Tin pest

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Tin medal affected by tin disease PSM V83 D034 Two hundred year old medal affected by tin disease.png
Tin medal affected by tin disease

Tin pest is an autocatalytic, allotropic transformation of the element tin, which causes deterioration of tin objects at low temperatures. Tin pest has also been called tin disease, tin blight or tin leprosy (lèpre d'étain).

A single chemical reaction is said to be autocatalytic if one of the reaction products is also a catalyst for the same or a coupled reaction. Such a reaction is called an autocatalytic reaction.

Allotropy Property of some chemical elements to exist in two or more different forms

Allotropy or allotropism is the property of some chemical elements to exist in two or more different forms, in the same physical state, known as allotropes of the elements. Allotropes are different structural modifications of an element; the atoms of the element are bonded together in a different manner. For example, the allotropes of carbon include diamond, graphite, graphene, and fullerenes. The term allotropy is used for elements only, not for compounds. The more general term, used for any crystalline material, is polymorphism. Allotropy refers only to different forms of an element within the same phase ; differences in these states alone would not constitute examples of allotropy.

Tin Chemical element with atomic number 50

Tin is a chemical element with the symbol Sn (from Latin: stannum) and atomic number 50. Tin is a silvery metal that characteristicly has a faint yellow hue. Tin, like indium, is soft enough to be cut without much force. When a bar of tin is bent the so-called "tin cry" can be heard as a result of sliding tin crystals reforming; this trait is shared by indium, cadmium and frozen mercury. Pure tin after solidifying keeps a mirror-like appearance similar to most metals. However, in most tin alloys (such as pewter) the metal solidifies with a dull gray color. Tin is a post-transition metal in group 14 of the periodic table of elements. It is obtained chiefly from the mineral cassiterite, which contains stannic oxide, SnO2. Tin shows a chemical similarity to both of its neighbors in group 14, germanium and lead, and has two main oxidation states, +2 and the slightly more stable +4. Tin is the 49th most abundant element on Earth and has, with 10 stable isotopes, the largest number of stable isotopes in the periodic table, thanks to its magic number of protons. It has two main allotropes: at room temperature, the stable allotrope is β-tin, a silvery-white, malleable metal, but at low temperatures, it transforms into the less dense grey α-tin, which has the diamond cubic structure. Metallic tin does not easily oxidize in air.

Contents

It was observed in medieval Europe that the pipes of pipe organs were affected in cool climates. As soon as the tin began decomposing, the process accelerated.

Pipe organ wind instrument that produces sound by driving pressurized air (called wind) through pipes selected via a keyboard

The pipe organ is a musical instrument that produces sound by driving pressurized air through the organ pipes selected from a keyboard. Because each pipe produces a single pitch, the pipes are provided in sets called ranks, each of which has a common timbre and volume throughout the keyboard compass. Most organs have many ranks of pipes of differing timbre, pitch, and volume that the player can employ singly or in combination through the use of controls called stops.

With the adoption of the Restriction of Hazardous Substances Directive (RoHS) regulations in Europe, and similar regulations elsewhere, traditional lead/tin solder alloys in electronic devices have been replaced by nearly pure tin, introducing tin pest and related problems such as tin whiskers. [1] [2]

The Restriction of Hazardous Substances Directive 2002/95/EC, (RoHS 1), short for Directive on the restriction of the use of certain hazardous substances in electrical and electronic equipment, was adopted in February 2003 by the European Union.

Solder metal alloy used to join together metal pieces with higher melting points

Solder is a fusible metal alloy used to create a permanent bond between metal workpieces. The word solder comes from the Middle English word soudur, via Old French solduree and soulder, from the Latin solidare, meaning "to make solid". In fact, solder must first be melted in order to adhere to and connect the pieces together after cooling, which requires that an alloy suitable for use as solder have a lower melting point than the pieces being joined. The solder should also be resistant to oxidative and corrosive effects that would degrade the joint over time. Solder used in making electrical connections also needs to have favorable electrical characteristics.

Alloy mixture or metallic solid solution composed of two or more elements

An alloy is a combination of metals or a combination of one or more metals with non-metallic elements. For example, combining the metallic elements gold and copper produces red gold, gold and silver becomes white gold, and silver combined with copper produces sterling silver. Elemental iron, combined with non-metallic carbon or silicon, produces alloys called steel or silicon steel. The resulting mixture forms a substance with properties that often differ from those of the pure metals, such as increased strength or hardness. Unlike other substances that may contain metallic bases but do not behave as metals, such as aluminium oxide (sapphire), beryllium aluminium silicate (emerald) or sodium chloride (salt), an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductility, opaqueness, and luster. Alloys are used in a wide variety of applications, from the steel alloys, used in everything from buildings to automobiles to surgical tools, to exotic titanium-alloys used in the aerospace industry, to beryllium-copper alloys for non-sparking tools. In some cases, a combination of metals may reduce the overall cost of the material while preserving important properties. In other cases, the combination of metals imparts synergistic properties to the constituent metal elements such as corrosion resistance or mechanical strength. Examples of alloys are steel, solder, brass, pewter, duralumin, bronze and amalgams.

