SPI Conductive Silver Paint
More useful information
The SPI #5001-AB and #5002-AB Silver Paint
Product (the same product in two different size bottles) is a highly
concentrated suspension (43% ±3% silver solids) of specially prepared and
tightly controlled high purity silver powder combined with a highly
effective organic suspending and binder system.
The product is formulated to produce electrically conductive paths,
patterns or films over nonconductive surfaces. The product is also
designed for strictly room temperature air drying applications since for
the most part, samples being mounted for SEM can not tolerate higher
temperatures. The product is sufficiently versatile that it can be dried
at elevated temperatures as well, especially for those using the product
in UHV (e.g. ultra high vacuum) systems. More often than not, the
substrate composition dictates the limit to the possibilities for drying
(curing) temperatures.
We are often times asked about drying "rate". Of course the real question
being ask is how long does one have to wait before inserting their specimen
into the column and vacuum system of their SEM. And, like with so many
other things, there is no unambiguous answer. Drying time is a function of
the solvent system, the method of application (dictated by viscosity), and
the binder to solvent ratio.
We are also asked about the suitability of this product for application to
various types of surfaces. It can be applied to various types of organic as
well as inorganic substrates, mainly for the purpose of "painting on" a
silver conductor line that serves as a surface electrode. It furthermore is
formulated for brush or automatic bonding applications or it can be thinned
for spray application. Some typical applications outside of the the SEM
laboratory include printed circuit board repair, shielding paint,
plating base and capacitor electrode formation.
The thinner SPI #5004-AB has been formulated to give optimum results for use
with the two SPI silver paint products. Only this recommended thinner should
be used for optimum results.
Other potentially useful information about the SPI Silver Paint products,
#5001 and #5002:
%Silver Solids 43% ±3%
Viscosity1 280-400 cps
Cure temperatures 1 hour at 60°C
Typical Cured Properties2:
Sheet resistivity3
Resistivity: < 60 mohms/sq./mil
----------------------------
1 As measured by Brookfield LVT, Spindle #2, at 30 rpm, 25 °C ± 1 °C
2 Dried at 80 °C for 10 minutes then cured at 100 °C for 15 minutes
3 The value given is for "sheet" resistivity, which is a way of measuring
the ability of a layer of material, such as a layer of a paint coating,
to conduct charge away, or dissipate it, on a surface. The term is
widely used in the specification of materials for ESD protection, and
we are using it for the rather specialized use of charge dissipation
in scanning electron microscopy. The "per square" term is really
"per square centimeter per square centimeter" or "per square inch per
square inch", and the units cancel each other out, but convention is to
use the unit "per square" to remind us that area is an important
consideration. Since the larger the area of the layer of coating being
measured, the larger the cross sectional area through which the charge
is being dissipated, the "per square" term really does make sense. The
best parallel is that thermal expansion is measured in "dimensionless"
units like "centimeters per centimeter", and eventually we get used to
the idea that you can plug in any length and temperature change and get
the dimensional change in the same units in which you entered the length.
In this case, the resistivity of a layer of silver paint one mil
(0.001"/25µm) thick is less than 60 milliohms, whatever the area
of the measurement.
Processing Procedures
Mixing: This product has excellent resistance to "hard pack settling"
and is relatively easy to redisperse after long term storage. The preferred
method of remixing is by slow rolling on a jar rolling machine for several
hours before use. The material may also be shaken in a high speed paint
shaker machine for 5-10 minutes, but must be allowed to stand for some time
in order for entrapped air bubbles to escape. These two approaches are
primarily for customers of bulk silver suspension and would be overkill for
the small bottle 0.5 and 1.0
troy oz products. For the resuspension of the product in the small
bottles, a simple laboratory ultrasonic
shaker can be used for a few minutes to return the suspension to its
"ready to use" state.
Painting: The paint is ready to use as received for brush
application. It may need slight thinning after prolonged storage due to
solvent evaporation. Do not over-thin the paint. Use small portions of the
SPI recommended thinner
until the desired viscosity is obtained.
Drying: The paint was formulated to be air dried to a tack-free state
within 30 minutes. Adequate conductivity and adhesion are achieved after 24
hours in air at 25 °C. Adhesion may be improved if necessary and the
cure accelerated by force drying at 100-150 °C for 15-30 minutes.
Storage: The SPI Silver Paint should be stored in sealed containers
away from heat or flames. In the large one gallon size bottles, it has a
shelf life of 3 months at a storage temperature of 25 °C. Once in the
small glass containers, with the special brush applicator tops, however,
the heat seal is applied in a way that the shelf life can be described in
terms of years rather than months. Five years or even more can be expected
provided storage is as described above.
Disclaimer statement: SPI Supplies and Structure Probe, Inc. provide
this information in good faith and it is based upon data believed to be
reliable. However, we make no warranties, expressed or implied, as to its
accuracy and assume no reliability arising out of its use by others or any
patent infringement resulting from its use.
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