Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers design copper connections for high-speed computing

14.02.2008
Connections fabricated between computer chips, external circuitry and processors

As computers become more complex, the demand increases for more connections between computer chips and external circuitry such as a motherboard or wireless card. And as the integrated circuits become more advanced, maximizing their performance requires better connections that operate at higher frequencies with less loss.

Improving these two types of connections will increase the amount and speed of information that can be sent throughout a computer, according to Paul Kohl, Thomas L. Gossage chair and Regents’ professor in Georgia Tech’s School of Chemical and Biomolecular Engineering. Kohl presented his work in these areas at the Materials Research Society fall meeting.

The vertical connections between chips and boards are currently formed by melting tin solder between the two pieces and adding glue to hold everything together. Kohl’s research shows that replacing the solder ball connections with copper pillars creates stronger connections and the ability to create more connections.

“Circuitry and computer chips are made with copper lines on them, so we thought we should make the connection between the two with copper also,” said Kohl.

Solder and copper can both tolerate misalignment between two pieces being connected, according to Kohl, but copper is more conductive and creates a stronger bond.

With funding from the Semiconductor Research Corporation (SRC), Kohl and graduate student Tyler Osborn have developed a novel fabrication method to create all-copper connections between computer chips and external circuitry.

The researchers first electroplate a bump of copper onto the surface of both pieces, a process that uses electrical current to coat an electrically conductive object with metal. Then, a solid copper connection between the two bumps is formed by electroless plating, which involves several simultaneous reactions that occur in an aqueous solution without the use of external electrical current.

Since the pillar, which is the same thickness as a dollar bill, is fragile at room temperature, the researchers anneal it, or heat it in an oven for an hour to remove defects and generate a strong solid copper piece. Osborn found that strong bonds were formed at an annealing temperature of 180 degrees Celsius. He has also been investigating how misalignments between the two copper bumps affect pillar strength.

“I’ve also studied the optimal shape for the connections so that they’re flexible and mechanically reliable, yet still have good electrical properties so that we can transmit these high frequency signals without noise,” said Osborn.

The researchers have been working with Texas Instruments, Intel and Applied Materials to perfect and test their technology. Jim Meindl, director of Georgia Tech’s Microelectronics Research Center and professor in the School of Electrical and Computer Engineering, and Sue Ann Allen, professor in the School of Chemical and Biomolecular Engineering, have also collaborated on the work.

In addition to this new method for making vertical connections between chips and external circuitry, Kohl is also developing an improved signal transmission line with the help of graduate student Todd Spencer.

“Several very long communication pathways exist inside a computer that require a very high performance electrical line that can transmit at higher frequencies over long distances,” explained Spencer.

This is especially important in high-performance servers and routers where inter-chip distances can be large and signal strength may be significantly degraded. Kohl and Spencer have developed a new way to link high-speed signals between chips using an organic substrate, with funding from the Interconnect Focus Center, one of the Semiconductor Research Corporation/Defense Advanced Research Projects Agency (DARPA) Focus Center Research Programs.

Fabrication begins with an epoxy fiberglass substrate with copper lines on one side. The substrate is coated with a polymer and the areas without copper lines are exposed to ultraviolet (UV) light, which disintegrates the polymer where it’s not wanted. Then, the researchers coat the substrate with another polymer that hardens when exposed to UV light. Layers of titanium and copper are added on top of each copper line. When the layered substrate is heated at 180 degrees Celsius, the first polymer layer decomposes into carbon dioxide and acetone, which diffuse out leaving an air pocket.

“The amount of electrical loss relates to the connection’s sensitivity at higher frequencies,” explained Spencer. “Just having this air pocket there reduces our signal loss greatly.”

The researchers are currently designing a coaxial cable for this chip-to-chip signal link, which should greatly increase the maximum signal frequency the connection can carry.

Companies that make computer chips and package them into a device are very interested in these technologies, said Kohl.

“If these connections can be produced at a reasonable cost, they could be very important in the future because you’re giving the customer a better product for the same cost,” said Kohl.

Abby Vogel | EurekAlert!
Further information:
http://www.gatech.edu

More articles from Information Technology:

nachricht New epidemic management system combats monkeypox outbreak in Nigeria
15.12.2017 | Helmholtz-Zentrum für Infektionsforschung

nachricht Gecko adhesion technology moves closer to industrial uses
13.12.2017 | Georgia Institute of Technology

All articles from Information Technology >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First-of-its-kind chemical oscillator offers new level of molecular control

DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.

Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Engineers program tiny robots to move, think like insects

15.12.2017 | Power and Electrical Engineering

One in 5 materials chemistry papers may be wrong, study suggests

15.12.2017 | Materials Sciences

New antbird species discovered in Peru by LSU ornithologists

15.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>