Spherical Silver Powder with Closed Cavities for Low-Temperature Sintering
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Solution Overview
Problem
Conventional spherical silver powders produced by wet reducing methods require high temperatures to sinter effectively, limiting their ability to form high-density conductive films in electronic components.
Innovation Solution
A method involving the reduction of silver particles in a water reaction system with an aldehyde-based reducing agent while inducing cavitation using ultrasonic waves, resulting in a spherical silver powder with closed cavities that can be fired at lower temperatures, maintaining conductivity and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional wet reducing method is used to produce spherical silver powder, then the particle size can be controlled to be small and uniform, but the powder requires high sintering temperature to form conductive films
Solution Approach 1:
The invention changes the chemical composition parameters of the reducing agent from conventional options (hydrazine, sodium borohydride) to specific aldehydes (formaldehyde, acetaldehyde, propionaldehyde, or butyraldehyde). This parameter change in the reducing agent chemistry fundamentally alters the silver particle formation process, creating particles with internal cavities that enable lower sintering temperatures while maintaining the desired small and uniform particle size distribution
Solution Approach 2:
The invention creates spherical silver powder with closed cavities inside each particle, forming a porous internal structure. These internal cavities increase the surface area and create pathways that facilitate sintering at lower temperatures. The porous structure is formed during the reduction process by controlling the nucleation and growth of silver particles using aldehyde-based reducing agents
2Reliability
If high sintering temperature is used to form conductive films, then good conductivity can be achieved, but energy consumption increases and application to temperature-sensitive substrates is limited
Solution Approach 1:
By changing the reducing agent to aldehydes and controlling the reduction process with cavitation, the invention produces silver particles with modified internal structures that sinter more efficiently. This allows achieving the same conductive film quality at lower temperatures, directly reducing energy consumption while maintaining reliability
Solution Approach 2:
The invention replaces the thermal energy-intensive sintering process with a chemically-modified particle structure that requires less thermal input. The cavitated particle structure acts as a pre-conditioned state that reduces the activation energy needed for sintering, substituting chemical structure optimization for pure thermal processing
3Ease of manufacture
If conventional reducing agents are used, then silver particles can be deposited, but the particles require high temperature for effective sintering
Solution Approach 1:
The invention maintains ease of manufacture by using simple aldehyde-based reducing agents that can be easily mixed with silver nitrate solutions. The key change is in the chemical nature of the reducing agent, which allows the same simple deposition process to produce particles with improved sintering characteristics, eliminating the need for high temperature without complicating the manufacturing process
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 produced spherical silver powder enables the formation of conductive films at reduced temperatures with preserved conductivity and reliability, suitable for use in electronic components like capacitors and solar cells.
Implementation Method 1
depositing silver particles by reduction by mixing the reducing agent containing solution with the water reaction system while causing cavitation in the water reaction system
Implementation Method 2
The cavitation is caused by irradiating the water reaction system containing silver ions with ultrasonic waves
Implementation Method 3
depositing silver particles by reduction by mixing the reducing agent containing solution with the water reaction system
Implementation Method 4
adding a reducing agent to a water reaction system containing silver ions to deposit a spherical silver powder by reduction
Data Source
AI summary
While a water reaction system containing silver ions is irradiated with ultrasonic waves to cause cavitation therein, a reducing agent containing solution, which contains an aldehyde as a reducing agent, is mixed with the water reaction system to deposit silver particles, the solid-liquid separation of which is carried out, and thereafter, the separated silver particles are washed and dried to produce a spherical silver powder which has a closed cavity in each particle thereof.