Copper Ink Oxidation Prevention via Reducing Agents
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Solution Overview
Problem
Current methods for producing conductive patterns using copper nanoparticles are hindered by copper's tendency to oxidize, leading to reduced conductivity and higher processing temperatures, and existing copper compositions are costly due to reliance on complex processes and expensive noble metals like silver.
Innovation Solution
A method involving the formation of a copper ink with copper nanoparticles, where an aqueous solution of copper salt is treated with a surfactant like TERGITOL and a reducing agent, followed by heating and intense pulsed light sintering, to create a conductive copper film without oxides, using lower temperatures and reducing agents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If copper nanoparticles are used to reduce costs compared to silver, then material cost is reduced, but copper oxidizes during sintering leading to reduced conductivity
Solution Approach 1:
A reducing agent is introduced as an intermediary substance that mediates between the copper nanoparticles and oxygen during the sintering process. The reducing agent preferentially reacts with oxygen to prevent copper oxidation, thereby maintaining conductivity while allowing the use of cost-effective copper material
Solution Approach 2:
The sintering process is conducted in an atmosphere controlled to minimize oxidation. By creating a reducing or inert environment during sintering, the copper nanoparticles are protected from oxidizing, maintaining their conductivity while utilizing the cost benefits of copper over silver
2Quantity of substance
If conventional copper ink formulations are used, then material cost is reduced, but higher processing temperatures are required to prevent oxidation
Solution Approach 1:
The chemical environment parameters during sintering are changed from oxidizing to reducing conditions. This parameter change allows the sintering process to occur at lower temperatures without causing copper oxidation, thereby reducing energy consumption while maintaining the cost benefits of using copper
Solution Approach 2:
A reducing agent is added as a chemical intermediary that modifies the sintering environment. This intermediary enables lower temperature processing by preventing oxidation reactions, thus reducing energy requirements while maintaining material cost effectiveness
3Reliability
If reducing agents are added to prevent copper oxidation, then conductivity is maintained, but ink formulation complexity increases
Solution Approach 1:
The ink formulation is designed to be self-protecting against oxidation. The reducing agent is incorporated into the ink matrix in a way that it automatically activates during sintering to protect the copper nanoparticles, eliminating the need for complex external protection systems or multiple processing steps
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 approach results in cost-effective, conductive copper films with reduced oxidation and lower processing temperatures, enabling efficient production of copper-based conductive patterns suitable for applications in printed electronics.
Implementation Method 1
adding an amount of a surfactant, such as TERGITOL, to the aqueous solution to thereby produce a copper ink including a dispersion of copper nanoparticles
Implementation Method 2
adding an amount of a reducing agent to the aqueous solution
Implementation Method 3
heating the aqueous solution to a temperature of about 130° C. to about 150° C.
Implementation Method 4
intense pulsed light sintering, to create a conductive copper film
Data Source
AI summary
The presently-disclosed subject matter includes methods for making a copper ink. In some embodiments the methods comprise forming an aqueous solution that includes copper and adding an amount of a surfactant to the aqueous solution to thereby produce a copper ink that includes a dispersion of copper nanoparticles. In some embodiments the methods further include adding an amount of a reducing agent to the aqueous solution. In some instances the copper inks are formed from copper salts, and in some embodiments the copper inks do not include oxides of copper. The presently-disclosed subject matter also includes copper inks formed by the presently-disclosed methods as well as methods of forming a copper film from a copper ink.