A Nanosolution Eliminates the Danger of
Tiny Tin Whiskers
Tiny Tin Whiskers
In the manufacturing world, unintended consequences can impact cost, schedule and performance. For example, several years ago, manufacturers set out to rid electronics of hazardous materials by removing lead from solder. Unfortunately, the tin-based, lead-free solder became prone to a detrimental phenomenon known as tin whiskers, microscopic metal growths on soldering points of a circuit board that often lead to short circuits.
In an era of growing electronics dependence, tiny tin whiskers pose a global problem. And, in a moment of innovation, Lockheed Martin materials scientist Dr. Alfred Zinn found a nanoscale solution.
It all began with a team at Lockheed Martin’s Advanced Technology Center in Palo Alto, Calif., working on a project to reduce the processing temperature of rhenium metal – a material very desirable for its high melting point and temperature corrosion resistance, but difficult to process for the same reasons.
Innovation is more than a technical invention. Innovation can also be solving a challenge by thinking of new ways to apply existing technology. In this case, using the company’s nanotechnology development efforts already under way, Dr. Zinn was able to create rhenium metal nanoparticles, which reduced its processing temperature by 80 percent.
It was then that he thought to answer the call for lead-free solder in what he calls CuantumFuse™, a printable nanocopper paste. Dr. Zinn found that he needed copper nanoparticles in the sub-10 nanometer range to achieve a fusion or melting point temperature around 200 degrees Celsius, the desired processing temperature for electronic assembly.
This is an amazing feat considering that the melting point of a metal-like copper is a physical constant at 1,083.4 degrees Celsius. In other words, copper does not melt below this well established temperature.
Improving Performance and Reliability
“In a sense, we were able to trick Mother Nature without violating the laws of physics,” said Dr. Zinn. “It is amazing that we can now employ nanotechnology and break fundamental boundaries that we previously thought to be ‘physical constants.’ Now, we are able to take a material with a given melting point and lower its processing temperature by 80 percent or more thereby accessing application space once thought to be impossible, such as using copper to replace solder.”
Since solder is a low cost commodity item and can only be replaced by a competitive product, Lockheed Martin created a synthesis process that allows for fast and affordable production of CuantumFuse™. Replacing tin-based solder with pure copper solder offers several benefits: much greater thermal and electrical conductivity, the elimination of the danger from whiskers and improved product performance by an order of magnitude once fully developed.
“CuantumFuse™ is a true revolution that offers high reliability and a lead-free solution for a wide variety of commercial and government applications,” said Dr. Ken Washington, vice president, Advanced Technology Center. “This innovative use of nanotechnology opens a breadth of opportunities in the automobile and medical industries, electronic cooling and others where long service life, reliability and robustness of components are critical.”
August 18, 2013
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