Friday, May 16, 2008

Radioactivity in Lead: Arresting Our Progress in Microelectronics?

Before it’s lead’s toxic effects to the human physiology that became an issue, now it’s the potential for too much alpha-particle emission. Will lead’s role in the electronic industry ever be less controversial?

By: Vanessa Uy

The Nobel Prize winning physicist Richard P. Feynman once said that a civilization’s technical prowess is gauged on how small they can built something or something similar like this but you get the picture. As our consumer electronics industry tries to design and built even smaller chip, they may find out that there’s a price to be paid in terms of device operational reliability. And they may soon reach their limit before it is imposed by the atomic structure of the semiconductor chips they are fabricating.

As an industry that prides itself on having enough time on their hands to ponder the sexier aspects of their work, the consumer electronics industry could be interpreted as so full of it whenever they ponder deep solid-state physics questions like how quantum-mechanical effects disrupt electrons. I mean how likely does the phenomena of electroweak interaction of Steven Weinberg and Abdus Salam affect the day –to –day workings of our consumer electronic goods? Well, they – the electronic engineers involved in mass-producing consumer electronic goods - can now get their hands dirty in tackling on what used to be a theoretical problem. Namely how alpha-particle emissions from lead isotopes affect the reliability of their latest microprocessor’s operation? But before we proceed, here’s a primer on where all of this “hot lead” came from.

The much heavier elements found on the Earth’s crust were created by our Sun’s larger and much heavier predecessor; after it went out into a blaze of glory by turning into a supernova. In the briefest fractions of a second before blowing itself up, our Sun’s predecessor’s nuclear processes created a host of heavy elements like uranium and lead which was then reused when our Solar System and everything in it came into being. This is why all the lead currently found on the Earth was produced when an unstable element like uranium radioactively decayed. Not all the lead that we manage to mine is stable it still contains isotopes – more radioactive versions of itself – still decaying into a more stable element. Only the long passage of time will reduce the amount of alpha-particle emissions.

The bad news is that these alpha-particle emissions can easily wreak havoc by increasing the incidence of errors in the chip circuitry’s operation. And this will only increase as electronic manufacturing firms fabricate finer circuits that are more sensitive to alpha particles. Not to mention lowering the operating voltage of the device in order to reduce power consumption will also increase the error incidents due to alpha-particle interference.

One very effective solution is to consider obtaining the lead used for the manufacture of soldering alloys from sources that are hundreds of years old like lead salvaged from old ships / shipwrecks. Or roofs of 1,000-year-old European cathedrals – any lead that is old enough that its atoms had already decayed into its non-radioactive end products. I consider this a very effective solution because the hi-fi manufacturer Audionote used a similar procedure in obtaining the silver to be used in their audio amplifiers. Audionote only uses silver that’s been out of the ground for at least 30 years. “The older the silver the better” - the company says because they are always mindful on how stray alpha particles affect the sound quality of their products. Though I wonder why only thirty years, did Audionote bought their silver from a mine that uses fission bombs to dig their tunnels since it takes about 30 years for most of the nuclear fallout’s radioactivity to die down? Like if enough strontium 90 is present in the silver used in your audio amplifier, you have other worse things to worry about than how alpha particles can degrade the sound quality of your audio gear. And besides, only half the amount of strontium 90 would have radioactively decayed into something else by 30 years’ time. But given the high level signal that Audionote’s audio amplifiers handle only makes me wonder if this is only a marketing ploy to allow them to jack-up their retail price. Nonetheless, alpha-particle interaction in super small computer chips will be a major issue in consumer electronic manufacturing circles much sooner than later.

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