Hello all. I originally posted this to the RPi subreddit but didn't get any response. If this is not appropriate for here, please let me know and I'll delete it.
I'm working on a project that has two standard-size hats stacked on an RPi4. I'm having them made and assembled at a well-known PCBA fabhouse. So far for my prototypes, I've soldered on the female 2x20 headers to the bottoms of both the boards (I know you can specify fabhouse to do this, but I haven't yet).
So, the problem I'm having is I solder the lower board headers to the PCB, and I'm super careful to use as little solder as possible, so the second hat can stack on top of it. But it doesn't work -- the through-hole pins on top of the female headers (that pass through the lower board and are soldered) just aren't long enough to make full robust contact with the secondary hat female headers. This is about good as I can get -- which is totally janky:
I've tried the longer "stacking" headers, but the male pins are just way too long and the secondary hat won't seat fully (see photos) even if I cut the longer pins short, the solder still wicks up and gets in the way.
What I'd like is to use what some of these professionally made boards have -- which is SMT for both the female headers on the bottom, and the set of male headers pins on the top, also SMT. See the photo below of a commercial GPIO expansion board -- this is what I need!
So will this work (See below)? I would PCBA the male TH pins on the top layer, and manually SMT/hot air solder the bottom female pins at home. I want to avoid getting into the "Standard" double sided PCBA, I'd like to stay on single-sided "Economy" PCBA.
On Top: C5224014 Standard male THT header pins
On Bottom: C5423443 -- female SMT header -- this part has dual-entry holes which looks like it allows for the lower pins to slot into - but possibly not an electrical connection, which is fine, both parts are routed to each other.
The last photo below shows how the plated through holes for the top layer male pins line up perfectly with the copper pads for the female header on the bottom side (not assembled at the fabhouse).
Is this good, or is there a better way?
thanks.
