Spherical Silver Powder with Internal Voids for Low-Temperature Sintering
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Solution Overview
Problem
Existing silver powders used in conductive pastes lack excellent printability and low-temperature sintering ability, which are essential for forming conductive patterns and electrodes without degrading peripheral components during firing.
Innovation Solution
A method of producing spherical silver powder by causing a silver-containing solution to flow in a channel, adding a complexing agent partway along the channel, and then adding formalin downstream to induce reduction precipitation, resulting in particles with voids and a controlled D50/DBET ratio of 0.9 to 1.2, enhancing dispersibility and low-temperature sintering ability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional silver powder production methods are used, then silver powder can be produced, but the powder lacks excellent printability and low-temperature sintering ability
Solution Approach 1:
The invention changes the physical and chemical parameters of silver powder by controlling the reduction precipitation process in a flowing liquid state within a channel. By adjusting flow rates, addition positions of complexing agents and reductants, and reaction conditions, the invention produces spherical particles with voids and controlled size distribution (D50/DBET ratio of 0.95-1.05), achieving both excellent printability and low-temperature sintering ability while maintaining uniform particle morphology and dispersibility
Solution Approach 2:
The invention intentionally creates spherical silver powder particles containing voids in their internal structure. These porous particles are formed through controlled reduction precipitation where the liquid state reaction allows formation of hollow or void-containing spherical structures. The porous structure reduces particle density and improves sintering behavior, enabling low-temperature sintering while maintaining good printability and dispersibility in conductive paste
2Volume of moving object
If silver powder with small particle diameter is used, then compactization of electronic components is improved, but dispersibility and sintering ability deteriorate
Solution Approach 1:
The invention changes the particle morphology parameters by producing spherical silver powder with controlled size distribution through flow-controlled reduction precipitation. The spherical shape with voids and narrow size distribution (D50/DBET ratio of 0.95-1.05) achieved through this method improves both dispersibility and sintering ability while maintaining small particle diameter, resolving the contradiction between particle size reduction and functional performance
3Reliability
If high firing temperature is used, then sintering ability is improved, but degradation of peripheral members occurs
Solution Approach 1:
The invention creates spherical silver powder with internal voids that facilitate low-temperature sintering. The porous structure provides higher surface area and better contact between particles, enabling effective sintering at lower temperatures (600-750°C). This resolves the contradiction by achieving good sintering ability without requiring high firing temperatures that would degrade peripheral members such as organic vehicles and glass frit in conductive paste
Solution Approach 2:
The invention changes the sintering temperature parameter from conventional high temperatures to low temperatures (600-750°C) by producing silver powder with optimized spherical morphology and void structure. This parameter change enables adequate sintering ability while avoiding thermal degradation of heat-sensitive peripheral members in the conductive paste system
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 exhibits excellent printability and low-temperature sintering ability, suitable for conductive pastes used in electronic components, enabling high-density patterning and reducing thermal stress.
Implementation Method 1
causing a silver-containing solution to flow in a channel
Implementation Method 2
adding a complexing agent partway along the channel
Implementation Method 3
adding formalin downstream to induce reduction precipitation
Implementation Method 4
adding formalin downstream to induce reduction precipitation
Data Source
AI summary
Provided is a spherical silver powder that can bring about excellent printability and low-temperature sintering ability when used in a conductive paste or the like. The spherical silver powder has a ratio D50/DBET of a diameter D50 at a volume-based cumulative value of 50% according to laser diffraction relative to a BET diameter DBET of not less than 0.9 and not more than 1.2 and includes voids in inner parts of particles.