Copper Nanoparticle Composition for Stable Low-Temperature Bonding
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Solution Overview
Problem
Existing metal fine particle dispersions, such as copper and silver, face challenges in achieving high bonding strength, heat resistance, and storage stability, particularly at elevated temperatures, which are essential for next-generation power devices and electronic device wiring, while also posing environmental concerns due to waste generation and electromigration issues.
Innovation Solution
A copper nanoparticle-containing composition comprising copper nanoparticles, a monocarboxylic acid with 5-12 carbons and specific functional groups, and an organic solvent, which enhances dispersion stability, low-temperature sinterability, and bonding strength, resulting in a bonded body with excellent electrical conductivity and heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If copper fine particle dispersion is used for bonding, then bonding strength can be achieved, but storage stability deteriorates due to oxidation of copper particles
Solution Approach 1:
A reducing agent is introduced as an intermediary substance to prevent copper particle oxidation during storage. The reducing agent maintains copper particles in a reduced state, acting as a protective mediator between the copper particles and oxidizing environment, thereby preserving both bonding strength and storage stability
Solution Approach 2:
The patent creates a chemically inert environment within the dispersion medium by incorporating a reducing agent, effectively establishing a protective atmosphere that prevents oxidation reactions. This inert environment allows copper particles to be stored without degrading, maintaining their bonding capabilities over time
2Reliability
If copper particles are used instead of silver, then cost is reduced and heat resistance is improved, but oxidation resistance deteriorates
Solution Approach 1:
The reducing agent serves as a protective intermediary that shields copper particles from oxidation. By introducing this intermediary substance, the patent enables copper to exhibit its superior heat resistance while compensating for its poor oxidation resistance through the mediating protective action of the reducing agent
Solution Approach 2:
The patent converts the potential harm of copper oxidation into a benefit by using the reducing agent to actively prevent oxidation. The reducing agent transforms the inherently vulnerable copper particles into a stable, oxidation-resistant system, allowing copper's advantageous heat resistance to be fully utilized
3Ease of manufacture
If lead-free solders are used for bonding power devices, then ease of manufacture is improved, but heat resistance deteriorates
Solution Approach 1:
The patent changes the material parameters from conventional lead-free solder to copper nanoparticle dispersion with specific characteristics (particle size, reducing agent content, dispersion medium composition). This parameter change enables achieving both ease of manufacture through similar processing methods and superior heat resistance through the inherent properties of copper and nanoparticle sintering behavior
4Reliability
If copper nanoparticle dispersion is used for wiring, then electrical conductivity is improved, but electromigration issues worsen
Solution Approach 1:
The patent uses nanoparticle-sized copper segments instead of bulk copper wiring. The segmented nanoparticle structure, when sintered, creates a network with shorter electron paths and reduced stress accumulation, thereby improving electrical conductivity while minimizing electromigration effects through the segmented architecture
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 composition achieves high bonding strength, electrical conductivity, and heat resistance even after storage, with reduced environmental impact by minimizing waste and electromigration, suitable for bonding and wiring applications at low temperatures.
Implementation Method 1
copper has a stable oxidation state at room temperature (25°C) and thus contains a copper atom in an oxidation state. Thus, to bond objects to be bonded using a copper fine particle dispersion, a copper atom in oxidation state needs to be reduced and fired to form a continuum of copper
Implementation Method 2
copper particles constituting the copper powder have an average primary particle size of 0.03 μm or greater and 1.0 μm or less, the surface of the copper particles is coated with a fatty acid having from 6 or more and 18 or less carbons, and a crystallite size of (111) plane of the copper particles is 50 nm or less
Data Source
AI summary
The present invention relates to: a copper nanoparticle-containing composition containing copper nanoparticles A, a monocarboxylic acid B, and an organic solvent C, wherein the monocarboxylic acid B has 5 or more and 12 or less carbons, and the monocarboxylic acid B has one or more functional groups or bonds selected from the group consisting of a hydroxy group, a ketonic carbonyl group, and an ether bond; a method for producing a bonded body using the copper nanoparticle-containing composition; and a bonded body or an electronic device using the copper nanoparticle-containing composition.