Base-Metal Conductive Paste Sintering in Air Without Oxidation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current thick-film printing technologies using base metals like copper or copper-nickel alloys require a reducing atmosphere for sintering to prevent oxidation, increasing costs, and existing methods for ceramic parts with external electrodes face issues like shrinkage mismatch and feature changes due to sintering in a restoring atmosphere.
Innovation Solution
The method involves adding 10-90 weight percent metallic aluminum powder to base-metal conductive pastes or alloys to sinter at high temperatures in air, using aluminum's high oxophilicity to prevent oxidation and its strong reduction to restore the metal or alloy, maintaining excellent electrical features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If base metal conductive paste is sintered in air at high temperature, then material cost is reduced, but the base metal oxidizes and loses electrical functionality
Solution Approach 1:
Aluminum powder is introduced as an intermediary substance that preferentially oxidizes to form a protective alumina layer, preventing oxygen from reaching and oxidizing the base metal conductive paste. This mediator approach allows sintering in air while protecting the electrical functionality of the base metal.
Solution Approach 2:
The oxidizing environment, which would normally harm the base metal by causing oxidation and loss of electrical functionality, is converted into a benefit through the aluminum powder's preferential oxidation. The harmful oxygen is consumed by aluminum to form a protective barrier, transforming the oxidizing atmosphere from a threat into a protective mechanism.
2Reliability
If base metal conductive paste is sintered in reducing atmosphere, then oxidation is prevented, but sintering cost significantly increases
Solution Approach 1:
Aluminum powder serves as a chemical intermediary that provides oxidation protection through its preferential reaction with oxygen. This eliminates the need for expensive reducing atmosphere equipment and gas supplies, as the protective function is achieved through the aluminum's chemical behavior in normal air.
Solution Approach 2:
The aluminum powder acts as a consumable protective layer that is sacrificed during sintering to protect the base metal. This disposable approach uses inexpensive aluminum to prevent oxidation, replacing the need for costly reducing atmosphere infrastructure.
3Productivity
If ceramic part and electrode are co-fired, then manufacturing efficiency is improved, but shrinkage mismatch occurs between ceramic and electrode
Solution Approach 1:
The sintering temperature parameter is optimized to a range (900-1400°C) where both the ceramic and the aluminum-containing electrode paste undergo sintering with compatible shrinkage characteristics. By controlling the temperature parameter, the patent achieves coordinated shrinkage of different materials during co-firing, eliminating mismatch while maintaining high manufacturing efficiency.
4Reliability
If sintering temperature is increased to improve electrical features, then conductivity is enhanced, but oxidation risk increases
Solution Approach 1:
The high-temperature oxidizing environment, which would normally degrade electrical features through oxidation, is converted into a beneficial process. The aluminum powder's preferential oxidation at high temperatures creates a protective barrier that enables the base metal to achieve enhanced conductivity while remaining protected from oxidation, even in air atmosphere.
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 allows base metals to be sintered in air without oxidation, reducing material costs significantly while maintaining electrical performance, and prevents shrinkage mismatch in ceramic parts, thus eliminating the need for additional equipment.
Implementation Method 1
the high oxophilicity of said metallic Al powder protecting the thick-film printed base-metal conductive paste or thick-film printed base-metal alloy paste from oxidation on being sintered at the high temperature in the air
Implementation Method 2
the oxidized thick-film printed base-metal conductive paste or thick-film printed base-metal alloy paste is reduced back to a metal or alloy through the strong reduction of the metallic Al powder
Implementation Method 3
process a heat treatment at 500 ̃1400° C. in the air
Data Source
AI summary
A method is provided for sintering base metal or alloy at high temperature in the air. They are used for thick-film printing, where precious metals are completely changed to base metals. Moreover, unlike the current practice where a reduction atmosphere is required to avoid metal oxidization, the present invention is the first to allow very cheap base metals to be sintered at high temperature in the very cheap air while maintaining their excellent electrical features. Therefore, there is no need to change equipment for related industries. The original equipment can still be used for sintering in the air. In other words, it is possible to use base metals instead of precious metals for significantly reducing the material cost. It will lead the world in revolutionary technologies related to using base metals in thick-film printing.