Developement board design suggestions

[Garth]

Been rethinking the daughter board arrangement and contemplating using edge card connectors instead of headers. Would allow more room on main board w/ all the options thus a lower cost.
What is your feeling on edge card verses headers. It was mentioned several years ago that edge card is old school but they are still used so can't be all that bad.

I used the pin header on the 4Mx8 10ns 5V SRAM hobby module I sell, and the dual-row connector takes about 0.200" of the edge of the board.



(There are ICs on both sides. The picture shows up larger than actual size on my monitor.) You can go with straight or right-angle pins. Pin headers and sockets can be cut to any length but IDCs (for ribbon cable) cannot, and IDCs come in 10, 16, 20, 26, 34, 40, and 50 pins. IDCs are much better for ribbon cable than board-edge connectors though, and although I have not checked recently, I think they're cheaper. Pin headers can be replaced if damaged, whereas board-edge contacts cannot.

[brad]

Pin headers can be replaced if damaged, whereas board-edge contacts cannot.

Very good point. And as far as costs go, pin headers are dirt cheap, especially if bought in bulk quantities.

[MrDEB]

Been rethinking this and perhaps use a double row female connector on both the boards then insert a double row "breakaway" male pins to allow replacement in even of breakage.
Just need to find a female header that can be soldered to a boards edge. Been wondering if just soldering through hole female headers to edge using SMD pads to solder to. Would cut the cost way down instead of a right angle header.

[brad]

I think you could just solder standard female connectors to the edge but I would recommend getting thicker PCB's than normal - perhaps 2mm would do the job nicely?

[MrDEB]

I think I found solution
Harwin connectors pn# M50-3002045 a female socket w/ 1.27 pitch so can be soldered to pcBoard SMT pads. Need 4 @ $3.48 each need 5 if ribbon cable option is not wanted
pn# M50- 3502042 male pins only need one @ $2.63
pn#M50-3302042 this is an ICD ribbon cable connector that is soldered to main board as option $3.67 an additional idc connector M50-3802042?? is connected to end of ribbon cable. I need to recheck part number.

The four M50-3002045 are soldered to edge of board 2 (has 4 sockets on it)
the male pins M50- 3502042 are plugged into the desired socket on main board .
the M50-3302042 idc ribbon cable connector can be soldered to main board if female connector M50-3002045 is not used
Looking at Mouser

Using this connector I can use 1.27 mm board thickness. Going with 2mm board thickness adds $35 to the cost of boards.
Changing from a 40pin Amtel chip to a 28 pin Amtel chip

[brad]

I just had another thought, could you use the old style ISA connectors like this:



image taken from here:
http://www.cryogenius.com/hardware/isarng/isarng.jpg

[MrDEB]

I looked at similar but using the connectors I indicated, the user can use either ribbon cable or insert similat as your picture.