Introduction: I hate connectors. They're big, unreliable, messy, expensive, and introduce crosstalk. If I could put my whole system on one board I would. But when the system is spread across hundreds of meters, or even just involves different circuit board technologies or mix-and-match board sets, I need connectors after all.
The specific need I have at the moment is for a board-to-board connector. The two boards will both be clamped flat to the same aluminum heat sink, so the usual vertical mate board-to-board connectors won't work. I have about 20 low-speed digital lines, some power supplies, and about 12 x 50 Ohm analog RF signals in the 20 to 200 MHz band, where I need low (-80 dB) crosstalk. A set of 10 SMA connectors would sort-of work for the analog RF signals; I want to improve on SMA in terms of cost, density, and assembly time, without giving up much in the way of crosstalk. I hope the low-speed digital and power will come "for free".
I looked at using a single high density connector (Samtec QMS/QFS) but wasn't happy with the amount of board space needed to fan in and fan out. Two or three smaller connectors would work, but if they are high density, I risk reliability due to assembly tolerances putting stress on the contact area. Low density connectors have larger antenna areas, which is bad for crosstalk.
Many connectors I have looked at come close. Maybe I can leverage the current industry excitement about high-speed serial interconnect. I sense that I need a creative way to relax one key spec, but still get the job done.
- Larry
