1. Is it realistic to expect this to work?

2. Will the sockets on the Child PCB mate properly with the Main board SMD headers?




I know the sockets will be perfectly flat; they're 90deg and sitting on the PCB surface. I'm worried that the headers might be slightly out of alignment and cause mating problems.

I prefer to use separate headers for each function of the child board (if at all possible). Also, excessively long sockets are not easily accessible.

 

You're right, it will be likely out of alignment and cause mating problems unless you use a soldering jig of the mating connection to force precise alignment between board headers. IMO that's a poor electrical and mechanical design.

 

Correct. Avoid mating boards with headers. Use ribbon cables instead.

 

I'm looking for vertical card connectors, but JLCPCB doesn't seem to have much choice. They do have this 100P Edge Connector.


My longest Child circuit has 55 contacts. I could flip the last 5 contacts on the back side and use this.

I've never done edge fingers (or whatever they're called), do you have any advice?

 

You're right...

I hate it when that happens.

...it will be likely out of alignment and cause mating problems unless you use a soldering jig of the mating connection to force precise alignment between board headers....

I just would have used the Child circuit as an "alignment tool", but the assembly will be done overseas.

.... IMO that's a poor electrical and mechanical design.

Yeah, I was afraid that was the case. I "might" lay the Child circuits flat under the Main board and use ribbon cables, but I'm looking at a card edge connection to start.

 

The worst thing you can do is have two connectors at right angles and the two PCBs bolted together. I had to service and trouble shoot a commercial piece of equipment that did this. It was a nightmare. I had to discard the bolts and solder some jumper wires from board to board.

Ideally the daughter board should be allowed to float on the connectors.
IDC ribbon cables is the better interface.

 

The original plan:

The longest daughter boards are placed along the perimeter, so I can screw the top corners against the sides of the enclosures to stop vibration.

I have 4 small ones spread along the middle, that were going to have the top corners screwed against a "bridging bracket".

The whole set-up is meant to be modular, so I can remove and replace any circuit at will; sort of like a PC set-up.

Edge connectors would be the simplest alternative cause it's so simple to install the 7 daughter cards (2 long, 5 short). I'm just concerned with the overall height. The edge connector adds another 7mm.

Flex PCB cables add some complexity along the connection points. I'm set up for 2.54mm single-sided (I can't relocate traces to the back side on the longest daughter).

I had not thought of IDC cables. They might just be the best option cause I can wire my cables lengths myself until I finalize the layout., and I can wire several in a row like my current header set-up.

As I'm typing his, I checked JLCPCB and saw 11cm lengths of FFC cable for $0.05 each. Still got some looking and thinking to do. FFC might be a decent alternative.