Porous Sintered Silver Joining Material for SiC Bond Strength
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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 porosity issues when used for substrate-chip bonding.
Innovation Solution
A joining material composed of a sintered silver powder with specific porosity (8-30%) and surface roughness (1.06-3.3 μm) is developed, which includes a combination of silver particle groups with different diameters and surface plating with metals like silver, copper, tin, or nickel 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 (8-30%) as the joining material. This porous structure allows for solvent volatilization during sintering without forming large harmful pores, while maintaining sufficient density for strong bonding. The porosity acts as a buffer that accommodates gas evolution during the heating process.
Solution Approach 2:
The invention changes the physical and chemical parameters of the joining material by using a sintered body with specific porosity (8-30%) and surface roughness (500 nm to 3.3 μm). These parameter changes enable the material to withstand high temperatures while preventing large pore formation through controlled microstructure.
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 (8-30%) provides a unique structure that prevents large pore formation during joining without requiring excessive pressurization. The porous structure naturally accommodates solvent volatilization, eliminating the need for high pressure that would compromise joining strength.
Solution Approach 2:
The invention utilizes surface roughness (500 nm to 3.3 μm) of the sintered body to enhance mechanical interlocking between the joining material and substrates. The rough surface topology provides anchoring effects that strengthen the bond without requiring additional pressurization.
3Stability of the object's composition
If solvent content is increased to improve dispersion, then dispersion quality is improved, but large pores are generated during heating
Solution Approach 1:
The sintered body with controlled porosity (8-30%) serves as a pre-formed structure that can accommodate solvent content without generating large pores during heating. The porous network provides pathways for solvent evacuation while maintaining structural integrity.
Solution Approach 2:
The joining material is pre-sintered to form a stable porous structure before the actual joining process. This preliminary sintering creates a robust framework that prevents large pore formation even when solvent content is increased for better dispersion of metal particles.
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 new joining material achieves superior shear strength and stability at high temperatures, effectively addressing the limitations of previous materials by maintaining bonding integrity and strength across a range of conditions.
Implementation Method 1
containing a sintered body formed by sintering silver powder
Implementation Method 2
the solvent volatilizes at the time of joining and large pores (voids) are generated
Data Source
Figure 1~2B
Figure 2C~2E
Figure 3A~3B
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.