Allotropic transformation

At 13.2 °C (about 56 °F) and below, pure tin transforms from the silvery, ductile metallic allotrope of β-form white tin to the brittle, nonmetallic, α-form grey tin with a diamond cubic structure. The transformation is slow to initiate due to a high activation energy but the presence of germanium (or crystal structures of similar form and size) or very low temperatures of roughly −30 °C aids the initiation. There is also a large volume increase of about 27% associated with the phase change to the nonmetallic low temperature allotrope. This frequently makes tin objects (like buttons) decompose into powder during the transformation, hence the name tin pest. [3]

Celsius Scale and unit of measurement for temperature

The Celsius scale, also known as the centigrade scale, is a temperature scale used by the International System of Units (SI). As an SI derived unit, it is used worldwide. In the United States, the Bahamas, Belize, the Cayman Islands and Liberia however, Fahrenheit remains the preferred scale for everyday temperature measurement. The degree Celsius can refer to a specific temperature on the Celsius scale or a unit to indicate a difference between two temperatures or an uncertainty. It is named after the Swedish astronomer Anders Celsius (1701–1744), who developed a similar temperature scale. Before being renamed to honor Anders Celsius in 1948, the unit was called centigrade, from the Latin centum, which means 100, and gradus, which means steps.

Fahrenheit unit of temperature

The Fahrenheit scale is a temperature scale based on one proposed in 1724 by Dutch–German–Polish physicist Daniel Gabriel Fahrenheit (1686–1736). It uses the degree Fahrenheit as the unit. Several accounts of how he originally defined his scale exist. The lower defining point, 0 ℉, was established as the freezing temperature of a solution of brine made from equal parts of ice, water and a salt. Further limits were established as the melting point of ice (32 ℉) and his best estimate of the average human body temperature. The scale is now usually defined by two fixed points: the temperature at which water freezes into ice is defined as 32 ℉, and the boiling point of water is defined to be 212 ℉, a 180 ℉ separation, as defined at sea level and standard atmospheric pressure.

Diamond cubic three-dimensional repeating pattern formed by the atoms of a diamond crystal

The diamond cubic crystal structure is a repeating pattern of 8 atoms that certain materials may adopt as they solidify. While the first known example was diamond, other elements in group 14 also adopt this structure, including α-tin, the semiconductors silicon and germanium, and silicon/germanium alloys in any proportion.

The decomposition will catalyze itself, which is why the reaction speeds up once it starts; the mere presence of tin pest leads to more tin pest. Tin objects at low temperatures will simply disintegrate.

Possible historical examples

Scott expedition to Antarctica

In 1910 British polar explorer Robert Scott hoped to be the first to reach the South Pole, but was beaten by Norwegian explorer Roald Amundsen. On foot, the expedition trudged through the frozen deserts of the Antarctic, marching for caches of food and kerosene deposited on the way. In early 1912, at the first cache, there was no kerosene; the cans – soldered with tin – were empty. The cause of the empty tins could have been related to tin pest. [4] Some observers blame poor quality soldering, as tin cans over eighty years old have been discovered in Antarctic buildings with the soldering in good condition.

Robert Falcon Scott British explorer, leader of expeditions to the Antarctic

Robert Falcon Scott was a Royal Navy officer and explorer who led two expeditions to the Antarctic regions: the Discovery expedition of 1901–1904 and the ill-fated Terra Nova expedition of 1910–1913. On the first expedition, he set a new southern record by marching to latitude 82°S and discovered the Antarctic Plateau, on which the South Pole is located. On the second venture, Scott led a party of five which reached the South Pole on 17 January 1912, less than five weeks after Amundsen's South Pole expedition.

South Pole Southern point where the Earths axis of rotation intersects its surface

The South Pole, also known as the Geographic South Pole or Terrestrial South Pole, is one of the two points where Earth's axis of rotation intersects its surface. It is the southernmost point on the surface of Earth and lies on the opposite side of Earth from the North Pole.

Roald Amundsen Norwegian polar researcher, who was the first to reach the South Pole

Roald Engelbregt Gravning Amundsen was a Norwegian explorer of polar regions and a key figure of the Heroic Age of Antarctic Exploration. He led the second expedition to traverse the Northwest Passage in 1906 and the first expedition to the South Pole in 1911. He led the first expedition proven to have reached the North Pole in 1926. He disappeared while taking part in a rescue mission for the airship Italia in 1928.

