PCB Assembly Services – Screaming Circuits: 150 Years of Predicting the Elements of Electronics: Part 4

A Few Words from Sara Shepherd, Screaming Circuits Contributing Blogger…

Welcome back to our fourth installment celebrating the 150th anniversary of the Periodic Table and the elements in it that make circuitry possible. Today we take a closer look at palladium (Pd, atomic number 46). This soft and shiny silver-white metal resembles its chemical cousin (called a congener by chemists) platinum, but is rarer than both platinum and gold.

Palladium was discovered in 1803 by an English chemist named William Hyde Wollaston. Wollaston had received a metallic sample from South America which seemed to contain only platinum. However, when he dissolved the sample in a mixture of nitric acid and hydrochloric acid, he found that a second element was left behind. He named the new element palladium, after the asteroid Pallas, which had been discovered two months earlier.

You might think Wollaston would rush to tell the world about his discovery but, as we learned in our previous posts, claiming you had found a new element was often met with skepticism – and sometimes mockery – by fellow chemists. Because of this, Wollaston took a unique and entertaining approach to announcing the element.

Keeping his identity a secret, Wollaston put some of the metal up for sale in a London mineral shop. Meanwhile, he also advertised its properties in anonymous handbills which he posted around the city. As Wollaston expected, his claims about the metal were met with skepticism. Another chemist, Richard Chenevix, declared palladium to be a hoax.

Wollaston took things a step further and anonymously offered a reward of £20 for 20 grains of synthetic palladium alloy (not a bad reward in 1803). In an interesting turn of events, his harshest critic Richard Chenevix ended up receiving an award in 1803 after publishing his experiments on palladium, which he incorrectly concluded was an alloy of mercury and platinum. It would be two years until his research was proven unsound.

In the meantime, Wollaston kept his head down and continued working. In 1805, he discovered another element, rhodium (Rh atomic number 45), and was invited to speak at the Royal Society of London. During his discussion of rhodium, Wollaston also shared his original work on palladium and revealed himself as the element’s discoverer at the end of his speech. With his research now public, Chenevix’s claims were dismissed and Palladium was accepted as a new element shortly afterward.

Palladium is highly resistant to corrosion in air and to the action of acids, and has an amazing ability to absorb hydrogen (up to 900 times its own volume). Because of its resistance to corrosion, a major use for palladium is as electrodes within multilayer ceramic capacitors (MLCC). These capacitors can be made quite small, and so you’ll have palladium within electrical appliances like wide screen televisions, computers and mobile phones. Smaller amounts of palladium are found in conductive tracks in hybrid integrated circuits (HIC) and for plating connectors and lead frames.

While valuable in electronic applications, more than half of all available palladium is used by the automotive industry to create catalytic converters. First introduced in 1989, these tube-like structures are coated with palladium and placed within the exhaust systems of cars to convert up to 90% of the harmful gases in exhaust (like hydrocarbons and carbon monoxide) into less noxious substances.

Applications for palladium continue to be discovered. Most recently, DuPont began experimenting with palladium as a means to remove carcinogens from water, essentially creating a catalytic converter for water instead of car exhaust.

MLCCs have been a bit scarce lately. Could palladium be the culprit? Perhaps, perhaps not. Regardless, supply of capacitors is opening up and we have a pretty good handle on it now. If you are still having troubles, we can help.

If you need some prototypes or small production volumes built up, drop on over to our Screaming Circuits website and get an online quote and maybe place an online order. If you’re past that stage and need forecasted or Kanban volume manufacturing, box build and program management, or original electronics design, contact us and ask about our Milwaukee Electronics EMS (Electronics Manufacturing Services) division. Stepping back further in the process, our San Diego PCB division is here for complex and critical PCB layout.

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