Insulated Circuit Board with Cu Gradient for Thermal Cycle Resistance
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Solution Overview
Problem
Insulating circuit substrates face challenges in suppressing breaking and deformation of ceramic substrates and aluminum sheets when subjected to severe thermal cycles, requiring improved bonding reliability between ceramic substrates and circuit layers.
Innovation Solution
An insulating circuit substrate is designed with an aluminum sheet laminated to a ceramic substrate, where Cu is solid-solubilized at the bonding interface, maintaining a Cu concentration ratio between the interface and 100 μm depth within specific limits to prevent hard Al—Cu eutectic phase formation, and Al—Cu compound particles are precipitated at crystal grain boundaries to enhance strength and resist deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Cu concentration at bonding interface is increased to improve bonding reliability, then bonding strength between ceramic substrate and aluminum sheet improves, but hard Al-Cu eutectic phase forms causing breaking and deformation under thermal cycles
Solution Approach 1:
The patent applies parameter changes by precisely controlling the Cu concentration distribution in the aluminum sheet. Specifically, the Cu concentration at the bonding interface (A) is maintained at 0.01-5 mass%, and the Cu concentration at 100 μm from the interface (B) is maintained at 0.01-2 mass%, with the ratio B/A being 0.05-2.0. This controlled parameter adjustment ensures sufficient bonding reliability while preventing the formation of excessive hard Al-Cu eutectic phase that would cause breaking and deformation during thermal cycling.
2Reliability
If Cu diffusion into aluminum sheet is increased to enhance bonding strength, then bonding reliability improves, but deformation resistance under thermal cycles deteriorates due to hard phase formation
Solution Approach 1:
The patent applies local quality by creating a non-uniform Cu concentration distribution within the aluminum sheet. The Cu concentration is highest at the bonding interface (A: 0.01-5 mass%) to ensure strong bonding, and gradually decreases toward the interior (B at 100 μm: 0.01-2 mass%). This localized variation in composition allows the bonding interface region to have high bonding reliability while the interior region maintains better resistance to deformation and breaking during thermal cycling.
3Reliability
If bonding strength between ceramic substrate and aluminum sheet is enhanced, then bonding reliability improves, but the aluminum sheet becomes more prone to breaking and deformation under severe thermal cycles
Solution Approach 1:
The patent resolves this contradiction by implementing specific parameter changes in the Cu concentration profile. The Cu concentration at the bonding interface (A) is controlled at 0.01-5 mass% to ensure adequate bonding strength, while the Cu concentration at 100 μm from the interface (B) is controlled at 0.01-2 mass%. The ratio B/A is maintained between 0.05-2.0. This controlled parameter adjustment ensures sufficient bonding reliability while limiting the formation of excessive hard Al-Cu eutectic phase, thereby reducing breaking and deformation under severe thermal cycling conditions.
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 configuration effectively suppresses breaking and deformation of the ceramic substrate and aluminum sheet during thermal cycles while maintaining excellent bonding reliability, ensuring the substrate's integrity under harsh thermal conditions.
Implementation Method 1
Cu is solid-solubilized at a bonding interface between the aluminum sheet and the ceramic substrate
Implementation Method 2
Al—Cu compound particles are precipitated at crystal grain boundaries
Data Source
AI summary
In an insulating circuit substrate, aluminum sheets formed of aluminum or an aluminum alloy are laminated and bonded to a surface of a ceramic substrate and, in the aluminum sheets, Cu is solid-solubilized at a bonding interface with the ceramic substrate and a ratio B/A between a Cu concentration A mass % at the bonding interface and a Cu concentration B mass % at a position of 100 μm in a thickness direction from the bonding interface to the aluminum sheets side is 0.30 or more and 0.85 or less.