Conductive Thin Film on Low Temperature Substrates
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Solution Overview
Problem
Current methods for forming conductive traces on electronic circuits require high-temperature substrates, limiting the use of inexpensive materials like paper or plastic due to the need for high-temperature sintering and inert atmospheres, which increase processing costs and time.
Innovation Solution
A method involving the dispersion of a reducible metal compound and a reducing agent on a low-temperature substrate, followed by exposure to pulsed electromagnetic emissions to initiate a redox reaction, allowing for rapid reduction and sintering of metal oxides in an ambient atmosphere.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-temperature sintering is used to form conductive traces, then electrical conductivity is improved, but substrate temperature requirement increases and processing cost increases
Solution Approach 1:
The patent changes the chemical state of copper from metallic copper to copper oxide, which enables sintering at lower temperatures (below 200°C) while still achieving good electrical conductivity. This parameter change in chemical composition allows the use of low-temperature substrates like paper and plastic that would otherwise decompose at high sintering temperatures.
Solution Approach 2:
The patent utilizes the phase transition of copper oxide reduction to metallic copper during the sintering process. By controlling the reduction atmosphere and temperature, copper oxide particles transform into conductive metallic copper structures at temperatures suitable for low-temperature substrates, achieving conductivity without requiring traditional high-temperature sintering.
2Quantity of substance
If copper particles are used instead of silver, then material cost is reduced, but oxidation resistance worsens and processing complexity increases
Solution Approach 1:
The patent applies preliminary oxidation to copper particles before printing, converting them to copper oxide. This preliminary action prevents oxidation issues during the sintering process, as copper oxide is stable and will reduce to metallic copper under controlled conditions. This eliminates the need for complex inert atmosphere processing while maintaining copper's cost advantage.
Solution Approach 2:
Instead of trying to prevent copper oxidation during sintering (the conventional approach), the patent inverts the strategy by pre-oxidizing the copper particles. This inversion simplifies the manufacturing process, as the oxidation state is already controlled before printing, and the reduction to metallic copper occurs naturally during the low-temperature sintering process in ambient or controlled atmospheres.
3Quantity of substance
If low-temperature substrates are used, then material cost is reduced, but processing time increases and film resistivity increases
Solution Approach 1:
The patent changes the chemical composition from metallic copper to copper oxide, which fundamentally alters the sintering behavior. Copper oxide particles can be sintered at low temperatures (below 200°C) in very short times (seconds to minutes), achieving both low substrate temperature and high processing speed. This parameter change resolves the contradiction between substrate temperature and processing efficiency.
4Reliability
If inert or reducing atmosphere is used for sintering, then electrical conductivity is improved, but processing cost and equipment complexity increase
Solution Approach 1:
The patent employs a self-reducing mechanism where copper oxide particles reduce to metallic copper through controlled thermal decomposition or reaction with trace organic materials present in the ink formulation. This self-service approach eliminates the need for external reducing gases or complex atmosphere control systems, while still achieving high electrical conductivity. The reduction process is self-contained within the printed ink layer.
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
Enables the rapid formation of highly conductive thin films on low-temperature substrates like paper or plastic, reducing processing time and costs, while avoiding the need for inert atmospheres, thus achieving conductivities comparable to silver at lower material costs.
Implementation Method 1
The thin film along with the substrate is subsequently exposed to a pulsed electromagnetic emission to chemically react with the reducible metal compound and the reducing agent
Implementation Method 2
to chemically react with the reducible metal compound and the reducing agent such that the thin film becomes electrically conductive
Implementation Method 3
the substrate is then heated to sinter the particles of the metallic ink in order to form electrical conducting traces
Data Source
AI summary
A method for producing an electrically conductive thin film on a substrate is disclosed. Initially, a reducible metal compound and a reducing agent are dispersed in a liquid. The dispersion is then deposited on a substrate as a thin film. The thin film along with the substrate is subsequently exposed to a pulsed electromagnetic emission to chemically react with the reducible metal compound and the reducing agent such that the thin film becomes electrically conductive.