GND terminal for probe attachment, SMD type? - Page 1
Forum section: electronics / projects

author: ebastler
author_rank: Super Contributor
timestamp: June 05, 2024, 05:57:59 am
content: With SMD boards and prototypes, I often struggle to find attachment points for my scope GND clip when bringing up or repairing a board. I would like to make it a habit to include some GND pin/loop/clip (or a few, for larger boards) right in the PCB design.But I have not found a suitable part for SMD use. Not knowing what they are called is part of the problem, I guess... Looking for something small, so it does not take too much room and there is not too much leverage on the solder pads -- but large enough to attach a scope probe's GND clip or two. The footprint should not have any through-holes.If you have used something like this, many thanks for pointing me in the right direction. Bonus points for parts that are in JLCPCB's inventory!

author: Someone
author_rank: Super Contributor
timestamp: June 05, 2024, 06:35:17 am
content: https://www.digikey.com/en/products/filter/test-points/616

author: ebastler
author_rank: Super Contributor
timestamp: June 05, 2024, 07:02:43 am
content: Thank you! I might have thought of that designation...Any idea how LCSC/JLCPCB might call these? I see "PCB welding terminals" there, but the few SMD types I can find are all beefy things with a screw thread.Edit: Ah, found them! Somewhat misleadingly grouped under "Pogo Pin Spring Probe Connectors"... E.g. C5199800 is also available for assembly at JLCPCB.

author: exmadscientist
author_rank: Frequent Contributor
timestamp: June 05, 2024, 12:17:13 pm
content: Be warned that those things are utterly awful, at least the ones I have used, and will rip off the board at the slightest provocation, often taking the whole pad with them. They are generally banned from any design I do because I am sick of dealing with the fallout from their failures. I will consider them for specialized uses, just not general ones. And certainly not scope grounds, which get beat on even more than average.I usually solve this in one of a few ways:Put one of the mounting holes close enough to the edge that you can clip between the hole and the board edge. Make sure the hole barrel is plated with a nice fat pad, ground the lot, and you've got a decent test pad.Use a through-hole test point, because my board has through-hole parts on it anyway.Use a through-hole test point, but solder it on myself, because it's easier than dealing with the alternatives.Use a through-hole test point, but solder it with paste-in-pad reflow, so it can go through with the SMD parts in just one pass. This is ideal if my assembler has done this before or is generally easy to work with.

author: ebastler
author_rank: Super Contributor
timestamp: June 05, 2024, 12:54:46 pm
content: Thanks for the warning! Yes, I am a bit weary of the SMD-only mounting too. In the past, I have typically just placed two through-hole pads next to each other and soldered in a U-shaped piece of wire myself, which has worked just fine.But I have played with some designs recently which use the back of the PCB directly as a front panel, hence I want to use SMD only to keep the back side clean. The SMD-only micro USB jacks have held up nicely so far, which lets me hope that the test point will be adequate too. I'll try to place it such that, if it tears off, it does not take any other connections with it...

author: ajb
author_rank: Super Contributor
timestamp: June 05, 2024, 02:58:46 pm
content: Somewhat orthogonal solution, but you can buy replacement ground leads and replace the standard alligator clips with something else of your choice. I have a set with 'dupont' style crimp sockets that will plug directly onto header pins, or onto smaller minigrabbers, which offers some extra options for how you connect to the DUT. That way you're not limited to test points large enough for the alligator clips, or can use a spare header as a grounding point, and don't have to worry as much about the force on a small SMT test point.