Power Module Substrate Brazing Oxide Control
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Solution Overview
Problem
Power-module substrates often experience small voids at the bonded interface between the ceramic substrate and metal plate, leading to a risk of separation, especially when bonded using flux-based brazing methods.
Innovation Solution
The solution involves bonding aluminum or aluminum alloy metal plates to ceramic substrates with reduced residual oxides by surface treatment, including etching or blasting to remove wear debris and achieve specific surface roughness, ensuring residual-continuous oxides along the bonded interface are 70% or less in length, and using a metal plate with low oxygen concentration and oxide thickness to prevent void formation and separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If brazing is performed to bond the metal plate and ceramic substrate, then bonding strength is improved, but small voids are generated at the bonded interface
Solution Approach 1:
The metal plate surface undergoes preliminary treatment (etching or blasting) before brazing to remove oxide layers and create a rough surface texture. This preliminary action prepares the surface to minimize void formation during subsequent brazing operations, allowing the brazing process to achieve strong bonding without generating harmful voids at the bonded interface.
Solution Approach 2:
The invention controls the oxide thickness on the metal plate surface within a specific range (5nm to 20nm) through surface treatment. By precisely controlling this parameter, the brazing process can proceed effectively to create strong bonds while preventing excessive void formation that would compromise bonded interface integrity.
2Reliability
If oxide is removed from the metal plate surface before bonding, then void formation is reduced, but bonding strength may be compromised
Solution Approach 1:
Instead of completely removing oxide, the invention controls the oxide thickness within an optimal range of 5nm to 20nm through surface treatment. This parameter control allows sufficient oxide removal to minimize void formation during brazing, while retaining enough oxide to maintain proper bonding characteristics and strength at the metal-ceramic interface.
Solution Approach 2:
The invention replaces aggressive mechanical oxide removal methods with controlled surface treatment processes (etching or blasting) that achieve the desired oxide thickness control. This substitution allows precise control over oxide removal to balance void formation reduction with bonding strength maintenance.
3Ease of manufacture
If flux-based brazing is used to bond the heat sink, then ease of manufacture is improved, but separation risk at the bonded interface increases
Solution Approach 1:
The metal plate surface is preliminarily treated with etching or blasting before flux-based brazing to control oxide thickness to 5nm-20nm. This preliminary preparation enables the use of simple flux-based brazing processes while preventing the oxide-related void formation and separation issues that would otherwise occur with this ease-of-manufacture method.
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
This approach effectively reduces small voids and prevents separation at the bonded interface, enhancing the bonding reliability of power-module substrates by ensuring the residual-continuous oxides are minimized, thereby improving the structural integrity and reliability of the power-module substrate.
Implementation Method 1
The solution involves bonding aluminum or aluminum alloy metal plates to ceramic substrates with reduced residual oxides by surface treatment, including etching or blasting to remove wear debris and achieve specific surface roughness
Implementation Method 2
a power-module substrate according to the present invention is made by bonding a metal plate made of aluminum or aluminum alloy to at least one surface of a ceramic substrate by brazing
Implementation Method 3
it was found out that the oxide remained at the end part of the bonded part tended to be generated by being flowed along with the brazing material which was melted when brazing the ceramic substrate and the metal plate so as to be converged to the end part
Data Source
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AI summary
To provide a power-module substrate and a manufacturing method thereof in which small voids are reduced at a bonded part and separation can be prevented. Bonding a metal plate of aluminum or aluminum alloy to at least one surface of a ceramic substrate by brazing, when a cross section of the metal plate is observed by a scanning electron microscope in a field of 3000 magnifications in a depth extent of 5 µm from a bonded interface between the metal plate and the ceramic substrate in a width area of 200 µm from a side edge of the metal plate, residual-continuous oxide existing continuously by 2 µm or more along the bonded interface has total length of 70% or less with respect to a length of the field.