Nanoparticle Paste Formulation for Crack-Free Consolidation
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Solution Overview
Problem
Current lead-free solder alternatives, such as the Sn/Ag/Cu system, face challenges in extreme environments due to high eutectic melting points, cost issues with silver, and tin whisker formation, while metal nanoparticles are prone to clumping and cracking during consolidation, making them unsuitable for precision applications like screen and ink-jet printing.
Innovation Solution
A nanoparticle paste formulation is developed, containing metal nanoparticles dispersed in an organic matrix with a tailored solvent composition of hydrocarbons, alcohols, amines, and organic acids, which promotes dispensability and reduces cracking and void formation during consolidation by maintaining high solids content and using a slow heating profile with temperature plateaus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If metal nanoparticles are used as solder material, then processing temperature can be reduced to levels comparable to traditional lead-based solder, but the nanoparticles are prone to clumping and cracking during consolidation
Solution Approach 1:
The patent introduces an organic matrix as an intermediary medium to disperse metal nanoparticles during processing. This matrix prevents direct nanoparticle-nanoparticle contact that causes clumping, while allowing controlled consolidation when the matrix is removed through heating, thus resolving the contradiction between low-temperature processing and consolidation quality
Solution Approach 2:
The patent changes the physical and chemical parameters of the nanoparticle system by embedding them in an organic matrix with specific viscosity and compositional characteristics. This parameter modification enables the nanoparticles to maintain dispersion at low temperatures while facilitating crack-free consolidation during the controlled removal of the matrix
2Quantity of substance
If as-produced metal nanoparticles are used directly, then material purity is maintained, but they are difficult to dispense and consolidate without clumping
Solution Approach 1:
The organic matrix serves as a mediator that enables dispensing of high-concentration nanoparticle formulations. The matrix provides fluidity and flow characteristics necessary for dispensing operations while maintaining the high nanoparticle concentration required for effective consolidation, resolving the contradiction between material purity/concentration and ease of operation
3Productivity
If rapid heating is used to consolidate nanoparticles, then processing time is reduced, but cracking and void formation increase
Solution Approach 1:
The patent implements preliminary action by first removing the organic matrix through controlled heating before complete nanoparticle consolidation. This staged approach prevents rapid volume contraction that causes cracking, while still maintaining relatively high productivity through the use of temperature plateaus and optimized heating rates
Solution Approach 2:
The consolidation process uses periodic action through temperature plateaus where the heating rate is temporarily reduced or halted at specific temperature ranges. This periodic heating pattern allows controlled removal of the organic matrix and prevents defect formation while maintaining overall processing efficiency
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 nanoparticle paste formulation enables efficient consolidation of metal nanoparticles with reduced cracking and void formation, maintaining mechanical strength and electrical conductivity, and is suitable for precision applications like electronics manufacturing and soldering.
Implementation Method 1
nanoparticle paste formulations containing an organic matrix and a plurality of metal nanoparticles dispersed in the organic matrix
Implementation Method 2
the as-produced metal nanoparticles are often prone to clumping and are difficult to directly use
Implementation Method 3
cracking and void formation can occur due to volume contraction as the solvent and surfactant are removed from the vicinity of the metal nanoparticles
Implementation Method 4
cracking and void formation can occur due to volume contraction as the solvent and surfactant are removed
Implementation Method 5
metal nanoparticles to be at least partially consolidated into bulk objects
Implementation Method 6
at least partially consolidated into bulk objects, joints, and coatings
Data Source
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AI summary
Nanoparticle paste formulations can be configured to maintain a fluid state, promote dispensation, and mitigate crack formation during nanoparticle fusion. Such nanoparticle paste formulations can contain an organic matrix and a plurality of metal nanoparticles dispersed in the organic matrix, where the plurality of metal nanoparticles constitute about 30% to about 90% of the nanoparticle paste formulation by weight. The nanoparticle paste formulations can maintain a fluid state and be dispensable through a micron-size aperture. The organic matrix can contain one or more organic solvents, such as the combination of one or more hydrocarbons, one or more alcohols, one or more amines, and one or more organic acids. Optionally, the nanoparticle paste formulations can contain about 0.01 to about 15 percent by weight micron-scale metal particles or other additives.