Conductive Paste with Hydrophilic Coating for High Conductivity
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Solution Overview
Problem
Conductive pastes used in electronic devices face challenges in achieving high electric conductivity due to the inherent lower conductivity of heat curable resins and the high resistivity of spherical metal powders, which limits the performance of thinner and finer electrodes and wiring patterns.
Innovation Solution
A heat curable conductive paste is developed with a conductive powder coated with an aliphatic polyvalent carboxylic acid and a mixture of bifunctional or higher polyfunctional and monofunctional epoxy resins, optimizing the arrangement to reduce the presence of epoxy resin at particle contacts, thereby increasing conductivity while maintaining adhesiveness and heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat curable resin is used in conductive paste, then adhesiveness and heat resistance are improved, but electric conductivity deteriorates
Solution Approach 1:
The patent applies local quality by creating hydrophilic conductive powder particles with specific surface properties that locally repel hydrophobic epoxy resin. This causes the resin to be excluded from the contact regions between conductive particles, creating zones of high conductivity at particle interfaces while maintaining overall adhesive properties through the resin in non-contact regions.
Solution Approach 2:
The patent uses an intermediary mechanism where the hydrophilic surface treatment on conductive powder acts as a mediator between the conductive particles and the hydrophobic epoxy resin. This surface treatment creates a repulsive interaction that prevents resin accumulation at particle contacts, allowing the conductive particles to maintain direct contact and high conductivity while the resin provides adhesion elsewhere.
2Ease of manufacture
If spherical metal powder is used, then ease of manufacture is improved, but electric conductivity deteriorates due to high resistivity
Solution Approach 1:
The patent applies parameter changes by modifying the surface properties of spherical metal powder particles through hydrophilic treatment. This changes the surface energy and wettability parameters, causing the particles to repel hydrophobic epoxy resin. The spherical shape is maintained for ease of manufacture, but the surface parameter modification enables better electrical contact by preventing resin accumulation at particle interfaces.
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 solution results in a conductive coating with enhanced electric conductivity, adhesiveness, and heat resistance, effectively reducing resistivity and ensuring consistent formation of reliable coatings, especially with spherical silver powders, even at lower drying temperatures.
Implementation Method 1
an aliphatic polyvalent carboxylic acid is adhered on a surface of a powdered metal core
Implementation Method 2
the conductive powder surface will repel the hydrophobic epoxy resin
Implementation Method 3
dried by heating at a relatively low temperature (typically 100° C. to 300° C., e.g. 100° C. to 200° C.) to cure the heat curable resin
Data Source
AI summary
Provided is a heat curable conductive paste used to form a conductive coating. The heat curable conductive paste comprises a conductive powder, a heat curable epoxy resin and a curing agent. In the conductive powder, an aliphatic polyvalent carboxylic acid is adhered on a surface of a powdered metal core. The epoxy resin comprises a bifunctional or higher polyfunctional epoxy resin and a monofunctional epoxy resin, and the polyfunctional epoxy resin and the monofunctional epoxy resin have a mass ratio of 90:10 to 20:80.