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Two-row connector blocks are ubiquitous in small-run and hobbyist PCB designs. Pitches of 0.1" or 2mm are the most common, and there are all sorts of options for board-to-board or board-to-wire connectors. The problem is that pin numbering schemes vary wildly.

Pin numbering schemes I've seen include:

  1. DIP-style counterclockwise: DIP number scheme, taken from Wikipedia
  2. Zig-zag between the two rows: Molex Milligrid numbering scheme
  3. Down one row then the other, but NOT counterclockwise: Molex Micro-fit numbering scheme

In my experience, getting the pin numbers wrong is one of the most common sources of PCB heartbreak. I've done a lot of wire patching to correct 6-pin header layout mistakes... and I've thrown away boards with 70-pin header errors.

My question is: Are there industry standard terms for these (or other) 2-row pin numbering schemes?

I would love to have a short, reliable way to specify these schemes, to allow saying things like "We're using a 14-pin 0.1" header with zig-zag numbering" (or whatever).

Although standardized names with the broadest possible user base are (obviously) better, I realize that there probably isn't one true answer to this question. I'd appreciate answers about how these schemes are named even within smaller subsets of the industry, as long as you're clear about the scope of use (e.g. "At company X we always called the second scheme 'shoelacing'").

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    \$\begingroup\$ xkcd.com/927 \$\endgroup\$
    – Lior Bilia
    Commented Apr 13, 2014 at 15:14
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    \$\begingroup\$ I don't know of any standard naming scheme. Sometimes the connector manufacturer doesn't specify a scheme, sometimes it's on the mechanical drawing. It's a dog's breakfast. \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented Apr 13, 2014 at 20:06
  • \$\begingroup\$ The problem is the pin-out of male connector is mirror image of the female. So if the male connector is 1234 on row 1 and 5678 on row 2, the female would be 4321 on row 1 and 8765 on row 2. Better get a few samples first before doing the land pattern! \$\endgroup\$
    – daniel
    Commented Sep 12, 2019 at 9:56

3 Answers 3

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If the connector is not made to a certain specification, say IEC60603-2, the manufacturer could make it any way they like.

I have not seen a "default" standard yet.

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If You are using/connecting flat/ribbon cable than pin numbering must be zig-zag, because of cable construction. It is also depending on software you are using for develop pcb. In my experience in repairing boards, more or less 1st pin is somehow visibile, other wires mark as for your convenience. Happy HW connecting.

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  • \$\begingroup\$ I've taken the flat/ ribbon requirement as reason enough to standardize around "zig-zag" and always use that for my PCBs. It's certainly not idea, especially when some vendors "standardize" a different way when the manufacturer doesn't weigh in, but at least it's internally consistent. Ugh. (... and lots of comments on schematics about this when things get "non-standard.") \$\endgroup\$
    – Casey
    Commented Apr 8, 2020 at 20:32
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Pin 1 generally gets a square pad on the PCB as an index marker, whereas those of the other pins are generally round.

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