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 conductive Ink?

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 grade CU7005F is 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 conductive Ink?

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 conductivity.

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 973-405-6247 to discuss your specific needs.