Silver-Coated Copper Powder Grain Boundary Diffusion
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Solution Overview
Problem
Conductive metal powders like silver and copper face issues with storage stability due to oxidation, particularly at grain boundaries, leading to insufficient reliability in conductive pastes used for electronic components.
Innovation Solution
A metal composite powder is produced by spraying silver-coated copper powder into a thermal plasma tail flame region to diffuse silver into the grain boundaries of copper, followed by additional surface coating with silver, enhancing storage stability by preventing oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper powder is used as conductive material, then cost is reduced and conductivity is improved, but storage stability deteriorates due to oxidation
Solution Approach 1:
The invention uses composite materials by combining copper powder with silver coating and silver diffusion into grain boundaries. This creates a multi-layer protective structure where silver acts as a barrier against oxidation while copper provides conductivity, resolving the contradiction between cost-effective conductive material and oxidation resistance
Solution Approach 2:
The invention creates a protective environment around copper particles by depositing silver on the surface and diffusing it into grain boundaries. This silver-rich environment acts as an inert barrier that prevents oxygen from reaching and oxidizing the copper, effectively isolating the reactive copper surface
2Object-affected harmful factors
If silver-coated copper powder is used, then oxidation resistance is improved, but oxidation proceeds from grain boundaries due to oxygen diffusion
Solution Approach 1:
The invention applies local quality by concentrating silver specifically at the grain boundaries through thermal diffusion. Instead of uniform distribution, silver is targeted to the most vulnerable regions (grain boundaries) where oxidation initiates, providing enhanced local protection where it is most needed
Solution Approach 2:
The invention performs preliminary action by pre-diffusing silver into the grain boundaries before oxidation can occur. The thermal treatment process prepares the microstructure in advance, creating a silver-enriched barrier at grain boundaries that prevents subsequent oxidation attacks
3Reliability
If thermal plasma treatment is applied to diffuse silver into grain boundaries, then oxidation resistance is improved, but additional processing steps are required
Solution Approach 1:
The invention merges two operations into one integrated process: the silver coating deposition and the grain boundary diffusion are combined in a single thermal plasma treatment step. The thermal energy required for diffusion is provided by the plasma process itself, eliminating the need for separate heating and diffusion steps
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 process significantly improves the storage stability and oxidation resistance of the metal composite powder, ensuring reliable performance in conductive pastes by preventing oxidation from both the surface and grain boundaries.
Implementation Method 1
spraying the silver-coated copper powder into a tail flame region of a thermal plasma
Implementation Method 2
cause silver on the surface of the copper powder to diffuse in a grain boundary of copper on the inside of the copper powder
Implementation Method 3
oxidation proceeds from the grain boundaries of copper by the diffusion (grain boundary diffusion) of oxygen along the grain boundaries of copper
Data Source
AI summary
After preparing a silver-coated copper powder wherein the surface of a copper powder having an average particle diameter of 0.1 to 100 μm is coated with silver, the silver-coated copper powder is sprayed into the tail flame region of a thermal plasma to cause silver on the surface of the copper powder to diffuse in the grain boundaries of copper on the inside of the copper powder, and thereafter, the surface of the copper powder is coated with silver to produce a metal composite powder wherein the percentage of the area occupied by silver on a cross section of the metal composite powder is 3 to 20% and wherein the surface thereof is coated with silver.