Ceramic Circuit Substrate Brazing for Thermal Cycling Resistance
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Solution Overview
Problem
Ceramic circuit substrates with high thermal conductivity, such as aluminum nitride, face challenges with mechanical strength and thermal cycling resistance, leading to cracks and insulation failures when used in power modules under severe loads and thermal conditions.
Innovation Solution
A ceramic circuit substrate is developed with a braze material layer containing Ag, Cu, and active metals like Ti and Zr, with a continuity ratio of 80% or higher and Vickers hardness of 60 to 85 Hv, to enhance bonding performance and thermal cycling resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If aluminum nitride substrates with high thermal conductivity are used, then heat dissipation properties are improved, but mechanical strength and toughness decrease leading to cracks under thermal cycling
Solution Approach 1:
The invention changes the chemical composition parameters of the braze material by adding Group VA elements (V, Nb, Ta) at specific concentrations (0.1-5 mass%) to the traditional Ag-Cu-Ti system. This compositional parameter change modifies the bonding characteristics and mechanical properties of the braze layer, enabling it to provide both strong bonding and crack resistance under thermal cycling conditions while maintaining the high heat dissipation capability of aluminum nitride substrates.
2Temperature
If the ceramic substrate is thinned to improve heat dissipation, then thermal conduction is improved, but stress load during thermal cycling increases causing cracks and insulation failures
Solution Approach 1:
The invention creates a composite braze material system combining Ag-Cu-Ti with Group VA elements (V, Nb, or Ta). This composite material structure leverages the high thermal conductivity of Ag-Cu while the Group VA elements form hard, crack-resistant phases that reinforce the braze layer. The composite nature allows the thin ceramic substrate to maintain both excellent thermal conduction and high reliability under thermal cycling stress.
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 substrate achieves high bonding performance and excellent thermal cycling resistance, with a crack ratio less than 1% after 2000 cycles in heat cycling tests, maintaining operational reliability.
Implementation Method 1
the active metal, Ti, covalently bonds with the N in the nitride ceramic substrate, thereby forming TiN (titanium nitride)
Implementation Method 2
the Vickers hardness of the braze material layer is 60 to 85 Hv, thereby crack resistance can be secured
Data Source
AI summary
A ceramic circuit substrate having high bonding performance and excellent thermal cycling resistance properties, wherein a ceramic substrate and a copper plate are bonded by a braze material containing Ag and Cu, at least one active metal component selected from Ti and Zr, and at least one element selected from among In, Zn, Cd, and Sn, wherein a braze material layer, after bonding, has a continuity ratio of 80% or higher and a Vickers hardness of 60 to 85 Hv.