Connecting the World: Using Gold in the Electronics Industry

Consumers' seemingly unfailing appetite for ever lighter, faster and technically enhanced electronic consumer goods has been fuelling a steadily-rising demand for gold from manufacturers. An essential material in many electronic devices like laptops, iPods and cell phones, gold's immunity to environmental effects means that the technical performance of the metal remains essentially unchanged by time. Where the voltages are small, the operating conditions arduous, the circuitry complex, or reliability must be high; gold is usually the preferred material choice. According to precious metals consultancy firm GFMS, during 2007 311 tons of gold found its way into electronics devices, more gold than that used in all U.S. jewelry purchases in the same year. This article takes a current look at this important application of gold.

The Applications

Gold-plated contacts and connectors are probably the most obvious and visual use of gold by the electronics industry. As an example, a quick examination of a cell phone will almost certainly reveal gold-plated components around the battery and charging points. The choice of the best material for a contact or a connector is complex, and compromises are usually needed, but gold is generally considered the best material for low-voltage, low-current and low-contact-force applications. When two gold surfaces are brought together into intimate contact, the resulting electrical connection offers unrivalled low resistance and stability. To minimize cost, the thickness of gold used is always the minimum compatible with the performance required and this will depend on the operating conditions. Connectors for use in clean, ambient environments may require as little as 0.1 micron of gold.

Courtesy of World Gold Council www.gold.org The second large application for gold in electronics is for bonding wire, which consumes more than 100 tons of gold each year. Wire bonding is the method used to form electrical connections within a semiconductor device. Gold remains the foremost material for this application. Using gold, automated systems can achieve bonding rates of the order of 20 bonds per second. Gold's preeminence in this application is due to the very high reliability of the bonds, high production rate, and the inertness of the gold wires, ensuring that they do not corrode during the life of the chip. According to U.S. bonding wire manufacturer Kulicke and Soffa, the overall benefits of gold wire bonding make it the preferred material in more than 80% of all semiconductor devices made. As well as bonding wire and gold-plated contacts, the metal is also used in optoelectronic devices, inks for screen printing and high-melting-point solders. Taken together these uses mean gold is a fundamental commodity in the electronics industry.

What is the Cost of a Rising Gold Price?

With the gold price recently marking a record high and breaking through the $1,000/oz barrier (although currently hovering under $900), the electronics industry would like to reduce its consumption of gold, which exceeded $7 billion in 2007. For contacts and connectors the rising price has led manufacturers to consider how best they can reduce costs in gold plating. One obvious way is to seek the same performance at an even further reduced gold coating thickness. Such a strategy can have risks, however, because as the coating thickness is reduced so porosity in the coating increases, which can lead the connector to fail through corrosion of the underlying layers. Manufacturers have also been prompted to reconsider the use of a number of alternative coatings such as palladium-nickel. However, in some situations palladium coatings can catalyze the formation of insulating polymeric materials on their surfaces and can potentially lead to reliability issues.

Courtesy of World Gold Council www.gold.org In the gold bonding wire application, manufacturers of wire have met the relentless pressures to reduce cost and increase performance with aggressive product development and continuous improvement of the bonding wire process. To reduce cost, there has been a trend toward ever smaller wires diameters, with wire diameters of under 20 microns achievable. Another particularly innovative approach has been the development of an insulated wire bonding technology known as 'X-Wire' Technology, unveiled by Microbonds Inc. based in Canada. Traditionally, in order to avoid wire shorting within semiconductor devices, bare wire bonding interconnections have been largely limited to the perimeter of the chip in order to ensure that the bare wires do not touch. This uses up valuable space in the chip. By applying a proprietary coating to the wire, an insulated system can be achieved. This has obvious advantages, potentially leading to smaller, lighter chips and ultimately an improved lower cost product.

A Recyclable Metal

Courtesy of World Gold Council www.gold.org Gold is a recyclable metal. Citigroup's 2006 research report entitled "Towards Sustainable Mining" (March 2006) concluded that gold compares favorably against other commodities in terms of sustainability, in particular benefiting from its high recyclability. Now gold and the other precious metals contained in electronics products are helping to support a growing trend to recycle electronics goods at the end of their useful life. According the U.S. Environmental Protection Agency electronic waste is growing 2-3 times faster than any other waste streams. Cell phones are one of the most valuable types of this so-called 'e-waste' with each phone containing precious metals worth around a dollar, consisting mostly of gold. As a result, the presence gold has a direct impact on the level of recycling in the electronics industry. Without gold in electronic goods the economic basis for recycling would almost certainly be less robust.

Looking Ahead

It is not yet clear if future generations of electronic products will rely on the use of gold in key components, but World Gold Council, funded by the world's leading gold mining companies is seeking to ensure it remains both the material of choice in existing applications and a critical part of radical new technologies. Potential new areas of application for gold include the use of gold compounds in organic light emitting diodes and optoelectronic devices.

Courtesy of World Gold Council www.gold.org Nanotechnology also provides scope for new uses of the metal including the use of gold nanoparticles to enhance the performance of memory devices. The Council is supporting research at a number of leading research centers to accelerate the commercialization of some of these technologies as well as providing targeted funding to support feasibility studies into completely new areas of application. It has already had some success; research partner Johnson Matthey recently unveiled a patented gold nanoparticle ink that can be printed to form highly-conductive electronic circuits at room temperature.

So despite the ever present need for reduced material costs, future electronics manufacturing technologies will almost certainly demand material properties that can only be found in gold and its alloys. Without doubt gold will remain of the utmost importance to the electronics industry for many years to come.

Richard Holliday is head of Industrial Applications for the World Gold Council. More information on the uses of gold in electronics can be found at www.gold.org