Which side of machined pin header should I solder?

[amundsen]

Hello,

I want to solder male machined pin headers to an Arduino Pro Mini because it will allow to connect it to female machined pin headers, which have lower profile than regular pin headers. However, it is not clear for me which side should be soldered to the Arduino and which side should be used for connection to female headers.



I suspect the side with the flat metallic cylinders between pins and plastic part should be soldered as it is the case for the female headers (see second picture) but I'd be happy to have a confirmation. Any argument for/against this choice is welcome too.



Thank you in advance.

[pwillard]

The smaller pin is for the socket

[larryd]

I agree.
However, if you every intend on un soldering and removing the header later, you may have more trouble doing so.

[DrAzzy]

The side with the metal cylinder visible is the one you want to solder, your reasoning is sound.

[DuaneDegn]

The smaller pin is for the socket

Are you sure?

I don't think that is correct. Now I'm not so sure.

@amundsen, I suggest holding off soldering until we're sure. I think pwillard was correct.

Edit: The datasheet I'm looking at makes me think pwillard is correct (though I'm still not convinced).

[DrAzzy]

IIRC, they don't even fit together the wrong way... have you tested fit by hand?

[DuaneDegn]

IIRC, they don't even fit together the wrong way... have you tested fit by hand?

The ones I have fit either way. One way is more secure (with the fat pin used as the connector).

I think the thin end is for soldering since it's the same diameter and the solder pin on the female connectors.

Edit: I was wrong about the thin end being the same.

[amundsen]

Actually both sides can be used on the headers I have. The side with the pillars are a bit harder to push but then seem also harder to remove, which is a good thing I presume. So I think I'll solder the thinner pins to the board.

[DuaneDegn]

Actually both sides can be used on the headers I have. The side with the pillars are a bit harder to push but then seem also harder to remove, which is a good thing I presume. So I think I'll solder the thinner pins to the board.

I've done it the same way myself but I think I've been using them the wrong way around. The flat area around the thicker pins allows a secure solder connection with the pad on the PCB. While the pins will certainly work either way, I think the pins were designed to be used as suggested by pwillard.

When the thin pins are soldered to the board, the thick round area surrounding the thicker pins, doesn't serve any purpose (at least none I can think of).

[alnath]

Actually both sides can be used on the headers I have. The side with the pillars are a bit harder to push but then seem also harder to remove, which is a good thing I presume. So I think I'll solder the thinner pins to the board.

then why do you ask, if you do the exact contrary of what people told you ? 

with 8 pins, it is only a little harder to remove, but it would be really harder with 16, 20 or more pins

[pwillard]

flat area around the thicker pins allows a secure solder connection

Can't be said any plainer than that.

[Paul__B]

Actually both sides can be used on the headers I have. The side with the pillars are a bit harder to push but then seem also harder to remove, which is a good thing I presume.

Well, just as long as you never intend to plug anything else into the socket, as you will most likely have distorted the spring contacts.

So in fact, if you have tried both sides in the socket, you may have already loosened the contacts to the extent that it will be less secure when you use the side with the thinner pins.

As an aside, it would probably not be a good idea in any case to rely on a single row of pins to mount a PCB.  An additional standoff or a second row of pins - such as the Arduino shields use - is certainly more appropriate.