Napoleon's buttons

The story is often told of Napoleon's men freezing in the bitter Russian Winter, their clothes falling apart as tin pest ate the buttons. This clearly appears to be an urban legend, and there is no evidence that there existed any failing buttons at all, and thus they cannot have been a contributing factor in the failure of the invasion. [5] Critics of the theory point out that the tin used would have been quite impure and thus more tolerant of low temperatures. Laboratory tests provide evidence that the time required for unalloyed tin to develop significant tin pest damage at lowered temperatures is about 18 months, which is more than twice the length of the invasion. [4] It is clear though that some of the regiments employed in the campaign had tin buttons and that the temperature reached sufficiently low values (below −40 °C or F). [5] However, none of the many survivors' tales mention problems with buttons and it has been suggested that the legend is an amalgamation of a case of disintegrating Russian tin buttons in an army warehouse in the 1860s [6] and the utterly desperate state of Napoleon's army turning soldiers into ragged beggars. [5] [7]

Modern tin pest since adoption of RoHS

With the adoption of the Restriction of Hazardous Substances Directive (RoHS) regulations in Europe and California banning most uses of lead, and similar regulations elsewhere, the problem of tin pest has returned, since some manufacturers who previously used tin/lead alloys now use predominately tin based alloys. For example, the leads of some electrical and electronic components are plated with pure tin. In cold environments, this can change to α-modification grey tin, which is not electrically conductive, and falls off the leads. After reheating, it changes back to β-modification white tin, which is electrically conductive, and can cause electrical short circuits and failure of equipment. Such problems can be intermittent as the powdered particles of tin move around. Tin pest can be avoided by alloying with small amounts of electropositive metals or semimetals soluble in tin's solid phase, e.g. antimony or bismuth, which prevent the decomposition.

See also

Related Research Articles

Printed circuit board Board to support and connect electronic components

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Carbon group group of chemical elements

The carbon group is a periodic table group consisting of carbon (C), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), and flerovium (Fl). It lies within the p-block.

Flux (metallurgy) type of chemicals used in metallurgy

In metallurgy, a flux is a chemical cleaning agent, flowing agent, or purifying agent. Fluxes may have more than one function at a time. They are used in both extractive metallurgy and metal joining.

Fernico describe a family of metal alloys made primarily of iron, nickel and cobalt. The family includes Kovar, FerNiCo I, FerNiCo II, and Dumet. The name is made up of the chemical symbols of its constituent three elements. "Dumet" is a portmanteau of "dual" and "metal," because it is a heterogeneous alloy, usually fabricated in the form of a wire with an alloy core and a copper cladding. These alloys possess the properties of electrical conductivity, minimal oxidation and formation of porous surfaces at working temperatures of glass and thermal coefficients of expansion which match glass closely. These requirements allow the alloys to be used in glass seals, such that the seal does not crack, fracture or leak with changes in temperature.

Terne plate is a form of tinplate: a thin steel sheet coated with an alloy of lead and tin. The terne alloy was in the ratio of 10-20% tin and the remainder lead. The low tin content made it cheaper than other tinplates.

Wave soldering Electronics soldering process

Wave soldering is a bulk soldering process used in the manufacture of printed circuit boards. The circuit board is passed over a pan of molten solder in which a pump produces an upwelling of solder that looks like a standing wave. As the circuit board makes contact with this wave, the components become soldered to the board. Wave soldering is used for both through-hole printed circuit assemblies, and surface mount. In the latter case, the components are glued onto the surface of a printed circuit board (PCB) by placement equipment, before being run through the molten solder wave. Wave soldering is mainly used in soldering of through hole components.

Plating is a surface covering in which a metal is deposited on a conductive surface. Plating has been done for hundreds of years; it is also critical for modern technology. Plating is used to decorate objects, for corrosion inhibition, to improve solderability, to harden, to improve wearability, to reduce friction, to improve paint adhesion, to alter conductivity, to improve IR reflectivity, for radiation shielding, and for other purposes. Jewelry typically uses plating to give a silver or gold finish.

Whisker (metallurgy) Phenomenon in electrical devices

Metal whiskering is a phenomenon which occurs in electrical devices when metals form long whisker-like projections over time. Tin whiskers were noticed and documented in the vacuum tube era of electronics early in the 20th century in equipment that used pure, or almost pure, tin solder in their production. It was noticed that small metal hairs or tendrils grew between metal solder pads causing short circuits. Metal whiskers form in the presence of compressive stress. Zinc, cadmium, and even lead whiskers have been documented. Many techniques are used to mitigate the problem including changes to the annealing process, addition of elements like copper and nickel, and the inclusion of conformal coatings. Traditionally, lead was added to slow down whisker growth in tin-based solders.

