation Solution
A joining material composed of a sintered silver powder with porosity between 8% to 30% and surface roughness between 500 nm and 3.3 μm, produced by heating a dispersion liquid with silver powder and solvent, applying pressure, and optionally polishing or plating, to enhance bonding strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If metal fine particle paste is used for joining at high temperature, then heat resistance is improved, but large pores are generated due to solvent volatilization
Solution Approach 1:
The invention utilizes a sintered body with controlled porosity (8% to 30%) formed by sintering silver powder. This porous structure allows for solvent volatilization during heating while maintaining structural integrity, thereby preventing large pore formation and improving joining quality at high temperatures.
Solution Approach 2:
The invention changes the physical and chemical parameters of the joining material by using a sintered body with specific porosity (8% to 30%) and surface roughness (500 nm to 3.3 μm). These parameter changes enable the material to withstand high temperatures while controlling solvent volatilization effects.
2Manufacturing precision
If joining material is pressurized to suppress pore formation, then pore formation is reduced, but joining strength becomes insufficient
Solution Approach 1:
The sintered body with controlled porosity (8% to 30%) provides a balanced structure that can suppress pore formation during joining while maintaining sufficient joining strength. The porous structure allows for controlled solvent release without compromising the mechanical properties of the joining material.
Solution Approach 2:
The invention uses a composite structure combining sintered silver powder with specific porosity and surface roughness characteristics. This composite material achieves both pore formation suppression and adequate joining strength by integrating multiple functional properties in a single material system.
3Strength
If surface roughness is increased to improve joining strength, then joining strength is improved, but surface quality deteriorates
Solution Approach 1:
The invention optimizes the surface roughness parameter to a specific range (500 nm to 3.3 μm) that balances joining strength improvement with acceptable surface quality. This parameter optimization ensures adequate mechanical interlocking while preventing excessive surface defects.
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 proposed solution achieves a joined body with significantly improved shear strength compared to traditional methods, capable of withstanding high temperatures without melting, and allows for effective joining at temperatures below the melting point of bulk silver.
Implementation Method 1
a sintered body formed by sintering silver powder, in which a porosity of the sintered body is 8% to 30%, and a surface roughness Ra of a joining surface is 500 nm or more and 3.3 μm or less
Implementation Method 2
a method for producing a joining material, the method including a step of heating a coating film formed by using a dispersion liquid of a solvent and silver powder to obtain a sintered body
Data Source
AI summary
In the joined body (10) in which the conductor (12) and the substrate (14) are joined by the joining material (13), the joining material (13) includes a sintered body formed by sintering silver powder. A sintered body having a porosity of 8% to 30% and a surface roughness Ra of a joining surface of 500 nm or more and 3.3 μm or less is adopted.