September 1999

Copper Patents

Copper Applications in Innovative Technology

By Geoff Greetham

Patents must by definition be innovative if they are to be accepted by the Patent authorities and a patent granted. An individual or organization can then produce something commercially that has been difficult or impossible to achieve before the flash of inspiration that was the birth of the patent. Where better to look then for innovation than in the Copper Development Center Patent Brief publication that scours the patent literature on a regular basis and abstracts any relating to copper.

Innovations will be doing just that in future issues, and will bring to your notice the latest, and hopefully, the most interesting ones.

In order to get started, 10 of the Patent Briefs for 1998 have been looked through to give some idea of where the innovations have been and the overall reasons for them. Patent Briefs has the following headings under which all patents are classified:

  • Extractive Metallurgy - recovering copper from copper-containing materials
  • Fabrication - ways of shaping copper into useful forms
  • Melting and Casting - techniques for melting and casting of copper
  • Surface Treatment - electrodeposition of copper and surface modifications to copper
  • Joining - methods of joining copper to itself and other materials
  • Powder Metallurgy - uses of copper powder
  • Corrosion and Oxidation - techniques for preventing corrosion of copper
  • Composites - use of copper with other materials
  • Copper Compounds - new copper compounds having special properties
  • Superconductivity - use of special copper compounds as electrical conductors
  • Applications - novel uses of copper
  • Insulation - use of copper in electrical cables
  • Pollution Control - techniques for using copper to control pollution or removing copper from waste

The short explanations do not really do complete justice to what is in the sections and more will be explained in due course.

Which ones have the greatest percentage of innovations and why?

Out in front are Surface Treatment (21.5%) and Superconductivity (20%). Looking at the individual patents soon shows why this is so. Copper has a high electrical conductivity and is used in almost all electronic equipment as the material which electrically joins together all of the electronic components on what are known as printed circuit boards. These boards are made by coating an electrically insulating backing sheet with a thin layer of copper in a special pattern, which looks like maze of copper strips. The copper strips (and the backing material) have holes in them and electronic components are placed in holes and joined to the copper strips, again in specific pattern. When finished, all of the components are joined together to produce the appropriate electronic device such as a radio, TV receiver, etc.

Producing the pattern of copper strips was almost always done by a printing a pattern onto the copper layer with an acid resistant material. The copper not covered by the acid resistant material was then removed by dipping the board in an acid bath. Hence the finished maze of copper strips on its insulating backing sheet are called printed circuit boards.

Over the years these printed circuit boards have become more complex. Instead of a single layer of copper strips, multiple layers are now produced as a sandwich of copper - backing sheet - copper - backing sheet and so on. Strips from different layers are then joined together by sophisticated plating techniques. When the electronic components are fitted and joined to the appropriate copper strips they form a 3D array instead of the old single sheet 2D array. This makes for more compact circuit boards and allows miniaturization of devices.

With the rapid growth of electronics in all aspects of modern living it is not surprising that there should be significant innovation in this, and related areas, enabling more sophisticated devices to be made and manufacturing costs reduced.

When an electrical current flows through a copper wire it does not do so without having to effectively push its way through the conductor. Copper, being an excellent conductor, puts up less resistance than most materials and is used for carrying current efficiently from place to place; hence house wiring is made exclusively from copper. Energy is however used overcoming this resistance. In some electrical devices overcoming resistance generates heat, and in other light, and we use them very day. The energy used in the conductor supplying the current to the device, such as a heater or lamp unfortunately is not useful, and is wasted.

Physicists discovered that by lowering the temperature of a metallic conductor its electrical resistance could be reduced, and in some cases a temperature was reached at which the resistance was zero. In this state electricity passing through the conductor does not do any work and consequently the same current is present at both ends of the conductor. There is no loss due to working against a resistance. The conductor has become what is known as a superconductor. The implications of this are enormous. It means that electrical current could be carried from place to place without any energy loss. Imagine how much energy would be saved in transporting electricity around the country.

Unfortunately there is a problem. The temperature at which the superconductivity was first detected was at the temperature of liquid helium, 4� Kelvin, (- 269� Celsius), just above absolute zero. Producing such a low temperature is difficult, and maintaining it indefinitely presents huge technological problems. As there isn't much helium in the atmosphere it is also expensive to produce. On the positive side though, the first superconductors were metallic and could be produced in wire form with the correct technology. They are used today for producing large electromagnets for industrial and medial purposes, the most well known being the nuclear magnetic resonance full body scanners.

