Comments on: Homebrew SMT Probe Tweezers

By: Keith Neufeld

Keith Neufeld — Fri, 21 Mar 2008 15:55:07 +0000

J Holmes –

Faustian’s PCI card edge comment referred to his comment on an earlier post. Rather than cutting up PCI cards to make tweezers, he uses the 1/20″ edge connector for prototyping SMT packages with 1/20″ lead spacing. Because of that, he’d prefer to sacrifice something else to make tweezers.

By: J Holmes

J Holmes — Fri, 21 Mar 2008 15:26:15 +0000

Excellent idea. Wish I’d thought of it.

Faustian – what did you mean by “PCI card edges are much too valuable since they have a 1/20″ raster – so do many SO packages. Perfect mounts.”? Sorry, but it sounds like on one hand you’re saying not to use them (because they’re *too valuable*?), and then to go ahead and use them because they’re perfect. I’m just not following.

By: james d

james d — Wed, 12 Mar 2008 16:16:49 +0000

Great idea! I love these hands on hacks. I saw another hack on a product I bought the other week. I tried it out and it works a treat! It enables my PSU to fine tune voltages with ease. The link to it is: http://www.rapidonline.com/weblog.aspx?id=49

By: James Stoffel

James Stoffel — Thu, 28 Feb 2008 22:18:45 +0000

Keith – great idea. I am just starting to scrounge SMT components, and will need to measure them. This “tip” will help greatly! J.

By: faustian.spirit

faustian.spirit — Thu, 28 Feb 2008 10:39:20 +0000

Sorry to repeat myself – PCI card edges are much too valuable since they have a 1/20″ raster – so do many SO packages. Perfect mounts.

By: Keith Neufeld

Keith Neufeld — Wed, 27 Feb 2008 15:37:51 +0000

Alexander, you might want to look for an ISA (or even older) card — the wider the card-edge traces, the easier it is to make the tweezer tips.

By: Alexander

Alexander — Wed, 27 Feb 2008 15:03:32 +0000

Nice re-use of materials. I have plenty of PCI cards around so I think I will be making one of these as well.

By: faustian.spirit

faustian.spirit — Wed, 27 Feb 2008 08:57:27 +0000

I did it by taking actual cheap tweezers, sawing out two gold contact fingers from a thick old pcb, and filing the back side of the small pcb pieces into a wedge shape – so they could be cyano-glued into the tips of the tweezers thick end first and soldered to with enough clearance. Add some heatshrink (never. ever. be without some) around the solder joints and tweezer handles, and presto….
you get a blunt front, of course, but the wedges also add some grip on the part….

By: Dave

Dave — Mon, 25 Feb 2008 22:22:24 +0000

It might be better to cut the traces off closer to the Gold fingers and solder the wires down there, rather than soldering the wires where you have. The issue is that your fingers will contribute to the capacitance somewhat, and, depending upon how your grip varies, they may shift the measured value slightly. Note that PC board material has a relatively high dielectric constant. And, if the traces being used have via holes to traces where
your fingers connect, then all sorts of screwy readings may result.

If I were going to do it, I’d probably etch off all of the traces more than about a half inch from the Gold fingers, leaving smooth, unplated board for the finger holds.

Oh, of course, I tend to deal with much smaller capacitor values usually, so maybe I’m hypersensitized to this (few dozen pF, rather than .1 uFs)

Anyway, it’s a neat idea.

Dave

By: David Fowler

David Fowler — Sun, 24 Feb 2008 22:53:18 +0000

Very nice problem solving. I need to build one of these to check out a ton of SMT parts I have scrounged. I usualy skip the caps becase they are too much trouble but even so I still have a bunch.