Active Brazing Paste for Void-Free Metal-Ceramic Bonding
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Solution Overview
Problem
Existing methods for producing metal-ceramics bonded substrates with large bonded areas struggle to sufficiently mitigate bonding defects such as voids and non-bonded portions, which can lead to partial discharge, dielectric breakdown, and impaired heat dissipation.
Innovation Solution
A brazing material in paste form is developed, comprising a powder mixture with titanium powder (0.7-2.0 mass %), copper powder (3-15 mass %), and silver powder as the remaining portion, applied to both surfaces of a ceramic substrate and bonded with a metal plate through heating in a vacuum atmosphere.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the bonded area of metal-ceramics substrate is increased to accommodate more chips, then the power module capacity is improved, but bonding defects such as voids and non-bonded portions increase
Solution Approach 1:
The patent applies local quality by using titanium powder with specific particle size distribution (D50 of 10 μm or less) concentrated at the bonding interface between metal and ceramic. This localized refinement of powder characteristics ensures complete penetration into the bonding interface even in large-area bonded regions, preventing voids and non-bonded portions while maintaining high bonding quality across the entire bonded area.
Solution Approach 2:
The patent changes the particle size parameter of titanium powder to D50 of 10 μm or less, which is significantly finer than conventional powders. This parameter change enables the active metal particles to fully penetrate the bonding interface in large-area bonded regions, ensuring complete bonding without voids while accommodating increased bonded area for higher power module capacity.
2Ease of manufacture
If conventional brazing materials are used in large-area bonded regions, then the bonding process is simple, but bonding defects such as voids and non-bonded portions cannot be sufficiently suppressed
Solution Approach 1:
The patent changes the particle size parameter of titanium powder to D50 of 10 μm or less, which enables complete penetration into the bonding interface. This single parameter change maintains the simplicity of the bonding process while dramatically improving manufacturing precision by eliminating voids and non-bonded portions even in large-area bonded regions.
Solution Approach 2:
The patent uses a composite brazing material containing titanium powder, copper powder, and silver powder in specific proportions. This composite formulation combines the high reactivity of titanium with the excellent electrical and thermal conductivity of copper-silver alloy, achieving complete bonding interface penetration and defect-free bonding while maintaining process simplicity.
3Reliability
If bonding defects are reduced to improve reliability, then partial discharge and dielectric breakdown are suppressed, but the bonded area must be limited
Solution Approach 1:
The patent applies local quality by concentrating fine titanium powder (D50 ≤ 10 μm) at the bonding interface, ensuring complete penetration and void-free bonding. This localized refinement enables large bonded areas to achieve the same bonding quality as small areas, allowing power modules to accommodate more chips while maintaining withstanding voltage of 4 kV or more.
Solution Approach 2:
By changing the particle size parameter to D50 ≤ 10 μm, the patent enables complete penetration into the bonding interface across large areas. This parameter change allows the bonded area to be increased for higher power module capacity while maintaining bonding quality that suppresses partial discharge and ensures withstanding voltage of 4 kV or more.
4Ease of operation
If titanium powder with larger particle diameter is used, then the brazing material is easier to handle, but bonding defects increase in large-area substrates
Solution Approach 1:
The patent changes the particle size parameter to D50 ≤ 10 μm, which is fine enough to ensure complete penetration into the bonding interface in large-area substrates, preventing bonding defects. The use of controlled particle size distribution and appropriate binder formulation maintains adequate paste viscosity and handling characteristics despite the fine particle size.
Solution Approach 2:
The patent creates a composite brazing material where fine titanium powder (D50 ≤ 10 μm) is combined with copper and silver powders in specific proportions. This composite structure maintains adequate flowability and handling properties through the binder system while the fine titanium particles ensure complete penetration and defect-free bonding in large-area applications.
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 effectively suppresses bonding defects in metal-ceramics bonded substrates, even with large bonded areas, thereby enhancing the reliability and performance of power modules by reducing the occurrence of partial discharge and improving heat dissipation.
Implementation Method 1
a bonding technique in which the metal plate and the ceramic substrate are bonded to each other via a brazing material containing an active metal through heating in vacuum, namely an active metal technique
Implementation Method 2
bonded to each other via a brazing material containing an active metal through heating in vacuum
Data Source
AI summary
Provided are a brazing material in paste form containing a powder mixture that contains titanium powder having an average particle diameter (D50) of 20 μm or less in an amount of 0.7 to 2.0 mass %, copper powder in an amount of 3 to 15 mass %, and silver powder as the remaining portion, and a vehicle, and techniques associated with the brazing material.