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Oxidation-proof copper could replace gold, meaning cheaper chips, says prof

One hopes this won't hike the price of Cu

Scientists claim to have found a way to stop copper from oxidizing. If they're right, this could potentially allow copper to replace gold in electronics, leading to lower costs and, ultimately, cheaper components.

The academics at Pusan National University in South Korea say they have developed a method to fabricate atomically flat single-crystal copper thin films, and that this offers semi-permanent resistance to oxidation. The boffins developed this method along with colleagues at Sungkyunkwan University, also in Korea, and Mississippi State University in the US, and the research behind it is described in a paper published in Nature.

Copper is used pretty much universally in electronics because of its excellent electrical conductivity, from wiring to the tracks on circuit boards. But oxidation and corrosion on its surface can lead to increased electrical resistance and limit the lifespan of components in some cases. For this reason, gold is often used in key areas – such as coating connectors and in the bonding wires used to connect a silicon die to the pins that form external connections.

According to Professor Se-Young Jeong, who led the Pusan University team, replacing this gold with copper could reduce costs in the electronics industry.

"Oxidation-resistant Cu (copper) could potentially replace gold in semiconductor devices, which would help bring down their costs. Oxidation-resistant Cu could also reduce electrical consumption, as well as increase the lifespan of devices with nanocircuitry," according to the professor in a statement.

The research team observed that previous studies had found that oxidation occurs due to microscopic "steps" on the surface of the copper, which provide a source of adsorbed copper atoms that interact with oxygen and provide a starting place for oxides to grow. The team started from the hypothesis that oxidation resistance would require surface step edges to be avoided.

To realize this, the Pusan team used a method called atomic sputtering epitaxy to grow flat, single-crystal copper films. According to Prof Jeong, they were able to keep the copper surfaces almost entirely defect-free and fabricate atomically flat films.

When they compared their single-crystal copper with other copper surfaces, they found it had an almost entirely flat surface with only occasional mono-atomic steps that were much more resistant to oxidation because it was difficult for oxygen to penetrate the mono-atomic step edge.

But would replacing gold with copper really save much on costs? Looking at recent daily spot prices for metals might suggest so. Copper comes in at around $10k per metric tonne, while gold is over $62m per metric tonne – quite some difference. By some estimates, about 66.4 tonnes of gold was used in electronic components last year – which is likely to be much lower than the figure for copper.

Unless the oxidation-resistant copper can be produced commercially, this is no more than an academic exercise. We asked Pusan National University if it planned to commercialize the process, or license it to a third party, and we will update this article if we receive a response.

There is also the matter of the copper supply itself. According to Rystad Energy, an energy research and business intelligence outfit, global demand for copper is likely to outstrip supply by more than six million tonnes by 2030.

Rystad Energy believes that annual demand for copper will have risen by 16 percent by the end of the decade, to 25.5 million tonnes. Meanwhile, supplies are forecast to decrease by 12 percent versus 2021 levels, to 19.1 million tonnes. It said that significant new investment in copper mining would be required to avoid the shortfall.

The laws of supply and demand would suggest that the above scenario will put upward pressure on copper prices, dulling somewhat the price advantage of replacing gold. ®

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