Gold plating

Gold plating is a method of depositing a thin layer of gold onto the surface of another metal, most often copper or silver, by chemical or electrochemical plating. This article covers plating methods used in the modern electronics industry; for more traditional methods, often used for much larger objects, see gilding.

Solid solution Chemical solution in solid form; whose solvents crystal structure is not altered by solute

A solid solution is a solid-state solution of one or more solutes in a solvent. Such a multi-component system is considered a solution rather than a compound when the crystal structure of the solvent remains unchanged by addition of the solutes, and when the chemical components remain in a single homogeneous phase. This often happens when the two elements involved are close together on the periodic table; conversely, a chemical compound generally results when two metals involved are not near each other on the periodic table.

Dip soldering

Dip soldering is a small-scale soldering process by which electronic components are soldered to a printed circuit board (PCB) to form an electronic assembly. The solder wets to the exposed metallic areas of the board, creating a reliable mechanical and electrical connection.

The Occam process is a solder-free, Restriction of Hazardous Substances Directive (RoHS)-compliant method for use in the manufacturing of electronic circuit boards developed by Verdant Electronics. It combines the usual two steps of the construction of printed circuit boards (PCBs) followed by the population process of placing various leaded and non-leaded electronic components into one process.

Soldering process of joining metal pieces with heated filler metal

Soldering is a process in which two or more items are joined together by melting and putting a filler metal (solder) into the joint, the filler metal having a lower melting point than the adjoining metal. Unlike welding, soldering does not involve melting the work pieces. In brazing, the work piece metal also does not melt, but the filler metal is one that melts at a higher temperature than in soldering. In the past, nearly all solders contained lead, but environmental and health concerns have increasingly dictated use of lead-free alloys for electronics and plumbing purposes.

Failure of electronic components Ways electronic elements fail and prevention measures

Electronic components have a wide range of failure modes. These can be classified in various ways, such as by time or cause. Failures can be caused by excess temperature, excess current or voltage, ionizing radiation, mechanical shock, stress or impact, and many other causes. In semiconductor devices, problems in the device package may cause failures due to contamination, mechanical stress of the device, or open or short circuits.

Materials for use in vacuum

Materials for use in vacuum are materials showing very low rate of outgassing in vacuum, and, where applicable, tolerant to the bake-out temperatures. The requirements grow increasingly stringent with the desired degree of vacuum achievable in the vacuum chamber. The materials can produce gas by several mechanisms. Molecules of gases and water can be adsorbed on the material surface. Materials may sublimate in vacuum. Or the gases can be released from porous materials or from cracks and crevices. Traces of lubricants, residues from machining, can be present on the surfaces. A specific risk is outgassing of solvents absorbed in plastics after cleaning.

Chromium hydrides are compounds of chromium and hydrogen, and possibly other elements. Intermetallic compounds with not-quite-stoichometric quantities of hydrogen exist, as well as highly reactive molecules When present at low concentrations, hydrogen and certain other elements alloyed with chromium act as softening agents that enables the movement of dislocations that otherwise not occur in the crystal lattices of chromium atoms.

Conductive anodic filament, also called CAF, is a metallic filament that forms from an electrochemical migration process and is known to cause printed circuit board (PCB) failures.

References

  1. Burns, Neil Douglas (Oct 2009), "A Tin Pest Failure", Journal of Failure Analysis and Prevention, 9 (5): 461–465, doi:10.1007/s11668-009-9280-8, ISSN   1864-1245 , (Print) ISSN   1547-7029
  2. Tin Pest Control National Physical Laboratory, www.npl.co.uk[ dead link ]
  3. Janey Levy Tin, The Rosen Publishing Group, 2009, ISBN   1-4358-5073-4, page 20
  4. 1 2 Adams, Cecil (May 2, 2008). "Did tin disease contribute to Napoleon's defeat in Russia?". The Straight Dope . Retrieved 17 August 2010.
  5. 1 2 3 Öhrström, Lars (2013). The Last Alchemist in Paris. Oxford: Oxford University Press. ISBN   978-0-19-966109-1.
  6. Fritsche, Carl (1869). "Ueber eigenthumlich modificirtes Zinn" (PDF). Berichte der Deutschen Chemischen Gesellschaft. 2: 112–113. doi:10.1002/cber.18690020156.
  7. Zamoyski, Adam (2004). Napoleons Fatal March on Moscow. New York: Harper Perennial.