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Alright, I will try to formulate this as a non-shopping question... let's hope I can make it so.

I do have a board (which I can still change) which basically has 1 hole in each corner. This board, features some (user-accessible) connectors on one side (USB, ...) and now I'm looking for a way to fix this board to some mainboard.

I would like to be able to fix the board either horizontally or vertically, the required pin count is around 150 (including power and ground).

What I am looking for is a way to mount the board either way with as few additional components as possible. I also have the option to mount it to the casing in either direction but I'd rather have a version where the board is really tied to the mainboard (and to the casing).

The main question is now: Do you have another idea than using a 90° 1.27mm (0.05'') pin header?

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If the requirement is "as few additional components as possible", then the answer is probably some kind of edgecard connector. This requires only one additional component, probably a connector mounted on the main card. Connection to the daughter card is made through a pattern etched in copper on the daughter card.

enter image description here

It should be possible to find a family of connectors that allows either a horizontal or vertical connection.

enter image description here

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    \$\begingroup\$ Be aware that if you do use an edge-connector, and you want decent reliability, you are pretty much going to have to have the copper on the board gold-plated, at least around the edge tines. Unplated boards will work for testing, but are not reliable over the long-term. \$\endgroup\$ – Connor Wolf May 17 '13 at 4:55
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You might use a short ribbon cable for the electronic connection, allowing the board to rotate 90 degrees while staying connected. Then the mechanical connection could be made via any other method, including standoffs or spacers or some other structure.

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Two sections of 80 conductor ribbon cable. That way you could even use standard dual row headers. Or you would need to use high conductor count FPC.

Backplane connectors would be another option. Mainboard will plug into backplane, daughterboard plugs into a second one for horizontal, or a third for vertical.

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If cost and ease of availability are factors, then:

  • Use two Ultra-DMA IDE (80-connector) ribbon cables, each with Insulation-Displacement Connectors.
  • Use the corresponding 40x2 fine-pitch IDC receptacles which are available in both vertical and horizontal configurations, 2 on each board (mainboard and accessory board)
  • If you have the option, put the receptacles well-separated along the "joining edge", such that an accidental wrench does not pull off the cables.
  • Of the 160 conductors available between the boards, use 150 for the currently assigned lines, and the remaining 10 distributed 5 each for power and for ground.
  • Now mount the two boards mechanically using L-brackets, such as used in some PC cabinets.
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