Asymmetric Copper Foil Oxidation for Ceramic Bonding
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Solution Overview
Problem
Conventional methods for bonding copper foils to ceramic substrates are complex and energy-intensive, often resulting in undesired bonds due to the formation of copper oxide layers on both surfaces of the copper foils, leading to inefficient use of heat treatment steps and energy consumption.
Innovation Solution
A method involving wet-oxidation of copper foils to form a copper oxide layer on one surface, with a protective layer on the opposite surface to prevent oxidation, allowing for bonding to a ceramic substrate in a single heat treatment step, using a ceramic-copper foil bonding method that includes roughening and oxidizing solutions to control the oxidation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pre-heating oxidation method is used, then copper oxide layer is formed on copper foil surface, but copper oxide layers form on both opposite surfaces leading to undesired bonds with saggar
Solution Approach 1:
The patent applies local quality by creating asymmetric oxidation where only one surface of the copper foil is oxidized while the other surface remains non-oxidized. This is achieved through selective exposure to oxidation environment, ensuring the copper oxide layer forms only on the bonding surface while the opposite surface stays clean to avoid undesired bonding with the saggar.
Solution Approach 2:
The patent employs asymmetry by designing an oxidation process that treats the two surfaces of the copper foil differently. One surface is exposed to oxidation conditions to form copper oxide layer for bonding, while the other surface is protected or shielded from oxidation, creating an asymmetric structure that prevents undesired bonding with the saggar.
2Reliability
If multiple heat treatment steps are used to bond two copper foils, then bonding quality is improved, but process complexity and energy consumption increase
Solution Approach 1:
The patent merges multiple heat treatment steps into a single integrated bonding process. By preparing the copper foils with asymmetric oxidation beforehand, both copper foils can be bonded to opposite surfaces of the ceramic substrate simultaneously in one heating step, eliminating the need for separate heating cycles and reducing process complexity.
Solution Approach 2:
The patent applies preliminary action by performing selective oxidation of the copper foils before the bonding process. The asymmetric oxidation is completed in advance, so that when the bonding heating is applied, the copper oxide layers are already prepared on the correct surfaces, enabling direct bonding without requiring additional oxidation steps during the bonding process.
3Reliability
If multiple heat treatment steps are used to bond two copper foils, then bonding quality is improved, but energy consumption increases
Solution Approach 1:
The patent combines multiple heating operations into a single energy-intensive bonding step. By preparing the copper foils with asymmetric oxidation beforehand, both foils can be bonded simultaneously in one heating cycle, significantly reducing the total energy consumption compared to performing separate heating operations for each bonding step.
Solution Approach 2:
The preliminary asymmetric oxidation preparation eliminates the need for repeated heating cycles. The oxidation is performed once before bonding, so that the subsequent bonding process requires only a single heating step to achieve both bonds, thereby reducing overall energy consumption.
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 method simplifies the bonding process, reduces energy consumption by allowing two copper foils to be bonded to a ceramic substrate in a single heat treatment step, and avoids undesired bonds with a saggar, thereby improving efficiency and reducing costs.
Implementation Method 1
a copper foil is oxidized such that a surface of the copper foil is oxidized to a copper oxide layer
Implementation Method 2
The copper foil and the ceramic substrate are heated together to a temperature that is lower than 1083°C (the melting point of copper) and higher than 1063°C (the eutectic temperature of the copper-copper oxide eutectic)
Implementation Method 3
The second copper oxide layer 952 of the first copper foil 95 is subsequently reduced to copper
Data Source
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AI summary
A ceramic-copper foil bonding method includes wet-oxidizing a copper foil (1,3,4) such that a surface of the copper foil (1,3,4) is oxidized to a copper oxide layer (11,31,41), contacting the copper oxide layer (11,31,41) with a surface of a ceramic substrate (2,5), and bonding the copper oxide layer (11, 31, 41) of the copper foil (1,3,4) to the surface of the ceramic substrate (2,5) by heat treatment. Preferably, a protective layer is provided on an opposite surface of the copper foil (1,3,4) so that the opposite surface is not oxidized during wet-oxidizing the copper foil (1,3,4).