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Nanotape may soon replace solder pads

Posted: 26 Jan 2011 ?? ?Print Version ?Bookmark and Share

Keywords:nanotape? solder pads? thermally conductive carbon nanotubes?

A new nanotape material jointly developed by the Semiconductor Research Corp. (SRC) and Stanford University could soon drive solder pads to obsolescence.

Researchers claim that nanotape takes heat away from chips better than solder by squeezing in thermally conductive carbon nanotubes between thin metal foils. Furthermore, it uses a lightweight, flexible material that is both cheaper and more compliant.

"Today, solder is made very thick to provide mechanical compliance, but our nanotape can replace those solder pads with a thin lightweight material that improves thermal energy management," said professor Ken Goodson, lead researcher for SRC at Stanford University. "Our tape consists of a vertically aligned carbon nanotube forest at its central core, with carefully chosen alloys on both the top and bottom that wet the carbon nanotubes, and also will contact to the heat sink and the chip."

To the unaided eye, the nanotape will look like a conventional solder pad, because both the top and bottom are metallic. But inside it will harbor the superior thermal conduction of the carbon nanotubes.

"The nanotape will look like a conventional solder pad, and will work well in the same equipment, but it has the mechanical characteristics of an aerogel and the thermal conductivity of a metal," said Goodson.

Initially the material, which has a thermal conductivity comparable to copper, will be fabricated as a direct replacement for solder pads, according to SRC. However, its foam-like flexible compliance, which allows it to shrink and expand in concert with semiconductors in a manner impossible for solder, could form the basis for entirely new semiconductor packaging techniques.

Early adopters of nanotape will likely be graphic-accelerator and gaming semiconductors, which today must grapple with hot spots on their chips that limit their performance. Using nanotape, however, will better cool hot spots by remaining compliant to the semiconductors as they expand and contract during heating.

"Nanotape will cool hot spots better, removing a current roadblock to increasing chip performance," said Goodson.

Besides semiconductors, Stanford is also working with the National Science Foundation on a project with the Department of Energy Partnership on Thermoelectric Devices for Vehicle Applications. Here, the nanotape will facilitate the recovery of electrical power from hot exhaust gases using thermoelectric energy converters. According to Goodson, nanotape can more reliably transfer heat to thermoelectric generators, enabling greatly improved fuel economy.

The researchers predict that early adopters will start using the nanotape by the end of next year, with mainstream benefits to end users commencing circa 2014. The SRC-funded nanotape material will be made available to all SRC members, which include Advanced Micro Devices, Applied Materials, Axcelis Technologies, Cadence Design Systems, Freescale Semiconductor, Hewlett-Packard, IBM, Intel, LSI Corporation, Mentor Graphics, Novellus Systems, Rohm and Haas Electronic Materials, Texas Instruments and Tokyo Electron.

- R. Colin Johnson
EE Times

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