Featured Research

from universities, journals, and other organizations

Copper Connections Designed For Ultra High-speed Computing

Date:
February 15, 2008
Source:
Georgia Institute of Technology
Summary:
As computers become more complex, the demand increases for more connections between computer chips and external circuitry and better connections that operate at higher frequencies with less loss. Researchers are developing new methods to improve these two types of connections to increase the amount and speed of information that can be sent throughout a computer.

Scanning electron microscope image of two copper pillars bonded together using a novel fabrication technique. Placing these all-copper connections between computer chips and external circuitry will lead to increased computing speeds.
Credit: Image courtesy of Tyler Osborn

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.

Related Articles


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.


Story Source:

The above story is based on materials provided by Georgia Institute of Technology. Note: Materials may be edited for content and length.


Cite This Page:

Georgia Institute of Technology. "Copper Connections Designed For Ultra High-speed Computing." ScienceDaily. ScienceDaily, 15 February 2008. <www.sciencedaily.com/releases/2008/02/080211172547.htm>.
Georgia Institute of Technology. (2008, February 15). Copper Connections Designed For Ultra High-speed Computing. ScienceDaily. Retrieved November 24, 2014 from www.sciencedaily.com/releases/2008/02/080211172547.htm
Georgia Institute of Technology. "Copper Connections Designed For Ultra High-speed Computing." ScienceDaily. www.sciencedaily.com/releases/2008/02/080211172547.htm (accessed November 24, 2014).

Share This


More From ScienceDaily



More Computers & Math News

Monday, November 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Symantec Uncovers Sophisticated Spying Malware Regin

Symantec Uncovers Sophisticated Spying Malware Regin

Newsy (Nov. 24, 2014) A Symantec white paper reveals details about Regin, a spying malware of unusual complexity which is believed to be state-sponsored. Video provided by Newsy
Powered by NewsLook.com
Hackers Target Business Travellers

Hackers Target Business Travellers

Reuters - Business Video Online (Nov. 24, 2014) A newly detected malware, dubbed Darkhotel, infects hotel networks with spying software to steal sensitive data from the computers of high profile business executives, warns a leading computer security firm. Ciara Lee reports. Video provided by Reuters
Powered by NewsLook.com
Microsoft Adds Robot Guards, Ushers In Sci-Fi Apocalypse

Microsoft Adds Robot Guards, Ushers In Sci-Fi Apocalypse

Newsy (Nov. 23, 2014) Microsoft has robotic security guards working at its Silicon Valley Campus. Video provided by Newsy
Powered by NewsLook.com
European Parliament Might Call For Google's Break-Up

European Parliament Might Call For Google's Break-Up

Newsy (Nov. 22, 2014) This is the latest development in an antitrust investigation accusing Google of unfairly prioritizing own products and services in search results. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins