Palladium Conductive Ink for Low-Temperature Substrate Compatibility
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Solution Overview
Problem
Existing conductive ink compositions, particularly those based on silver, require high temperatures for conversion and are not stable at room temperature, making them incompatible with flexible substrates and prone to particle precipitation, while seeking a cheaper alternative with lower conversion temperatures and improved stability.
Innovation Solution
Development of palladium-based ink compositions using a palladium salt, a complexing agent, and a short chain carboxylic acid or its salt, which allows for the formation of conductive palladium structures at temperatures of 120° C. or less, ensuring stability and compatibility with various substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silver-based conductive ink compositions are used, then high electrical conductivity can be achieved, but high conversion temperatures are required and they are not stable at room temperature
Solution Approach 1:
The patent changes the chemical composition parameters by substituting silver-based precursors with palladium-based precursors and adjusting the ligand system. This parameter change enables the ink to achieve stable room temperature storage while reducing the conversion temperature to below 150°C, resolving the contradiction between stability and conversion temperature requirements.
Solution Approach 2:
The patent employs a disposable precursor complex system that is stable during storage but converts completely to metallic palladium during processing. The organic ligands and stabilizers are designed to be consumed during the reduction process, providing stability when needed and enabling conversion when processed, thus resolving the stability-conversion temperature contradiction.
2Reliability
If silver-based conductive ink compositions are used, then high electrical conductivity can be achieved, but particle precipitation occurs when stored at room temperature for over 2 to 3 days
Solution Approach 1:
The patent introduces palladium-based precursor complexes with specific organic ligands as intermediaries that remain stable in solution during storage. These intermediary compounds prevent direct precipitation of metallic particles during storage, yet can be converted to conductive metallic palladium during controlled processing, thus eliminating the harmful precipitation effect while maintaining storage stability.
Solution Approach 2:
The patent changes the chemical parameters by using palladium salts with specific ligand systems that alter the solubility and stability characteristics. This parameter change prevents particle precipitation during room temperature storage while maintaining the ability to convert to conductive form during processing, resolving the contradiction between storage stability and particle formation.
3Reliability
If high temperatures are used to form conductive coatings, then electrical conductivity can be improved, but compatibility with plastic and paper substrates is lost
Solution Approach 1:
The patent changes the thermal processing parameters by developing a palladium-based ink system that achieves full conversion and bulk conductivity at temperatures below 150°C. This parameter change enables compatibility with temperature-sensitive substrates like plastic and paper while still achieving the required electrical conductivity, resolving the contradiction between conductivity and substrate compatibility.
Solution Approach 2:
The patent employs a disposable low-temperature processing approach where the precursor complex completely converts to metallic palladium during a mild heating process. This single-use, low-temperature conversion process eliminates the need for high temperature exposure, thereby protecting temperature-sensitive substrates while still achieving conductive coatings.
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 palladium-based ink compositions are highly conductive, stable at room temperature for extended periods, and suitable for a range of patterning techniques, achieving bulk conductivity upon mild annealing, thus overcoming the limitations of silver-based inks.
Implementation Method 1
a complex comprising a complexing agent and a short chain carboxylic acid or salt thereof
Implementation Method 2
can be reduced to elemental form at a temperature lower than what is needed to reduce a silver salt
Implementation Method 3
achieving bulk conductivity upon mild annealing
Data Source
AI summary
Disclosed herein are ink compositions for making a conductive palladium structure. For example, the ink composition can comprise a palladium salt and a complex of a complexing agent and a short chain carboxylic acid or salt thereof. In some embodiments, a second or third metal salt is included in the compositions. Also disclosed herein are methods for making and using such conductive ink compositions.