This post is related to Controlled Impedance Board-to-Board (antenna), but as it’s a new topic I have broken it out to make finding information in the future easier (I generally like one question/topic per thread! reading that thread will provide more context
@ToyBuilder the image you show here (Controlled Impedance Board-to-Board (antenna) - #4 by ToyBuilder) is very close to what I have in mind - though the boar-to-board I was considering was this: https://www.mouser.se/ProductDetail/Hirose-Connector/BM57B0.6-10DP-2-0.3V51?qs=4ASt3YYao0WJUGAJE2LFmw%3D%3D (I don’t need many pins, likely power, serial and a few GPIO for control signals) - I was taking inspiration from the CM4.
I had a couple of concerns and maybe you can help me out
the CM4 uses two connectors which provides some mechanical stability; in your design you use an edge connector and a retainer; any advice? As I say, I anticipate only needing one connector, and I am looking for as low a profile as possible; maybe use two connectors anyway, get the stability and route some extra functionality? a low profile standoff/retainer?
although I am no where near producing anything, I am looking ahead about things that might be an issue. I anticipate probably having the main board assembled for me, as it will be generic and the part that has the most volume. The module/daughter boards though will vary, so I am thinking I will assemble myself - I was inspired by this short from adafruit on prototype assembly (Adafruit ItsyBitsy RP2040 prototype assembly timelapse - YouTube) and thought to do the same (if i can keep the board to < 30mm x 30mm!) - thinking about assembly order - as the reflow plate will do single sided, if i can keep the vast majority of parts on the top side, then use the reflow plate to solder the top side; then use hot air to reflow the B2B connectors on the bottom side?
again, i was looking at the CM4 for how they route to the connector from the top side, and not sure if i was expecting anything else, but its a LOT of via’s - there must be a ton of work that goes into routing most of that through vias, esp. with signal integrity of high speed lines? Fortunately I am not looking at anything like that at this stage… maybe if i ever get there USB would be something I might look at.