Copper Powders for Conductive Ink
Copper powder may be used to make conductive
inks and conductive paints, but how do you know which copper powder is the right
product for electrical conductivity?
(This article is about the electrical
conductivity of copper powder. If you need copper powder to make heat conductive
compounds, this article does not apply to you. Please read "Copper
Powders for Heat Conductivity" or call us for assistance.)
How to select the right copper powder for
When choosing copper powder for electrical
conductivity, you must immediately eliminate powders that have spongy,
spherical or irregular particles. Such powders do not offer sufficient contact surface where
particles touch each other. This can cause a lot of resistance and reduce
the electrical conductivity of your products. For conductivity applications only
select copper powders with flat particles. This will allow a large surface
contact and high conductivity or low resistance to you conductive compound.
Copper powder grades
and CU5005F are among copper powders with flat particles.
|Another factor is the purity of copper
powder. Always look for powders with purity of 97% or higher. When
making copper powder for conductivity, small amounts of mineral oil is
added to the powder in order to prevent oxidation. Without a protective
oil, copper oxides, carbonates and other salts may form on the surface
and reduce the conductivity. Mineral oils protect the surface of copper
particles against oxygen and corrosive gases found in the air.
In addition to a better conductivity, flat
particles offer a metallic shine that makes them the pigment of choice for
makers of conductive paints and conductive inks.
|Metallic copper pigments are very
durable because they are naturally resistant to UV light and they are
biostatic. In other words fungus, bacteria and other forms of micro
organisms cannot grow or propagate in presence of copper. That is why
copper powders are added to marine paints to prevent biofouling.
Copper is not the only component of
conductive inks or conductive paints. A binding agent, resin or carrier
is needed as well.
How to select the right binding agent for
|Although copper is one of the best
known conductive metals and most electrical wires are made of copper, it
will not show any conductivity when it is in the form of powder. This
often comes as a surprise for those who are trying to make a conductive
ink or conductive paint using copper powder. The reason that copper
powder does not show any conductivity is the loose contact between
particles, oxides on the surface and low voltage used to test
Copper Powder for Conductive Ink
As soon as you add a few drops of water
or oil to the copper powder it passes the conductivity test. This however does
not mean that you can use any resin or binder to make conductive ink or paint.
Most resins and binders work as insulators and when mixed with copper powder,
the result will not be conductive.
Conductive binders or resins are commercially
available and many methods of producing them are patented. This however does not
mean that you cannot research and find your own concoction. Any chemist can do
that and come up with a practical recipe in a few weeks. In just a few hours I
tried a number of water soluble binders and they all gave some positive result.
I tried gum Arabic, guar cum, acrylic paint, sodium silicate and
polyvinyl alcohol (PVOH 50-42). I did use other additives to increase ionization
and I also used hydrochloric acid in the compound or as a surface cleaner after
the ink is dried.
Questions? Please call
973-405-6249 to discuss your specific needs.