Copper Conductive Paste Air Firing via Carbon Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Copper, a cost-effective conductive material, cannot be fired in air due to oxidation, increasing capital investment, while precious metals like silver can be fired in air but are expensive, necessitating a solution that uses inexpensive copper, allows air firing, and achieves low electrode resistance.
Innovation Solution
A copper-containing conductive paste comprising 10-95 wt% of a powder mixture of Cu, Ge, and B particles, with 0.1-15 wt% glass frit dispersed in an organic medium, enabling firing in air and achieving low electrode resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If copper powder is used as conductive material, then material cost is reduced, but firing must be performed under nitrogen atmosphere increasing capital investment
Solution Approach 1:
An organic polymer is introduced as an intermediary substance that releases carbon during firing to create a reducing atmosphere locally around the copper particles. This allows copper to be fired in air without oxidation, as the carbon from the polymer decomposition protects the copper from oxygen while the overall atmosphere remains air-based rather than requiring nitrogen filling
Solution Approach 2:
The invention changes the chemical composition parameters of the conductive paste by adding specific organic polymers with controlled carbon content (30-70 wt% of total paste weight). This parameter change enables the paste to self-generate a reducing environment during firing, transforming the firing process from requiring external nitrogen atmosphere to being performable in air
2Ease of manufacture
If precious metals like silver are used, then firing can be performed in air, but material cost increases sharply
Solution Approach 1:
The invention replaces expensive precious metals (silver, gold, palladium) with inexpensive copper powder combined with an organic polymer that serves as a temporary, consumable protective agent. The polymer is consumed during firing to provide temporary protection, after which it decomposes completely, leaving only the copper conductive path. This substitutes durable expensive materials with cheap consumable protective materials
Solution Approach 2:
The invention creates a composite conductive paste material consisting of copper powder (conductive component) combined with organic polymer (protective component). This composite material exhibits dual functionality: copper provides electrical conductivity while the organic polymer provides oxidation protection during firing. The synergistic combination achieves properties that neither component could provide alone
3Quantity of substance
If copper is used without protective atmosphere, then material cost is reduced, but copper oxidizes during firing increasing electrode resistance
Solution Approach 1:
The organic polymer is incorporated into the conductive paste formulation before the firing process begins. This preliminary incorporation ensures that when firing occurs, the polymer is already positioned around the copper particles and will decompose at the appropriate time to provide carbon-based protection. The protective action is pre-prepared and automatically activated during firing without requiring additional steps
Solution Approach 2:
The invention converts the typically harmful effect of organic materials (combustion/oxidation during firing) into a beneficial protective effect. By carefully selecting organic polymers with appropriate carbon content and decomposition characteristics, the combustion process generates carbon monoxide and carbon that form a protective reducing atmosphere around copper particles, preventing oxidation. The harmful combustion is thus transformed into a beneficial protective mechanism
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 paste allows for the use of inexpensive copper, reduces material costs, and produces electrodes with low resistivity, even when fired in air, by preventing copper oxidation and accelerating sintering with Ge and B particles.
Implementation Method 1
an organic polymer which releases carbon when burned is dissolved in a solvent
Implementation Method 2
copper cannot be fired in air because it oxidizes easily
Implementation Method 3
These circuits are then dried and fired to volatilize and burn out the liquid organic medium and sinter the metal particles
Data Source
AI summary
Disclosed herein are copper-containing (Cu-containing) conductive pastes, copper (Cu) electrodes formed by firing the Cu-containing conductive paste over a substrate, and articles comprising a structural element with such Cu electrodes, wherein, the Cu-containing conductive paste contains a powder mixture of Cu, Ge, and B particles dispersed in an organic medium.