Low-Oxygen Copper Powder via Inert Water Atomization
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Solution Overview
Problem
Conventional copper powders used in conductive pastes for forming contact members on ceramic or dielectric substrates face issues with oxygen content increase when particle diameter is reduced, leading to lower shrinkage starting temperatures and increased differences in shrinkage rates with the substrate, resulting in separation or cracking. Additionally, existing methods for producing fine copper particles are inefficient and costly.
Innovation Solution
A method involving rapid cooling and solidification of molten copper by spraying high-pressure water in a non-oxidizing atmosphere, which produces copper powder with a low oxygen content and high shrinkage starting temperature, even at small particle diameters, by heating the molten copper above its melting point and allowing it to drop while being sprayed with high-pressure water.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the particle diameter of copper powder is decreased to form a thin copper layer, then the ability to form thin conductive layers is improved, but the oxygen content increases and shrinkage starting temperature decreases
Solution Approach 1:
The patent applies inert atmosphere by conducting the water atomization process in a nitrogen or argon atmosphere. This prevents oxidation of the copper powder particles during production, maintaining low oxygen content even when particle diameter is reduced to 10 μm or less. The inert gas environment excludes oxygen from contact with the molten copper during atomization, thereby preserving the shrinkage starting temperature while enabling fine particle formation.
2Manufacturing precision
If conventional water atomizing method is used to produce fine copper particles, then particle diameter is reduced, but oxygen content increases and shrinkage starting temperature lowers
Solution Approach 1:
The patent employs an inert atmosphere (nitrogen or argon) during the water atomization process to prevent oxidation of copper particles. This allows production of fine copper powder with controlled particle diameter (10 μm or less) while maintaining oxygen content at 0.5 wt% or less. The inert gas environment eliminates oxygen contact during the critical atomization stage, resolving the contradiction between achieving fine particle size and preventing oxygen contamination.
3Reliability
If copper powder with high shrinkage starting temperature is used, then the difference in shrinkage rate with ceramic substrate is decreased, but production cost increases due to specialized processes
Solution Approach 1:
The patent achieves high shrinkage starting temperature (600°C or higher) copper powder through water atomization in inert atmosphere, which prevents oxidation and maintains material purity. This approach produces copper powder with excellent shrinkage characteristics compatible with ceramic substrates while avoiding the need for expensive alternative processes. The method maintains ease of manufacture by using standard water atomization equipment modified with inert gas supply, rather than requiring specialized high-cost production facilities.
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 method produces copper powder with a low oxygen content and high shrinkage starting temperature, enabling the formation of conductive films with improved conductivity and reduced substrate separation or cracking, while being cost-effective and efficient.
Implementation Method 1
rapidly cooling and solidifying by spraying a high-pressure water onto the heated molten metal
Implementation Method 2
rapidly cooling and solidifying the heated molten metal by spraying a high-pressure water onto the heated molten metal
Data Source
AI summary
There are provided an inexpensive copper powder, which has a low content of oxygen even it has a small particle diameter and which has a high shrinkage starting temperature when it is heated, and a method for producing the same. While a molten metal of copper heated to a temperature, which is higher than the melting point of copper by 250 to 700° C. (preferably 350 to 650° C. and more preferably 450 to 600° C.), is allowed to drop, a high-pressure water is sprayed onto the heated molten metal of copper in a non-oxidizing atmosphere (such as an atmosphere of nitrogen, argon, hydrogen or carbon monoxide) to rapidly cool and solidify the heated molten metal of copper to produce a copper powder which has an average particle diameter of 1 to 10 μm and a crystallite diameter Dx(200) of not less than 40 nm on (200) plane thereof, the content of oxygen in the copper powder being 0.7% by weight or less.