Are there any test probe/connector options for plated through holes in PCB's? - Page 1
Forum section: electronics / general

author: Refrigerator
author_rank: Super Contributor
timestamp: May 14, 2024, 11:16:04 am
content: Hey guys i've been playing around with PCB's and for a while i used to make my own probes for plated through holes (see attached pic).Making them is quite tedious and requires that i have that one special floppy drive connector to pull the contacts from.So i started wondering if there are any off the shelf connectors that i could perhaps use?From what i've found there are insertable (or solderless) connectors, but they're mostly single use and deform both the PCB and the pin itself upon insertion, while some are non-removable at all.What i'm looking for is a probe that can obtain a good mechanical connection to the plated through hole without damaging the PCB.Pogo pins are also not an option because i don't have anything to hold them down onto the plated hole to keep them secured.I've seen some japanese manufacturers who can custom make connectors that are re-insertable for up to 40 times IIRC, basically what i'm looking for but they're custom order items.Would appreciate any pointers to the right direction, assuming that what i'm looking for even exists.

author: Psi
author_rank: Super Contributor
timestamp: May 14, 2024, 11:37:16 am
content: The hard bit is finding what they are called.But seems extremely likely they do exist.

author: Refrigerator
author_rank: Super Contributor
timestamp: May 14, 2024, 12:21:16 pm
content: Quote from: Psi on May 14, 2024, 11:37:16 amYes exactly this, because when i searched for them it sometimes seemed like i've seen everything but then i find another keyword and it's like it opens a whole new chapter of search results.I also expect there to be something because it seems like such an easy and convenient way to connect to existing through holes that surely there has to be someone who has already made probes for it.

author: Psi
author_rank: Super Contributor
timestamp: May 14, 2024, 12:39:04 pm
content: I imagine they will probably be constructed with a cylinder inside two half-cylinders with a spring on the top.The spring forces the pin down a channel between the two half-cylinders expanding the overall diameter and locking the thing inside the TH.But you can release them and the pin retracts reducing the diameter so you can remove them from the TH.That's what i'm thinking anyway.

author: Refrigerator
author_rank: Super Contributor
timestamp: May 14, 2024, 12:59:31 pm
content: Quote from: Psi on May 14, 2024, 12:39:04 pmThat's along the lines of what i was thinking also. Some ZIF solution, like one of those clip-on probes that hook on pins, but for holes.

author: Refrigerator
author_rank: Super Contributor
timestamp: May 14, 2024, 01:09:20 pm
content: To iterate, here's what i was thinking of for a probe tip.

author: Ian.M
author_rank: Super Contributor
timestamp: May 14, 2024, 02:06:53 pm
content: Don't over-complicate it! You can get brass split pins all the way down to 0.8mm dia. Bend one leg in a little half way down to add some outwards spring pressure, and solder your wire to the eye, legs up, with a slip of paper between them to stop the solder wicking up and fusing the legs together.

author: selcuk
author_rank: Frequent Contributor
timestamp: May 14, 2024, 02:22:07 pm
content: What you want is similar to a snap in ( or snap lock ? ) nylon distance. It should be conductive for sure. You may search with those words.This site has variety of test pins for other options:https://www.toby.co.uk/pcb-hardware/test-points-and-pins/You may consider using pogo pins again since they are useful for testing boards via unsoldered header pin pads and without damaging the PCB. Attached photo is an example test setup I use.

author: ajb
author_rank: Super Contributor
timestamp: May 14, 2024, 03:08:38 pm
content: For three or more pins in a row, I've had good results by using regular header pins and kinking the pins in alternate directions. Basically bending each pin in one direction at the base, and then the same amount in the opposite direction halfway up the pin. Ideally the tips of all of the pins would end up back in line after both bends. The amount of bend required depends on hole diameter vs pin size, so may take some tweaking.

author: thm_w
author_rank: Super Contributor
timestamp: May 14, 2024, 09:58:06 pm
content: I feel like press fit would work, just either don't insert it all the way or get a type that is more flexible.https://www.i-pex.com/product/isfitDoubt they will be cheap.The other option, for less connections, can be pcbite style arm with pogo pin tip. The stock ones are too small for standard size pogos but you could make your own larger size.

author: Someone
author_rank: Super Contributor
timestamp: May 14, 2024, 10:14:07 pm
content: Press fit pins are ok for this, such as TE Connectivity AMP 3-928776-4But you need them in different sizes and they don't have a long life.

author: srb1954
author_rank: Super Contributor
timestamp: May 14, 2024, 10:45:39 pm
content: Quote from: Refrigerator on May 14, 2024, 12:21:16 pmSearch for "board-in" connectors (e.g. Molex 50034) series contacts. These are springy contacts designed to hold a loose wire in place in a PCB hole prior to soldering - they not intended as test probes but might suffice for your purposes.They are intended for one-time usage so the contacts are just tin-plated and the contact quality will degrade after multiple insertion cycles but they are cheap enough to be replaced (providing you have the correct crimping tool) on a regular basis.

author: tooki
author_rank: Super Contributor
timestamp: May 16, 2024, 05:58:47 pm
content: It does exist:https://e-z-hook.com/test-hooks/micro-hook/xg25/https://e-z-hook.com/test-hooks/micro-hook/xg31/https://e-z-hook.com/test-hooks/micro-hook/xg40/It’s amazing that in all the threads asking for these things (both eevblog and elsewhere), nobody has ever mentioned these.

author: thm_w
author_rank: Super Contributor
timestamp: May 16, 2024, 10:18:48 pm
content: Quote from: tooki on May 16, 2024, 05:58:47 pmHave you used one? The tolerance specs are quite tight (0.031 to 0.033" holes).Digikey just has the one model for $7/ea:https://www.digikey.ca/en/products/detail/e-z-hook/XG40RED/1965884

author: tooki
author_rank: Super Contributor
timestamp: May 17, 2024, 09:20:57 am
content: No, I haven’t. Sorta on my wish list.The tight tolerance is why there are three sizes.

author: ajb
author_rank: Super Contributor
timestamp: May 17, 2024, 04:02:24 pm
content: Taking the spring out of this style of grabber and keeping the cap compressed to expose the tabs seems to work alright on ~1mm holes. There's no positive lock, and you'd have to be careful to not snag and damage the exposed metal prongs, but they're cheap and widely available (you probably already have some!). Actually slightly higher quality ones with thicker prongs seem notably better. You could probably reshape the prongs a bit to make them easier to insert.