Preferences: Male or Female connector on board

Question

On a prototyping board for use by students, should one place male (pin) headers or female headers on the PCB, considering that most of the pins will be unused most of the time.

I'm inclined to place the female headers on the PCB and have male pins attached to all cabling respectively. This way touching unused, open contacts by accident is less of an issue. But checking through catalogues (Hirose, Molex,..) I see lots of male headers for PCB mounting but few female ones.

Is my reasoning backward? What I am missing?

Conclusion:

Considering all comments of this thread I am inclined to use male connector pins on the board. Doktor J has given a nice example of a shrouded pin header that would even provide some polarization, albeit I will probably use a 2mm pitch for compactness.

Even better if those were side-stackable, that is if I could place like 2x20 holes in a row and have shrouded connectors of different width (say either 2x 2x10, or 4x 2x5, or a single 2x20) attached. However, this is not possible with the typical box-shape shrouding.

Solution I just discovered FCI Minitek Headers. These are side-stackable and have polarization and shrouding. I'll go with these.

Answer 1

Generally, proper design dictates that - for safety's sake - pluggable connectors supplying power do so using female contacts because, being shrouded, they're less likely to accidentally wind up causing a catastrophe when they're unplugged and hot.

Answer 2

Convention suggests that you should always have male pin headers on the board and female connectors on the cables. I imagine the idea behind this is that the board is generally mounted in some sort of enclosure that protects it from accidental shorts, whereas if a cable is connected to the header and the other end is left hanging, female connections on the cable will prevent it from flopping around and coming into contact with the metal chassis or something else that power or signal pins shouldn't touch.

If your concern is a stray tool accidentally coming into contact with the board connector, you can look into a shrouded pin header connection such as this one from SparkFun:

While it doesn't offer complete contact protection, a stray wire or screwdriver is much less likely to short the pins. Then, if the students leave the board side of the cable connected and it's hanging loose, you don't have to worry about bare pins bumping into something Bad.

Lastly, another consideration is convenience: not only is it easier to find male pin headers, it's much easier to find female IDC connectors for ribbon cable, or just premade cables to save you that much work.

Answer 3

Male connectors (comparisons to the human condition wisely avoided) tend to be relatively simple and trouble-free. Damage is usually easily visible.

By their very function female receptacles tend to be more complex and prone to damage or contamination, so I prefer to put the male part on the board where damage is generally more costly, all other things being equal.

Of course if power is coming off you want to prevent trouble so that may dictate what gets used where. You don't want live mains voltage on an exposed male pin (or female connector) where someone could get shocked or a short could cause damage. Barrel connectors as used in wall wart cords, which are by most estimates female in nature, actually have an exposed outer surface which can short. Not usually an issue, but I've seen non-isolated auto cigar plug adapters that have positive voltage on the barrel (and thus a voltage relative to chassis ground). If it touches grounded metal, a short occurs.

Answer 4

For your simple pin-and-socket ribbon type connections, the pin can be rigidly attached to the motherboard, while a socket, by its nature, flexes and cannot be as rigidly attached. On the other hand, since the socket must have a plastic surround, etc, it is well-suited for attaching to the end of a cable.

A secondary issue is that the socket is more easily damaged than the pin, and a cable is usually cheaper to replace than a motherboard.

A convenient feature of having the pin on the board is that jumpers can easily be used on the same "headers" that are used for cables, so fewer part numbers need to be stocked.

And another detail: Pin headers are a lot easier than sockets to get installed on a board without damage using automated equipment, flow soldering, etc.