How do you test small form factor components out of circuit? - Page 1
Forum section: electronics / repair

author: Traceless
author_rank: Frequent Contributor
timestamp: May 18, 2023, 11:12:38 am
content: If you're working with smaller SMD stuff (e.g. 0201/0402 resistors/caps, SOT-23-X, QFN, SOIC, MSOP, WDFN... etc) you probably know the problem that applying the right amount of pressure with your DMM probes to get a good reading while not shooting the part into orbit is an art. Currently I cheat with sticky tape but that has its limits. I wonder how you deal with this problem?I think it would be nice to have asingletest-board with test points and sockets for the most common footprints. Something like the board in the picture but with testpoints and sockets for everything. The board could have plated throughholes around the edges numbered 1-64 that connect to the matching pins of each socket. Does something like this already exist? One problem I see is that there are probably no sockets/clamps for the most filigree parts like the 0201/042 resistors/caps. I've seen SMD fuse holders but those are usually a lot bigger.Do you have other/better solutions?

author: RoGeorge
author_rank: Super Contributor
timestamp: May 18, 2023, 11:43:50 am
content: Once I've put a Neodymium magnet underneath, so the SMD won't jump.Many parts are slightly ferromagnetic. A strong magnet in a plastic bag (or in cling film) might help keeping the SMD under probes without using sticky tape. Doesn't completely solve the problem, and not a good idea for SMD ferrite coils.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 18, 2023, 11:52:07 am
content: for smt like this you have dedicated tweezers for thatspring loaded fixtures too, forget the price lollexamplehttps://www.itm.com/product/gw-instek-lcr-15-test-fixture

author: Traceless
author_rank: Frequent Contributor
timestamp: May 18, 2023, 12:08:39 pm
content: @RoGeorge: Nice trick with the magnet =). And probably even better than the sticky tape solution.@coromonadalix: Those fixtures look nice - I found aless expensive one, but its not exactly cheap either

author: coromonadalix
author_rank: Super Contributor
timestamp: May 18, 2023, 01:26:03 pm
content: but if you're good in mecanics, you surely can find a way to mimick theses setups at a lesser cost

author: abdulbadii
author_rank: Frequent Contributor
timestamp: May 18, 2023, 03:22:09 pm
content: used customized tiny alligator clip of two or either probe tips, hardly found a satisfactory most suitable one though

author: patrick richardson
author_rank: Newbie
timestamp: May 18, 2023, 04:46:54 pm
content: I sometimes use a piece of painter's tape-- set it on the sticky side to keep it from moving around. The good quality blue painter's tape doesn't leave residue.It's not great, but can help.

author: exe
author_rank: Unknown
timestamp: May 18, 2023, 05:52:16 pm
content: For sot-23 I have a a zif socket (PCA23).

author: Gazza2
author_rank: Contributor
timestamp: May 19, 2023, 08:08:36 am
content: I keep a small blob of Blu tack on my bench for holding surface mount components while testing with probes.

author: ebastler
author_rank: Super Contributor
timestamp: May 19, 2023, 09:07:51 am
content: If you have a bit of spare budget, dedicated LCR tweezers are a great addition to your toolkit. Also nice for measuring in-circuit! (Single-handed, and with low voltage which helps to get valid results without getting semiconductors involved.)There is a recent product from a small (one-man?) company which was developed with a lot of input from this forum. Precise mechanical design and very good measurement performance, and relatively affordable:https://www.eevblog.com/forum/testgear/design-a-new-precision-lcr-tweezers/.They are sold via AliExpress as "ST42".

author: Traceless
author_rank: Frequent Contributor
timestamp: May 19, 2023, 11:10:02 am
content: Quote from: patrick richardson on May 18, 2023, 04:46:54 pm@patrick richardson: Sticky tape was my go-to solution as well (I usually use the clear type). The biggest downside is: with decreasing component size the surface area decreases and so does the effect of the sticky tape.@Gazza2: Nice idea with the blu tack I think that might work better than tape, especially for the tiny components because you can push them into the mass.@ebastler: I actually do own LCR tweezers but they arewayto big for the components. Below is a picture of an IC a capacitor, the tweezers and my DMM probes. LCR tweezers only solve part of the problem - for testing IC's I need to be able to perform diode mode measurements which won't work with the LCR tweezers of course.

author: ebastler
author_rank: Super Contributor
timestamp: May 19, 2023, 11:37:51 am
content: Quote from: Traceless on May 19, 2023, 11:10:02 amAh -- the ST42 are much more slender than that. The whole unit is self-contained (with electronics, display and LiPo battery on board) and sits in your hand like a pair of conventional tweezers. And they come with fine, pointed tips. Easily good enough for measuring 0402 etc., and smaller with a bit of care and magnification. The website has a few photos and videos to give you an idea:https://shannontweezers.top/docs/introduction/While they are categorized as "LCR tweezers", they do support diode testing, including an LED test mode up to 2.38 V. No voltage (let alone current) measurement mode though.No affiliation, just a happy user here.

author: Traceless
author_rank: Frequent Contributor
timestamp: May 20, 2023, 08:21:18 am
content: Quote from: ebastler on May 19, 2023, 11:37:51 amThe tweezers look nice and definitly have finer tips than mine. Also the additional diode test is a pretty unusual feature for an LCR meter.

author: RoGeorge
author_rank: Super Contributor
timestamp: May 20, 2023, 08:33:37 am
content: For new components, should be easy to make golden plated footprints on a PCB, then to press the part from above with some rubbery/putty like, or some gel in a ziplock plastic bag (so the gel would take the shape of the chip + pins when pressed from above).Speculating on the same idea, maybe a rubbery baloon-like foil from above, plus holes in the PCB and vacuum from below (with a syringe piston, or some other manually operated pump). That might work as an universal socket for almost any SMD part, as long as there is a PCB with the right footprint.

author: tautech
author_rank: Super Contributor
timestamp: May 20, 2023, 09:01:16 am
content: Quote from: Traceless on May 20, 2023, 08:21:18 amNot so.ST42 tweezers have been designed around industry smart standard tweezers that have been industry standard for nearly 2 decades. While I don't own ST42 tweezers yet should something happen to my now quite old ST3 they would replace them.