Electronics > Manufacturing & Assembly

Mounting a PCB using only surface mount

(1/3) > >>

charliehorse55:
I'm working on a product that requires one side of the PCB to be completely exposed/flat. I can't grab it from the sides, or use any through holes. So, that leaves me with some way of "grabbing" it by the inside surface. I've looked for off the shelf solutions, but haven't found much. All of the "surface mount" fasteners I've found actually require a through hole to sit in.

So far, my best idea is to create a custom SMD footprint for a "welding nut", something like this:



Some rough calculations show it should be more than strong enough, at least initially. Not sure how reliable lead-free solder is long term when exposed to repeated mechanical stress.

Ever seen something like this done before? Is there a better way to do it?

selcuk:
You can check these as alternatives:

https://www.we-online.com/en/components/products/em/redcube_terminals/redcube_smd

T3sl4co1l:
You're looking for PEM nuts:
https://www.pemnet.com/products-overview/products-nuts/
Which, mind, is a trademark, and there are of course equivalent products elsewhere.

Weld nuts would never have enough solder joint -- they might also not be readily solderable (preferably, tin plated). We've been going over this (sort of) here, as it happens, https://www.eevblog.com/forum/mechanical-engineering/mechanically-strongest-solder/ so you may resolve some ideas there (or, have further questions).

Mind, soldered nuts are at best a compromise.  Even if the solder joint itself doesn't fail, the bond to the PCB laminate is generally not very good either.  Actually, depending on direction (shear vs. tension) and history (fatigue, creep), either one may fail, with laminate more likely in tension or peeling, and solder more likely in shear over long time periods or many cycles of loading.  (I think?)

But these numbers pale in comparison to hardware that engages the laminate itself well, like a press-in (in compression, maybe not so much in tension), swage (gets expanded into the laminate), or simple compression (screw into a normal nut or spacer or other flange) joint.  The whole gamut is covered by PEM's catalog, so you should find many ideas there.

Tim

Smokey:
https://www.digikey.com/en/products/detail/w%C3%BCrth-elektronik/7466005R/6643996


QUANTITY UNIT PRICE   EXT PRICE
1 $2.54000   $2.54
10 $2.12100   $21.21
50 $1.85700   $92.85
100 $1.69100   $169.10

M5 screw.... And it's rated for 70A!

Ian.M:
3M VHB tape?

Navigation

[0] Message Index

[#] Next page