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What's the minimum lead length for a component in order to reliably connect with solderless breadboard contacts?

Reading specs on cables, relays LEDs, and other components, what should I take as the minimum distance from the bottom of the device to the tip of the lead? Or put another way, from the top of the breadboard to the pinch-point of its contacts?

I want to plug into a generic solderless breadboard and not worry about loose connections. I have assumed through-hole PC board leads would be sufficient but occasionally they are not. Case in point, a flex cable from Digi-Key has leads that are about 3.2mm or 0.125in long that keep falling out. So the answer may be just a little longer than that.

This spec from 3M says nothing about this dimension, except that the standard interconnect wires go about 0.250in deep.

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  • \$\begingroup\$ You want the "minimum insertion depth" from an actual datasheet, not an ad. \$\endgroup\$
    – Passerby
    Commented Aug 13, 2014 at 17:05
  • \$\begingroup\$ "I want to plug into a generic solderless breadboard and not worry about loose connections." <-- good luck with that. \$\endgroup\$
    – markrages
    Commented Aug 13, 2014 at 21:46
  • \$\begingroup\$ Ever seen any such data sheet @Passerby? I couldn't find one. It would constitute an answer, I agree. I found that ad/spec from a datasheet link at DigiKey. \$\endgroup\$
    – Bob Stein
    Commented Aug 15, 2014 at 13:12

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A standard DIP has a lead length of about 0.125" (3.1mm) but the actual penetration below the surface is probably more like 4.2mm because the holes and leads are both beveled.

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    \$\begingroup\$ How do bevels make penetration deeper from 3.1 to 4.2mm, @SpehroPefhany? I'd think lead bevels would mean less effective depth. And hole bevels would only make penetration easier not deeper. Have you seen a standard on dip leads? \$\endgroup\$
    – Bob Stein
    Commented Aug 15, 2014 at 13:18
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    \$\begingroup\$ There's probably a MIL standard, but drawings differ. Normally the bottom of the DIP package sits up above the PCB by a small amount- the spacing is set by the leadframe shape. This is by design to avoid trapping anything under the package. On a solderless breadboard, I think you'll find the bottom of the package sits right down on the plastic (don't have one in front of me). \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented Aug 15, 2014 at 13:42
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The pins on the male jumper cables that came with my Raspberry Pi starter kit are about 8 mm/5/16".

For a specific breadboard, I'm sure this dimension can easily be determined experimentally.

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  • \$\begingroup\$ Was hoping for some kind of standard or spec I could rely on when ordering breadboards or components. Your number may be the closest to it. \$\endgroup\$
    – Bob Stein
    Commented Aug 15, 2014 at 13:20
  • \$\begingroup\$ There is probably not any "Official Spec", but the breadboards are designed to hold standard DIP ICs, so you should be able to use the length of a DIP pin as a reasonable minimum insertion length. \$\endgroup\$
    – Peter Bennett
    Commented Aug 17, 2014 at 20:17

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