Fixtures/Mechanisms for postitioning and holding probes, soldering irons, etc? - Page 1
Forum section: electronics / projects

author: incf
author_rank: Frequent Contributor
timestamp: March 26, 2025, 01:55:27 am
content: Sometimes, you have a high value prototype with tiny components that you want to do various R&D type operations to, for example:precisely/reliably holding multiple probes on tiny pins (think sharp pointed probe on QFN pin/pads)carefully soldering 32AWG wire on tiny pads and pins (also think QFN pin/pads)carefully cutting or grinding external traces and soldermask on boards with high layer countsAnd the operation (for example holding 5x probes at the same time) are not feasible to do by hand. And adding test points is not an option, etc. And you have to do it yourself rather than trying to farm it out to technicians, etc.In the IC world, they've got fancy probing and positioning equipment for this sort of task. Does anything like that exist for PCB work?Or rather, are there any common ways of doing something similar that are a step up from using "a helping hand" type contraptions. I find myself wishing I could hold probes, soldering irons, etc. in mid air and then finely position them (X-Y-Z) to a certain location and to apply a certain amount of force by turning knobs on a mechanism of some sort.In the machining world ball jointed arms exist for holding dial indicators. I feel like something similar must exist for holding probes onto PCB pads, or for holding soldering irons/wire/etc. The one thing that ball-jointed indicator arms lack is a means of finely positioning or manipulating something like a probe to get it lined up on a 0.4mm pitch pad, or to apply a certain amount of pressure while trying to make contact.I'm sure some will say "just do it by hand" or "just get someone else to do it" - but I don't think that approach is feasible in my particular situation.

author: scottapotamas
author_rank: Regular Contributor
timestamp: March 26, 2025, 06:37:45 am
content: For electrical probing, the PCBite (Sensepeek) magnetic plate with clamping posts is a pretty good approach, there's a range of spring probes for power supply, basic DMM/logic, and a range of scope probes.I've had no issue with this approach for probing around HDI boards, 0402 is pretty easy, smaller DFN and 0201 scale parts can take a few tries to get proper contact.Some of the test equipment manufacturers have their own approaches for holding a browser probe on a trace etc.For the more mechanical side, you might be able to get some ideas from the ecosystems of mounting/alignment fixtures for optics bench work - lots of cool clamps, kinematic stages, alignment mounts.Not usually that affordable though.Might be some tooling for jewelers, watchmaking that could also be adapted?

author: incf
author_rank: Frequent Contributor
timestamp: March 26, 2025, 06:46:03 pm
content: Quote from: scottapotamas on March 26, 2025, 06:37:45 amAre those spring probes made from a pogo pin? I'm not sure which line of probes you are referring to.

author: Ice-Tea
author_rank: Super Contributor
timestamp: March 26, 2025, 06:54:11 pm
content: Yep, pogo pins.

author: woody
author_rank: Frequent Contributor
timestamp: March 26, 2025, 07:08:40 pm
content: Quote from: scottapotamas on March 26, 2025, 06:37:45 amThey really do a good job. Just today I removed a measurement setup from my desk that had two PCbite probes connected to a pcb for more than two weeks. If you align them carefully they stay put. A great solution.

author: Ice-Tea
author_rank: Super Contributor
timestamp: March 26, 2025, 07:31:41 pm
content: Wouldn't mind if they were a bit stiffer, tho...

author: incf
author_rank: Frequent Contributor
timestamp: March 26, 2025, 07:43:17 pm
content: Quote from: Ice-Tea on March 26, 2025, 06:54:11 pmThat system looks great.

author: jpanhalt
author_rank: Super Contributor
timestamp: March 26, 2025, 09:00:45 pm
content: I use Noga dial indicator holders. They allow a very fine screw adjustment and have minimal spring back. That brand is expensive (I got mine years ago), but cheaper versions are widely available. They have mixed reviews, but today, I would certainly research those alternatives.

author: incf
author_rank: Frequent Contributor
timestamp: March 26, 2025, 09:04:00 pm
content: Quote from: jpanhalt on March 26, 2025, 09:00:45 pmAre their probes that can be gripped by a dial indicator holder?

author: jpanhalt
author_rank: Super Contributor
timestamp: March 26, 2025, 09:27:08 pm
content: I don't know per se that such clamps exist. Some of the clamps will clamp something (like a indicator stem) that is about 1/8" (3 mm) diameter, so they can clamp an alligator clip that holds a probe. The smallest thing I have probed is a TQFP.

author: thm_w
author_rank: Super Contributor
timestamp: March 26, 2025, 10:37:57 pm
content: It sounds like you are more asking for a precision x-y table (linear stage), if you want to do precise machining. You should be able to find surplus ones for microscopes, etc.Previous threads:https://www.eevblog.com/forum/blog/pcbite-handsfree-oscilloscope-probe!/https://www.eevblog.com/forum/reviews/pcbite-is-a-brilliant-oscilloscope-probe-holder/https://www.eevblog.com/forum/chat/is-there-a-more-precise-version-of-classic-soldering-helping-hands-tool/https://www.eevblog.com/forum/reviews/a-3rd-hand-that-actually-works!/https://www.amazon.com/SmallRig-Adjustable-Friction-Articulating-Monitor/dp/B087T4T8D5

author: incf
author_rank: Frequent Contributor
timestamp: March 26, 2025, 11:34:43 pm
content: The probing portion looks like a solved problem.For the other half:In the future I think two cheap non-precision XY tables could get me where I wanted to go. (to provide X / Y for PCB and X / Z for the tool)I'd bet that a lot of tools like soldering irons, etc. could be fixtured in sufficiently rigid articulating arm, positioned, and actually be used/useful under that scheme. (it would be tediously slow, but have a low error rate)Perhaps the only part that is missing is a small macro camera that could be freely positioned to inspect 0.5mm pins after soldering / grinding / etc.Probably would have to set up a dedicated PC + monitor just to use a USB macro camera.

author: thm_w
author_rank: Super Contributor
timestamp: March 27, 2025, 12:54:29 am
content: Probably want a smaller table than that, unless its a huge PCB.https://www.youtube.com/shorts/BTVSaPJwVWk

author: Smokey
author_rank: Super Contributor
timestamp: March 27, 2025, 04:53:43 am
content: I'll be that guy.Maybe consider adding accessible test points to your PCB design up front for all signals that will need probing.

author: cunningfellow
author_rank: Regular Contributor
timestamp: March 27, 2025, 10:29:41 pm
content: The board I am working on this morning has 76 test points on it and zero ohm links to isolate different power rails. I designed it.The board I was working on last week had zero test points, unnecessary use of BGA packages (TTSOP version available and no space constraints) and vias coming up under QFN packages going straight to the pin. Someone else designed it and is asking me to fix it.So that is one reason to not just use test pointsBTW - I use Kynar wire wrap wire soldered to pins most of the time as I have never found a good probing method.