DIY SMD Tweezers
I have made a couple SMD tweezers basically based on an online instructible. It works ok but has a habit of the tips snapping and flicking the SMD component somewhere where it could not be found.
Here is my old SMD tweezer. The assembly is similar to the one here but with some more heatshrink sleeving.
And now, I decided to make a new one that should work better.
We start with a cheap set of tweezers.
This is a very abused one as can be seen with the bent tips.
The bent tips are cut off to the desired length using a dremel with a cutting disc.
Cut and sanded to remove the sharp burrs.
The inside surface is roughed up for the next step.
A thin (0.8mm) PCB material is superglued to the inside surface as attachment points for the electrical connections.
The tips are sanded and rounded.
And now we prepare the cable.
I chose to use an RG174 mini coax just because I had some on hand.
The coax is also a good choice when used for measuring capacitance as I found its capacitance does not vary as much when flexing.
A trick I learned online on making a long split on the coax. Pull the inner conductor out of the braid and it makes a neat Y split.
The outer shield retains its neat braid.
Once heatshrink sleeving is put on the braid, a drop of hotmelt glue on the Y junction to keep the second sleeving in place.
Now, the wire ends are attached to the PCB strips.
Some drops of hotmelt glue and heatshrink sleeving for strain relief.
Now we can use it as is or add my improvement.
Two clothes pins are used.
Cut the ends off at about 10mm long. Only the sharp points are needed.
It takes solder easily so it is soldered onto the PCB tips.
This is the tricky part. The tips need to protrude exactly the same length.
It took me a while to get this right.
Make sure to let it cool down between solderings so that the superglue does not melt and lets go of the PCBs.
And then bent so they meet at the tips.
Careful on bending the pins. Too much force in the wrong place could peel the copper foil off or separate the glue.
Once they are aligned perfectly, it can easily pick up and test 0402 SMD parts.
A 5mm LED for size comparison.
With the SMD tweezer plugged to my LC meter and zeroed before picking up the capacitor.
Movement of the cable varies the reading by a few pF and even the capacitance of the tips between open and nearly closed varies a few fractions of a pF.
For sub-pF accuracy, the tips are closed partway about as close as it would be when holding the cap. The meter is zeroed and no movement of the cable if possible. Just enough to pick the component up then read the measurement.
Closing the tips then zeroing in inductance mode, we can measure ferrite beads too.
Here is a new device I partly made this SMD tweezer for.
It is a constant current source with 5mA to 20mA range, open circuit voltage of 12V to 48V useful for testing single LEDs, LED arrays/strings or zener diodes.
A multimeter connected through 2mm jacks to measure the voltage across the DUT (device under test).
I could post a new page about this gadget if there is interest or once I clean it up and make it more presentable.
An 0603 SMD LED being tested.
Measuring the forward voltage of a blue LED at 20mA.
The sharp points means I can even test SMD parts while still in the tape.
And how about randomly poking around my assorted LEDs drawer.
08 Apr 2017:
I kept breaking the tip when it accidentally drops from the workbench I replaced the tip and while testing a bunch of tantalum caps and one blew up and burned the tip, I decided to make a mod to, hopefully, make it stronger.
I left the pins full lenght for extra reach and used the strings as shown in above pic to strenghten the tip mounting and also color code it to which is positive. I wrapped many turns of string to bind the pins to the tweezer body and then applied CA glue to prevent it unraveling and make it even stronger.
Seems to work OK, it does have a habit of springing out and flicking the part off because of the long tips but I can live with that.
The extra reach is useful for probing connector pins when testing.
Page created and copyright R.Quan ©22 Oct 2015.