Board to board interconnection

Samtec, AMP, Molex and others make a range of board stacking connectors designed specifically for this sort of application. Note that they specifically accomodate pins going through a board for a 'top mounted' connector with pins coming up from the bottom on some lines.

Check out their offerings. 21mm is not a 'standard' stack height, but they may have something.

If not, then I would use IDC connectors (0.050" pitch) to connect up the two boards. That would require a standard connector on each board and a standard (40 way) IDC ribbon cable between the two.

FFC can be a beast to deal with and I use it, but only in those areas I have no space for other solutions (or where that's the interface already).

Cheers

PeteS

It may be overkill for just 2 boards, but the tidy way is a backplane with card-edge sockets. The rear of the backplane can have screw connectors for external connections.

I like having all my circuitry on boards that just 'unplug' for ease of diagnosis, repair, and replacement.

Luhan

You didn't say whether or not you need to be able to quickly separate them, so why not just put identical pad patterns on both boards and run hardwires between the boards?

You also didn't say whether you were planning on two boards or two million boards. The techniques are a lot different.

Jim

you can get long dual row .1" spacing header pins solder to one board and mating socket on the other board.

Colin =^.^=

Graham

They have to be mated once only one during assembly and potentially for repair later.

Qty are 100-200 units.

Ricky

In which case I would suggest a through-board stack pair.

Samtec makes a nice range (See Graham's link above)

Cheers

PeteS

You could use a short flat cable without the connectors - just solder it in!

Like these:

PS:

Flexible pcb's is just the thing for those pesky mil-std round connectors, BTW!!