AlN Substrate Brazing with High Silicon Interface for Thermal Reliability
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Solution Overview
Problem
Conventional power module substrates face challenges in achieving high joint strength and thermal cycle reliability due to peeling issues at the interface between metal and ceramics substrates, despite surface roughness reduction techniques.
Innovation Solution
A method involving a ceramics substrate joined to a metal plate using a brazing filler metal with a high silicon concentration at the joint interface, forming a high concentration section with silicon and oxygen, which enhances the joint strength and reliability by diffusing silicon and forming a fusion aluminum layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the surface roughness of the ceramics substrate is reduced to improve joint strength, then the surface smoothness is improved, but peeling occurs at the interface under thermal cycling conditions
Solution Approach 1:
The invention changes the chemical composition parameters at the joint interface by forming a high concentration section with silicon content of 5 wt% or more and oxygen content of 3 wt% or more. This chemical parameter change creates a eutectic structure that improves both joint strength and thermal cycle reliability, resolving the contradiction between smooth surface requirement and peeling prevention under thermal cycling.
Solution Approach 2:
The invention creates a composite structure at the joint interface consisting of a high concentration section with specific silicon and oxygen concentrations. This composite material structure, with controlled composition gradients, provides both the bonding strength needed for smooth surfaces and the thermal stability required to prevent peeling during thermal cycling.
2Temperature
If the power module substrate is rigidly fixed to the heat radiation plate to improve heat radiation efficiency, then the thermal conduction is improved, but large shear force is generated at the joint interface during thermal cycles
Solution Approach 1:
The invention modifies the joint interface composition to include a high concentration section with specific silicon and oxygen content, which creates a eutectic structure. This structural change reduces the shear force at the interface during thermal cycling while maintaining effective heat radiation, resolving the contradiction between thermal performance and mechanical strength.
3Ease of manufacture
If conventional brazing methods are used to join metal plate to ceramics substrate, then the manufacturing process is simple, but sufficient high joint strength is not obtained
Solution Approach 1:
The invention changes the chemical composition parameters in the brazing process by controlling silicon and oxygen concentrations to form a high concentration section at the joint interface. This compositional modification achieves high joint strength using conventional brazing equipment and procedures, maintaining manufacturing simplicity while dramatically improving joint strength.
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 method significantly improves the joint strength and thermal cycle reliability of the power module substrate by creating a high concentration section with silicon and oxygen at the interface, preventing cracks and maintaining reliability under repeated heat stress.
Implementation Method 1
forming a fusion aluminum layer by melting the brazing filler metal
Implementation Method 2
solidifying the fusion aluminum layer
Implementation Method 3
a high concentration section having a silicon concentration that is more than five times the silicon concentration in the metal plate is generated at a joint interface
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
A power module substrate includes: a ceramics substrate (11) composed of AlN. having a top face; a metal plate (22, 23) composed of pure aluminum and joined to the top face of the ceramics substrate (11) with a brazing filler metal (24, 25) including silicon interposed therebetween; and a high concentration section (32) formed at a joint interface (30) at which the metal plate (22, 23) is joined to the ceramics substrate (11), having a silicon concentration that is more than five times the silicon concentration in the metal plate (22, 23).