I know that nowadays tantalum is very common in computer components, specifically capacitors, due to its desirable electrical properties. I'm curious when it was first used specifically in the context of computing, and for what purpose.

Bonus: did the computer spur the use of tantalum (that is, was tantalum useless before computers took off) or were computer engineers looking for something that had desirable properties and found that tantalum, being used elsewhere, would do the job?

This question is migrated from retro-computing here.

Some research I've done tells me that Bell Labs required a new type of capacitor for their new transistor, but it was Sprague Electric who made them into something commercially viable somewhere around 1956. However, I don't know when the merger of the tantalum cap and the computer happened, which is what I'm looking for.

  • \$\begingroup\$ as an aside, they had a horrible habit of failing short circuit. I once fixed an early digital reverb unit made by Lexicon which had been in a studio that had suffered lightning strike. I had to change just about every tant decoupling cap. On 4 processor boards and an analogue IO board. That was a lot of caps ... \$\endgroup\$ – danmcb Aug 13 '19 at 7:12

There's a fair bit of history and references in the Wikipedia article, so it's worth exploring those.

We were certainly using tantalum capacitors in industrial electronics long before the personal computer was available, and I'm sure it was used in military electronics as well.

Very early (pre-IBM, eg. S-100) desktop computers probably had a few tantalum caps in them, there appears to be one in this photo of a static RAM board (the blue input cap for the local linear voltage regulator), but most of the bypass caps appear to be ceramic. They would have been sold in the mid-to-late 1970s.

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    \$\begingroup\$ I had tantalum capacitors in military kit in the 1970s (designed in the 50s and 60s, mainly) and we had warning notices in the workshop about the toxic fumes they could emit if they failed in a pyrotechnic manner. They were certainly used in analog computers (the AN-AWG 10/11/12 series radars used a lot of them). \$\endgroup\$ – Peter Smith Aug 12 '19 at 13:56
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    \$\begingroup\$ @PeterSmith And they DID sometimes fail in a pyrotechnic manner with surge or ripple current, even within the ratings. I remember workbenches and PCBs with holes in them where the tantalum slug burned almost completely through. We never had the toxic fume warning, so I probably breathed in some terrible stuff from time to time :) \$\endgroup\$ – John D Aug 12 '19 at 15:56
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    \$\begingroup\$ @JohnD Still DO go off, but most of us have learned to protect, avoid or severely derate them (eg. 1/3 voltage rating and/or several ohms in series). \$\endgroup\$ – Spehro Pefhany Aug 12 '19 at 15:58
  • \$\begingroup\$ SMT Solid Tants (MnO2 types at least) are damaged simply due to reflow and can fail well below their rated voltage if powered from a low impedance high current source. Size D and larger are primarily affected. \$\endgroup\$ – Peter Smith Aug 13 '19 at 8:51

The first tants were around as early as the 1930s. These were foil types. The more modern sintered slug types were from the 1950s from Sprague. Other people researched tantalums but Sprague put it all together.

  • \$\begingroup\$ Are the 1950s types already dry, or still full of sulfuric acid? \$\endgroup\$ – rackandboneman Aug 13 '19 at 2:21
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    \$\begingroup\$ There were wet slug parts early on but these (mostly) gave way to dry slugs, manganese dioxide. Wet slug types can operate to 200C so there may be some made even now. I'm pretty sure the foil parts are totally gone. \$\endgroup\$ – Robert Endl Aug 13 '19 at 3:01
  • \$\begingroup\$ The wet slug types I've seen looked more like oil capacitors, not teardrops... \$\endgroup\$ – rackandboneman Aug 13 '19 at 11:21

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