Custom Silver Dispersions
Five Star Technologies offers a complete line of custom silver dispersions, allowing users of
silver to eliminate unnecessary process steps and enabling new performance profiles in formulated
silver products. Five Star silver dispersions are custom formulated to meet a wide range of customer
needs, with chemistries available to stabilize silver powders, flakes or nano-particles in a range of
media. All Five Star silver dispersions are characterized by narrow particle size distributions
targeted at the low micron or nano range. Excellent top size control is achieved, allowing use in
tight tolerance applications. Increased surface areas and high tap densities are inherent in all systems.
An example of a silver dispersion in water is shown in the SEM images below. The input material
shown on the top is typical of many silver powders, being highly agglomerated in large clusters of
particles. The Five Star dispersion provides a fine uniform particle distribution with excellent
top size control that eliminates the need for expensive paste production processes such as three-roll
or horizontal bead milling. The ability to formulate inks and pastes that allow creation of finer
features can eliminate subtractive processes related to circuit element construction.
In addition, Five Star has demonstrated the ability to stabilize nano-silver particles synthesized
for more demanding applications. The chart below presents particle size distributions for a
custom nano-silver dispersion in solvent produced by Five Star. Although the material as synthesized
has a particle size in the tens of nanometers, it is so aggregated that its mean particle size as
received was 14 microns, with many aggregates larger than 42 microns. As shown, Five Star formulated a
dispersion in the customer’s target solvent medium with a D50 of 190 nm. Top size was controlled to a
D90 of 360 nm, enabling the use of the material in advanced applications where extremely fine features are required.
The following table provides a representative sampling of the wide range of silver dispersions
available from Five Star. The table provides product examples for silver spheres, silver flakes
and nano-silver spheres. Five Star has worked successfully with essentially all domestic silver
producers and a global set of nano-silver suppliers. The products listed are intended to demonstrate
capability, but do not represent the bounds of our technology, as many of the particle sizes indicated
were targeted to specific customer needs. Dispersion media shown include water, organic solvents and an
epoxy resin system. The water-based dispersions can be provided as-is at concentrations of 40-50% by
weight. We will also work with you to prepare these dispersions and have them dried by the representative
silver producer and provided to you in a dry powder or flake form.
Representative solvent-based systems are also shown in the table. We have created dispersions in most
of the solvents commonly used in screen printable thick film pastes. Silver concentrations of 80% by weight
are routinely achieved; higher loadings are available in many systems.
The epoxy system listed in the table was done under confidentiality and thus we are unable to share data
other than the micrographs shown below. Our experience suggests that we can replicate the solvent/water
performance in many resin systems. We will be happy to prepare custom dispersions in the resin of your choosing.
| FST Product |
Silver |
Medium |
D10 (µm) |
D50 (µm) |
D90 (µm) |
Mean (µm) |
| X-103 |
Sphere (0.9 µm) |
Aqueous |
0.19 |
0.95 |
2.16 |
1.09 |
| X-104 |
Sphere (1.6 µm) |
Aqueous |
0.24 |
1.79 |
3.06 |
1.79 |
| X-112 |
Sphere |
Aqueous |
0.16 |
0.8 |
1.75 |
0.86 |
| X-113 |
Sphere |
Solvent |
0.74 |
1.58 |
3.37 |
1.91 |
| X-151 |
Flake |
Aqueous |
0.22 |
2.16 |
3.2 |
2.03 |
| X-152 |
Flake |
Solvent |
0.91 |
1.25 |
1.71 |
1.29 |
| X-155 |
Flake |
Aqueous |
0.34 |
2.86 |
6.82 |
3.39 |
| X-180 |
Nano (60 nm) |
Solvent |
0.10 |
0.19 |
0.36 |
0.20 |
| N/A |
Flakes |
Epoxy |
See attached micrograph |
This data illustrates Five Star’s ability to convert conventionally produced silver powders and
flakes into high-performance, submicron materials capable of meeting the electronic industry’s present
and future feature size requirements. A wide variety of solvents and carriers can be accommodated,
eliminating dispersion and milling steps for the formulator and delivering a higher performance input
material. We have the experience to design a system to meet your performance needs and look forward
to working closely with you to meet all your needs for high performance silver-based products.
Product Bulletin - Custom Silver Dispersions
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