Crystalline Active Metal Compound Layer for Ceramic-Copper Bonding
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Solution Overview
Problem
The bonding reliability between ceramic and copper members in insulated circuit boards is compromised when ultrasonic waves are applied, particularly due to the fragility of the bonding portion with an Al concentration range of 0.5 at% or more and 15 at% or less, and the potential for cracks starting from an amorphous active metal compound layer.
Innovation Solution
A bonded body is formed with a crystalline active metal compound layer on the ceramic member side, having an Al concentration of 0.15 at% or less in a 0.5 µm to 3 µm thickness range from the interface towards the copper member, and an active metal compound layer thickness of 1.5 nm or more and 150 nm or less, using Al-based ceramics and copper or copper alloys, which improves bonding strength and thermal cycle reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the Al concentration in the bonding portion is set in the range of 0.5 at% or more and 15 at% or less, then the bonding strength between ceramic member and copper member is improved, but the bonding portion becomes fragile and cracks may occur when ultrasonic waves are applied
Solution Approach 1:
The patent applies local quality by creating distinct regions within the bonding portion with different Al concentration ranges. Specifically, it defines a first region (0.5-3μm from active metal compound layer) with Al concentration of 0.5-15 at% for strong bonding, and a second region (3-10μm from active metal compound layer) with Al concentration of 0.05-5 at% for crack resistance. This spatial variation in composition allows each region to fulfill different functional requirements simultaneously.
2Ease of manufacture
If the active metal compound layer is formed amorphously on the ceramic member side, then the bonding process is simplified, but cracks may be generated with the amorphous layer as a starting point when ultrasonic waves are applied
Solution Approach 1:
The patent applies parameter changes by specifying the crystalline state as a critical parameter of the active metal compound layer. By requiring the layer to be crystalline rather than amorphous, the patent changes the structural parameter to eliminate crack initiation sites while maintaining the layer's bonding function. This parameter change directly addresses the reliability issue without fundamentally altering the bonding process.
3Strength
If high temperature heating (1000°C or higher) is applied for DBC bonding, then the bonding between copper sheet and ceramic substrate is achieved, but thermal load may decrease bonding reliability due to ceramic substrate degradation
Solution Approach 1:
The patent applies parameter changes by optimizing the Al concentration distribution parameters within the bonding portion. By controlling the Al concentration to be 0.5-15 at% in the first region and 0.05-5 at% in the second region, the patent modifies the chemical composition parameters to create a bonding structure that achieves strong bonding without requiring excessive thermal load, thereby improving reliability under thermal 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 peeling and cracking between ceramic and copper members even under ultrasonic bonding, enhancing bonding reliability and thermal cycle performance while maintaining excellent insulation and heat resistance.
Implementation Method 1
a terminal material may be bonded with ultrasonic waves
Data Source
Figure 1~2
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AI summary
A bonded body (10) is formed by bonding a ceramic member (11) formed of an Al-based ceramic and a copper member (12) formed of copper or a copper alloy, in which, in a bonding layer (30) formed between the ceramic member (11) and the copper member (12), a crystalline active metal compound layer (31) formed of a compound including an active metal is formed on a ceramic member (11) side, and, the Al concentration is 0.15 at% or less in a thickness range of 0.5 µm to 3 µm from an interface of the active metal compound layer (31) on a copper member (12) side toward the copper member (12).