Tiny 20µm Cu-Ag Bumps Prove Easy to Manufacture, Show Potential for Next-Generation Electronics

Producible at lower temperatures and pressures than current equivalents, these tiny metal sandwiches are easier to build.

Gareth Halfacree
4 days agoHW101 / Sustainability

A team of scientists in Osaka University's Flexible 3D-System Integration Laboratory have developed a new way to bond copper electrodes using silver — which, the researchers claim, could boost the efficiency of future electronics while simultaneously lowering their cost.

"Our process can be performed under gentle conditions, at relatively low temperatures and without added pressure," first author Zheng Zhang explains of the team's work in the field of semiconductor device manufacturing, "but the bonds were able to withstand over one thousand cycles of thermal shocking from -55 to 125°C [-67 to 257°F]."

The bonds in question are designed for use in three-dimensional stacked components, where layers of silicon are placed one on top of the other in order to create more complex components without increasing the footprint and thus the distance between the furthest components.

In order to work, though, 3D chips need connections between the silicon layers — and it's these interconnects that Zhang and colleagues have developed. Dubbed "20µm Cu-Ag bumps" — because they're physical bumps sticking up from the surface of the silicon, made of a titanium-copper-titanium sandwich finally finished with a cap of silver, measuring 20µm in width — the interconnects are small, stable, and easier to manufacture than current approaches.

"This technology," claims senior author Katsuaki Suganuma of the interconnects developed by the team, "is expected to contribute to chips with a high density of interconnects and advanced 3D packaging."

The team's work was presented at the IEEE 72nd Electronic Components and Technology Conference (ECTC), but has not yet been released for download.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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