Metal Powder for Conductive Paste via Fluidized Bed

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Solution Overview

Problem

Conventional methods for producing flaky metal powders for conductive fillers, such as ball mills and bead mills, are limited in reducing particle size, result in high voids in conductors, increased process complexity, and higher costs due to the need for drying steps and separation of crushing media.

Innovation Solution

A metal powder with an average particle diameter of not greater than 5 μm and an X value of not greater than 0.5, produced using a dry opposed jet mill, which reduces voids in conductors by forming wart-like projections on the particle surfaces, enhancing conductivity and reducing production costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If conventional mechanical crushing means (ball mill, bead mill) is used to produce flaky metal powder, then the metal powder can be obtained, but the process load is high and many voids occur in the fired conductor

Engineering Contradiction:

Improveprocess loadVSAvoidvoids in fired conductor

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent replaces conventional mechanical crushing systems (ball mill, bead mill) with a fluidized bed processing system. Metal powder particles are fluidized using upward gas flow, and flaky particles are generated through controlled collision and friction between particles in the fluidized state, eliminating the need for heavy mechanical crushing equipment and reducing process load while improving conductor quality

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the processing parameters by controlling gas flow rate, particle size distribution, and residence time in the fluidized bed to optimize the formation of flaky particles with appropriate aspect ratios, achieving low void content in fired conductors without high process load

Inventive Principle:

Principle #35Parameter changes

2Shape

If ball mill or bead mill is used for flattening metal powder, then flaky shape is achieved, but additional dry processes (drying step) are required which increases cost

Engineering Contradiction:

Improveflaky shapeVSAvoidproduction cost

Core Design Contradiction:

ShapeVSEase of manufacture

Solution Approach 1:

The patent replaces wet mechanical flattening processes with dry fluidized bed processing, where gas flow fluidizes the metal powder and particle collisions naturally produce flaky shapes. This eliminates the need for drying steps and reduces production costs while achieving the desired flaky morphology

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The fluidized bed system allows particles to self-flake through mutual collision and friction in the fluidized state, eliminating the need for external mechanical intervention and subsequent drying processes, thereby reducing production costs

Inventive Principle:

Principle #25Self-service

3Shape

If conventional crushing media (balls, beads) are used, then metal powder can be flattened, but separation process between crushing medium and material powder is required

Engineering Contradiction:

Improveflattened particlesVSAvoidseparation process

Core Design Contradiction:

ShapeVSDevice complexity

Solution Approach 1:

The patent extracts and eliminates the crushing media (balls, beads) from the system entirely, using only gas flow to fluidize and process the metal powder. This removes the need for separation processes between crushing medium and material powder, simplifying the overall device and process

Inventive Principle:

Principle #2Taking out (Extraction)

4Ease of manufacture

If metal powder is used with larger particle size, then production is easier, but conductor density is lower due to more voids

Engineering Contradiction:

Improveproduction easeVSAvoidconductor density

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent changes the particle size parameter by producing fine flaky metal powder with controlled size distribution (D50: 1-5 μm) through fluidized bed processing, achieving high conductor density while maintaining production ease through the simplified dry processing method

Inventive Principle:

Principle #35Parameter changes

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 metal powder significantly reduces voids in fired conductors, increasing density and reliability, while simplifying the production process and lowering costs, enabling finer wiring pitches and improved electronic device performance.

Implementation Method 1

when a metal powder of a specific structure flaked using a dry opposed jet mill is used as an electrically conductive filler

Methodology Applied

Scientific EffectImpact force: Impact Force

Implementation Method 2

The metal powder of this invention markedly reduces voids present in the conductor after firing

Methodology Applied

Scientific EffectMechanical deformation: Deformation

Data Source

PatentUS7618475B2Metal powder for electrically conductive paste and electrically conductive paste

Publication Date: 2009.11.17 DOWA ELECTRONICS MATERIALS CO LTD

AI summary

A metal powder for a conductive paste has an average particle diameter D50 not greater than 5 μm and an X value defined by equation (1) not greater than 0.5:X value=D50 (μm)/BET specific surface area (m2/g) (1)The metal powder for a conductive paste is particularly preferable when wart-like projections of a diameter not greater than 150 nm are present on the particle surfaces. Typical types of the metal powder include Cu, Ag, Au, Pd, Pt, Ni, Al and alloys thereof. The metal powder for a conductive paste enables fabrication of a conductor having a low void ratio after the paste is fired.