Copper-Ceramic Bonded Substrate Edge Composition for Thermal Cycling
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Solution Overview
Problem
Insulating circuit substrates face challenges with thermal cycle reliability due to concentrated thermal stress at the edge of the circuit layer, leading to decreased bonding reliability and potential breaking, especially with the use of Ag-containing bonding materials that undergo solid solution hardening.
Innovation Solution
A copper/ceramic bonded body is designed with an edge region of the copper member having an Ag solid solution part concentration of 0.5% to 15% by mass, area ratio of 0.03 to 0.35, and a specific thickness range for active metal compound and Ag-Cu alloy layers to enhance bonding reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Ag is contained in the bonding material at the edge of the copper member, then bonding strength is improved, but solid solution hardening occurs causing thermal stress concentration and reduced thermal cycle reliability
Solution Approach 1:
The patent applies local quality by creating a non-uniform Ag distribution in the edge region of the copper member. Specifically, the Ag concentration is controlled to be 5-20 wt%, and the area ratio of Ag solid solution is controlled to be 0.03-0.35, which is lower than in conventional technologies. This local control prevents excessive hardening at the edge while maintaining sufficient bonding strength, thereby resolving the contradiction between bonding strength and thermal cycle reliability.
Solution Approach 2:
The patent changes the parameters of Ag concentration and area ratio of Ag solid solution in the edge region. By controlling Ag concentration to 5-20 wt% and area ratio to 0.03-0.35, the patent optimizes the balance between bonding strength and resistance to thermal stress. This parameter optimization prevents solid solution hardening while ensuring adequate bonding, thus improving thermal cycle reliability without sacrificing bonding strength.
2Reliability
If an overhang part is formed on the circuit layer, then insulating properties are ensured and heat capacity is increased, but thermal stress is concentrated on the edge causing bonding reliability to decrease
Solution Approach 1:
The patent applies local quality by treating the edge region differently from the central region. In the edge region (within 100 μm from the edge), the Ag concentration is controlled to 5-20 wt% and area ratio to 0.03-0.35, which is more stringent than in the central region. This local differentiation allows the overhang structure to maintain its insulating and heat capacity benefits while preventing thermal stress concentration at the critical edge region, thus preserving bonding reliability.
3Strength
If the edge of the copper member is hardened by solid solution hardening, then strength is increased, but thermal stress concentration occurs leading to ceramic breaking under thermal cycle
Solution Approach 1:
The patent changes the parameters of Ag concentration and area ratio to prevent excessive hardening. By controlling Ag concentration to 5-20 wt% and area ratio of Ag solid solution to 0.03-0.35 in the edge region, the patent achieves optimal hardness that provides sufficient strength while avoiding excessive hardening that would cause thermal stress concentration. This parameter control prevents ceramic breaking during thermal cycling while maintaining adequate edge 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 solution effectively suppresses hardening and peeling, ensuring robust thermal cycle reliability by firmly bonding the ceramic and copper components, preventing breaking even under severe thermal cycles.
Implementation Method 1
Ag contained in the bonding material undergoes solid solution to be subject to solid solution and hardening
Data Source
AI summary
The copper/ceramic bonded body according to the present invention is a copper/ceramic bonded body obtained by bonding copper members consisting of copper or a copper alloy to a ceramic member, where in an edge region E of each of the copper members, an area ratio of each of Ag solid solution parts having an Ag concentration of 0.5% by mass or more and 15% by mass or less is set in a range of 0.03 or more and 0.35 or less.