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Bell Telephone Laboratories - Tin Whiskers
December 1955 Radio & Television News

July 1955 Radio & TV News
July 1955 Radio & Television News Cover - RF Cafe[Table of Contents]

Wax nostalgic about and learn from the history of early electronics. See articles from Radio & Television News, published 1919-1959. All copyrights hereby acknowledged.

Lead-Free Pb-Free - RF CafeThe famous words of Jorge Agustín Nicolás Ruiz de Santayana y Borrás (aka George Santayana) immediately came to mind when I saw this Bell Telephone Laboratories advertisement in a 1955 issue of Radio & Television News magazine: "Those who cannot remember the past are condemned to repeat it." Anyone involved in the electronics field at the beginning of the lead-free (Pb-Free) craze in the early 2000's probably remembers the purportedly unexpected phenomenon of tin whiskers growing out of lead-free solder joints and wreaking havoc with the short circuits caused when whiskers between adjacent elements made contact. The problem appeared with closely spaced connector pins, fine pitch integrated circuit packages, high density surface mount circuit board layouts, etc. Military and aerospace engineers and scientists had fits initially trying to figure out what was going on. As it turns out, the issue was known and dealt with half a century earlier. In the rush to reduce the presence of lead by a miniscule fraction in the electronics industry, a huge problem was created. Keep that in mind when you see that Pb-Free RoHS symbol now so proudly displayed by vendors.

Bell Telephone Laboratories Ad

Tin Whiskers, Bell Telephone Laboratories, December 1955 Radio & Television News - RF CafeWhiskers on tin-plated steel, enlarged 6 times. Immense yield strength of metals in whisker form was discovered by Bell scientists.

The clue of the metal whiskers

The habit of close observation at Bell Laboratories often turns "tremendous trifles" into important scientific progress. Such a case occurred when unexplained short circuits in wave filters seemed to be associated with a zinc-plated mounting bracket.

Close scrutiny disclosed a whiskery growth on the zinc plating. Similar whiskers of tin were found growing on tin-plated equipment. Studies showed the whiskers to be tiny single crystals of metal.

Suspecting that these unusual crystals might be of essentially perfect structure, alert Laboratories scientists saw an opportunity at last to test an important metallurgical theory.

The scientists studied the whiskers, grew larger ones, and showed that the crystals had enormously high yield strength as predicted by the theory for perfect crystals - a strength far greater than for the same metal in any other known form. This clue has opened new frontiers in the study of what makes metals strong or weak, and has excited metallurgists all over the world.

Thus, another new advance has come out of the Bell Telephone Laboratories practice of scrutinizing everything that can play a part in better telephone service. Through the study of thousands of specially cultivated whiskers, Bell scientists seek to prevent treacherous growths in telephone equipment.

Bell Telephone Laboratories

Improving Telephone Service for America Provides Careers for Creative Men in Scientific and Technical Fields

 

 

Posted August 25, 2020

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