Silver Powder Surface Smoothing for Low-Temperature Conductive Pastes
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Solution Overview
Problem
Conductive pastes used in electronic components face challenges in achieving low-temperature firing with high electrical conductivity and low susceptibility to wire disconnection, especially during the thinning process, due to the presence of voids in fine silver particles which lead to surface irregularities and agglomeration.
Innovation Solution
A method involving multiple surface smoothing steps with mechanical collision and high-pressure airflow to remove fine powder, resulting in silver powders with internal voids and smooth surfaces, reducing surface roughness and agglomeration, and enhancing printability and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If fine silver particles with internal voids are used to enable low-temperature firing, then low-temperature firing capability is improved, but surface irregularities and agglomeration occur worsening printability and conductivity
Solution Approach 1:
The surface smoothing process is divided into multiple sequential stages: first surface smoothing step, fine powder removal step, and second surface smoothing step. Each stage addresses specific surface irregularities at different levels, with the intermediate fine powder removal preventing agglomeration and enabling progressively smoother surfaces while preserving internal voids for low-temperature firing
Solution Approach 2:
Fine powder generated during the first surface smoothing step is removed in the fine powder removal step using classification equipment. This extraction of harmful fine powder prevents it from causing agglomeration and surface irregularities in subsequent processing, while the internal voids of the silver particles are preserved
2Manufacturing precision
If mechanical collision is used to smooth particle surfaces, then surface roughness is reduced improving printability, but particle aggregation occurs worsening dispersion
Solution Approach 1:
The process alternates between mechanical collision phases (surface smoothing steps) and dispersion phases (fine powder removal step with high-pressure airflow). This periodic alternation allows surface smoothing to occur while periodically removing fine powder that would otherwise cause agglomeration, maintaining both smooth surfaces and good particle dispersion
Solution Approach 2:
High-pressure airflow acts as an intermediary in the fine powder removal step, carrying away fine powder generated during mechanical collision without directly contacting the silver particles. This mediates the removal of harmful fine powder while preserving the smoothed particle surfaces and preventing aggregation
3Ease of operation
If multiple surface smoothing steps are implemented to achieve ultra-smooth surfaces, then printability is improved, but production complexity increases
Solution Approach 1:
The same type of mechanical collision equipment is used for both surface smoothing steps, and the fine powder removal step uses standard classification equipment. This multi-functionality approach achieves ultra-smooth surfaces (Ra ≤ 3 nm) through a systematic process rather than requiring specialized equipment for each step, managing complexity through standardized components
Solution Approach 2:
The process controls surface roughness by adjusting parameters such as collision intensity, processing time, and classification conditions in each step. By systematically varying these parameters across the three steps, ultra-smooth surfaces are achieved while managing process complexity through parameter optimization rather than equipment complexity
4Device complexity
If fine powder is not removed between smoothing steps, then process simplicity is maintained, but agglomeration occurs worsening conductivity
Solution Approach 1:
The fine powder generated during the first surface smoothing step, which would normally be considered waste or harmful, is systematically removed in the fine powder removal step. This converts a potentially harmful byproduct into a controlled process step that prevents agglomeration and ensures good electrical conductivity in the final product
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 silver powders with surfaces having an arithmetic average roughness of 3 nm or less, enabling conductive pastes that maintain high electrical conductivity and low susceptibility to wire disconnection even at low temperatures and during thin wire formation.
Implementation Method 1
a first surface smoothing step of causing fine silver particles having internal voids to mechanically collide with one another
Implementation Method 2
causing fine silver particles to mechanically collide with one another
Implementation Method 3
a fine powder removal step of dispersing fine silver particles present after the first surface smoothing step using high-pressure airflow while removing fine powder
Data Source
AI summary
Provided are a silver powder and a method of producing the same. The method of producing the silver powder includes a first surface smoothing step of causing fine silver particles having internal voids to mechanically collide with one another; a fine powder removal step of dispersing fine silver particles present after the first surface smoothing step using high-pressure airflow while removing fine powder; and a second surface smoothing step of causing fine silver particles present after the fine powder removal step to mechanically collide with one another.