A significant change in outlook took place in about 1986 when it was discovered that certain copper containing compounds could be superconducting at much higher temperatures. The superconducting temperature is now such that liquid nitrogen can be used to keep the superconductor cool. Nitrogen is abundant in the earth's atmosphere and liquid nitrogen is easy to produce. It is also much easier technologically to keep the conductor at liquid nitrogen temperature, 77° Kelvin (-196° Celsius). As time has gone on the temperature of superconductivity has slowly increased and the highest temperature is now 134° Kelvin, (- 139° Celsius). Many innovations are related to the discovery of new compounds that achieving this improvement.

Unfortunately there is still a problem. The copper compounds are not easily produced in wire form, and certainly not in sufficiently long lengths for practical purposes. Many innovations are therefore devoted to methods for making wire and tape production easier, and cheaper. Innovations will no doubt feature one or two of these in future issues.

Next in the list is Applications with 12.5%. This is a mixture of ways of using copper to advantage and cannot be summarized simply. The diverse applications covered are important and examples will arise in future issues of Innovations.

Copper Compounds (8.5%) and Composites (8.5%) fill the third place.

All the other copper compounds, excluding the superconducting ones, are included here. Again, there is no major theme as the usage, but an important series of compounds are those that react to light to generate electricity, the so-called photovoltaic materials, used to produce solar cells. More of those in a later issue of Innovations.

Composites are really combinations of copper and another material which together form a new material of product to do something novel. The good electrical conductivity of the copper is usually the contribution it makes to the composite.

After these there are the areas that have less than 4% each. Why is this so?

Take, for instance Corrosion and Oxidation with 2%. There are no great problems with corrosion of copper in the majority of its day-to-day uses; hence there is little incentive to innovate to prevent it. In fact, the corrosion products of copper and its alloys are pleasant to look at. Copper roofing has an aesthetic coloring, or patina, which occurs with age. Bronze sculptures gain a rich coloring with age that is sought after. Innovations are more likely to be methods to improve or accelerate these processes, rather than to prevent them.

Extractive Metallurgy and Fabrication each have 3.5%, reflecting the fact that the copper producing and fabrication industries are mature and well established. Copper is very amenable to being fabricated either as a pure metal or when combined with other metals to form alloys such as brass and bronze. Brass, that is, copper alloyed with zinc, is probably one of the most widely used series of alloys with too many good properties to be related here, hence there are few innovations necessary.

Powder Metallurgy is an important, and growing technology and has attracted 3% of all inventions. Copper and copper alloy powders are used for a variety of applications. Protective coatings may be applied by spraying to give an external surface with the necessary properties whilst the backing material may be cheaper and used, say, for its strength.

Another important example of the use of powders is in the production of components very close to their finally required shape. In this technique metal powders are put into containers and pressed to make all of the metal particles interlock together. At this stage the pressed powder compact is handleable but has very little mechanical strength. After removal from the container the compacted powder is subjected to a high temperature heat treatment, (sintering), that makes each powder particle diffuse into its neighbors. In this way a strong bond is formed and a useful component produced. The reason for going to all this trouble is simply that there is less waste material, as the component does not normally require machining operations to finish it. It is therefore an environmentally friendly process. This is coupled with an ability to mix other constituents into the metal powder so that they are incorporated into the final component. In many cases this is the only way of producing such materials that can have very special properties. One well-known use of powder metallurgy is the production of automotive brake pads using copper powder as the major constituent. The copper acts as a heat conductor and also allows other materials to be incorporated into it, such as aluminum oxide and graphite that control the friction properties of the finished product and provide a useable and cost-effective brake pad.

Pollution Control at 2.5% should be noted for the methods to remove copper (and other metals) from waste products. However, copper is a good bactericide, a fact known to wine growers for many years. A combination of lime, copper sulphate and water, called Bordeaux Mixture, has been used to keep vines healthy and prevent disease since the 1880s. Further back in history, the English built copper-bottomed ships that kept clean, so increasing the speed of the sailing ships. Wooden boats with barnacles on them were slower and so could be outmaneuvered. In more recent times Florida fishing boats with hulls clad with a copper-nickel alloy have kept free from crustaceans, This has removed the need to spend time in dry dock having the hull cleaned, and also significantly improved fuel efficiency.

This use of copper in solution has been used in one innovative process to provide bacterial control in recirculating water systems, more of which will be explained in the future.

And so it is possible to see why there are innovations relating to copper and what areas these innovations will probably be in. They will tend to exploit the excellent electrical properties of copper, the corrosion resistance of its alloys, the ability to electroplate easily, the unusual properties of copper compounds, its bactericide effects, and the advantageous results of combining copper with other materials in composites and powder metallurgy.

Perhaps this is now enough to whet your appetite to know more about some of the innovations over the past year, and if so they will be found in future articles in Innovations.

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