Copper-Ceramic Bonded Interface for Thermal Cycle Reliability
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Solution Overview
Problem
Insulating circuit substrates face challenges with thermal cycle reliability and braze staining due to thermal stress concentration and bonding material protrusion at the end portions, particularly when copper sheets are bonded to ceramic substrates.
Innovation Solution
The copper/ceramic bonded body sets specific distance and void ratio limits at the bonded interface, along with controlled thickness ratios for active metal and Ag-Cu alloy layers, to enhance strength and prevent material protrusion and breaking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of the bonding layer in the end portion is increased to ensure strength, then the bonding reliability is improved, but the bonding material protrudes out to cause braze staining
Solution Approach 1:
The invention applies different bonding layer thicknesses to different regions: the end portion has a controlled distance (3-30 μm) to prevent protrusion, while the central portion has sufficient bonding material for strong bonding. This local differentiation resolves the contradiction by optimizing each region for its specific function.
Solution Approach 2:
The invention uses a controlled amount of bonding material in the end portion (not excessive) while ensuring sufficient bonding material in the central portion. This partial optimization prevents braze staining at critical edges while maintaining overall bonding strength.
2Temperature
If an overhang part is formed on the circuit layer to increase heat capacity, then the thermal management is improved, but thermal stress is concentrated on the end portion reducing bonding reliability
Solution Approach 1:
The invention creates a localized reinforcement zone at the end portion with controlled bonding layer thickness (3-30 μm distance) to specifically address thermal stress concentration, while the rest of the structure maintains its heat capacity functions.
Solution Approach 2:
The invention preemptively designs the bonding layer thickness in the end portion to cushion against future thermal stress during thermal cycling, preventing bonding failure before it occurs.
3Reliability
If the bonding material is increased to ensure bonding strength, then the thermal cycle reliability is improved, but the bonding material protrudes out causing braze staining
Solution Approach 1:
The invention applies sufficient bonding material in the central portion for thermal cycle reliability while controlling the bonding layer thickness at the end portion (3-30 μm distance) to prevent protrusion and braze staining.
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 improves thermal cycle reliability and suppresses braze staining, ensuring robust bonding without significant hardness differences at the interface.
Implementation Method 1
the copper sheet is disposed on one surface of the ceramic substrate and the other surface thereof with Ag—Cu—Ti-based brazing material being interposed, and then a heating treatment is carried out to bond the copper sheet (so-called active metal brazing method)
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 at a bonded interface between the ceramic member and each of the copper members, the distance between the ceramic member and each of the copper members in an end portion of each of the copper members is in a range of 3 μm or more and 30 μm or less, and a void ratio in an end portion region (E) of each of the copper members is 10% or less.