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I'm curious which company started using the standard 0.1 in (2.54 mm) pin pitch for components. This is surprisingly difficult to Google. I see 1956 and Cicoil Corporation when it comes to ribbon cables but I doubt this was the first use.

On one hand, a tenth of an inch is kind of an obvious measurement to use, speaking as an American. On the other hand, I suspect that the choice had just as much to do with the manufacturing capability of "the time" (whatever "the time" was). For example, now we also have pins twice as dense (0.05 in), but the legacy of the original choice remains.

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  • \$\begingroup\$ Not so much 1/10th of an inch as much as 100 mils. \$\endgroup\$
    – DKNguyen
    Commented Dec 6, 2019 at 17:22
  • \$\begingroup\$ Don't know for sure, but if I were to guess it would have to one of the early players in the digital logic field, late 60s. That would point to Texas Instruments, Fairchild, etc. Some of the early digital ICs were packaged in TO-5 can packages, which is what was being used for transistors and analog ICs such as op amps. \$\endgroup\$
    – SteveSh
    Commented Dec 6, 2019 at 17:57
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    \$\begingroup\$ This is from Wikipedia, using the search term "DIP package". "The dual-inline format was invented by Don Forbes, Rex Rice and Bryant Rogers at Fairchild R&D in 1964,when the restricted number of leads available on circular transistor-style packages became a limitation in the use of integrated circuits." The DIP package style had pins on 0.1" pitch. \$\endgroup\$
    – SteveSh
    Commented Dec 6, 2019 at 18:08
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    \$\begingroup\$ 100 mils.spaced connectors probably around for 100 yrs used by US military \$\endgroup\$
    – D.A.S.
    Commented Dec 6, 2019 at 18:30

2 Answers 2

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One of the first IC packages was the flat pack, which had 0.05" pin pitch. "The original flatpack was invented by Y. Tao in 1962" (at Texas Instruments).

The relaxed 0.1" pitch would have seemed a natural for commercial products, and the DIP package came along a couple years later.

Before that, the TO-5 transistor package had a 0.1" pitch, albeit with the center lead offset by 0.1". Fairchild sold those commercially (2N697) in mid-1958 so they date back at least that far.

Before PCBs became popular the pin pitches were not particularly important and early connectors often had oddball dimensions. Octal tube bases were on an 11/16" circle so I suppose we should be grateful they didn't go with 3/32" or something like that. I believe the Russians had DIP packages with 2.5mm pitch pins.

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  • \$\begingroup\$ Coincidentally, 2.5mm is very close to 0.1 in. (precisely 0.0984 in). \$\endgroup\$
    – mach128x
    Commented Mar 8, 2021 at 21:20
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According to Wikipedia, at least for IC packages:

The dual-inline format was invented by Don Forbes, Rex Rice and Bryant Rogers at Fairchild R&D in 1964,[3] when the restricted number of leads available on circular transistor-style packages became a limitation in the use of integrated circuits.

We can guess, since this is an American company in an era long before metric dimensions became common in manufacturing, that 0.1" was an "obvious" choice.

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