28
\$\begingroup\$

When soldering SMD components, the 2-pinned ones (like resistors, capacitors, ...) are the hardest in my opinion.

I started long time ago with the 1206 format. Then scaled down to 0804, 0603 and finally I'm working with the 0402 ones.

I'm facing a new challenge right now. Once I get some flux on my tweezer points (it happens all the time), they get really sticky. This leads to numerous problems.

If I'm really lucky, I grab the part first time right. This means that I grab the part by its middle, and I can move it to the pads for soldering:

enter image description here

Misery starts when I grab it wrong first time. "Wrong" can be many things: I grab it by the side, it's not aligned well to the eventual target, ... Anyway, the moment I want to release, I open my tweezers and the part keeps sticking to either side of the tweezer points.

enter image description here

Has anyone experienced the same problem? What was your solution?

EDIT

Here are some ideas that might inspire you..

  1. Tweezer material or coating

    I've found a pair of tweezers online like this: enter image description here These tweezers features a "Stainless Steel Body" and "Carbon Fibre Tip". Will this tip material help to prevent the stickiness?

    Perhaps you're using tweezers with some special coating?

  2. Super hydrophobic coating

    Maybe this is a bit strange, but did anyone experiment with a "super hydrophobic coating" on its tweezers? I believe this should help to avoid any liquid/flux from sticking to the tweezer points. I've discovered some sprays online (http://www.neverwet.com/) but haven't bought any of them yet. Would they work on a pair of tweezers?

  3. Tweezer form

    To avoid stickiness, would you recommend a very fine tip? Curved or not? If curved, curved inwards or sideways?

  4. Tweezer tip roughness

    Some tweezers have polished points, others are more rough. What is best?

  5. Demagnetization

    Some tweezers claim to be "antimagnetic". Does this feature really help?

\$\endgroup\$
  • \$\begingroup\$ I sometimes use a pencil to push it down. \$\endgroup\$ – PlasmaHH May 2 '17 at 15:36
  • \$\begingroup\$ Why a pencil? Isn't that too unprecise? \$\endgroup\$ – K.Mulier May 2 '17 at 15:43
  • 1
    \$\begingroup\$ because th is what I have usually lying around? And its tip is usually smaller than the parts... \$\endgroup\$ – PlasmaHH May 2 '17 at 15:45
5
\$\begingroup\$
  • Pick it right the first time

When you un-peel your component tape, the little buggers fall randomly on your work surface. Or more likely, since Murphy's law applies, all resistors fall upside down. Solution is to use double sided adhesive to stick the component tape to something like a piece of cardboard. Then you can pick components from it with your tweezers directly.

  • Clean tweezers

Yeah, the flux sticks... I use a simple sponge, it works...

  • Use vacuum

I haven't tried this yet, but a vacuum pick and place tool is supposed to be amazing for this. Check on youtube for DIY inspiration.

\$\endgroup\$
  • \$\begingroup\$ Thank you @peufeu . I got a few more questions. (1) To clean your tweezers, do you use some chemicals? Perhaps acetone absorbed in your sponge? (2) Do you use special tweezers? Perhaps antimagnetic - if that would help? \$\endgroup\$ – K.Mulier May 2 '17 at 15:49
  • \$\begingroup\$ @K.Mulier Normal IPA (Iso-Propyl Alcohol) should do and is less dangerous to plastics in the vicinity. I put them in the ultraconic after each project (and have a stock of 10+ tweezers of each type), but then I do run a Freelance lab ;-). I also have glass-fiber-plastic tipped range, and they stick as bad, unless components are para magnetic or such. Same for bamboo (mainly for optics). \$\endgroup\$ – Asmyldof May 2 '17 at 15:58
  • \$\begingroup\$ Hi @Asmyldof , you seem to have quite some experience in this! Please hang around a few more minutes.. So if I get this right, (1) You put the tweezers in an "ultrasonic cleaner" each time - do you have a specific one you would recommend?. (2) You have glass-fiber-plastic tipped tweezers. You say they stick "as bad". But which tip do you prefer among all? There has to be one your favourite. (3) You have bamboo tweezers? Isn't that a bit weird? :-) \$\endgroup\$ – K.Mulier May 2 '17 at 16:24
  • \$\begingroup\$ I'm a hobbyist only. But if you use iso (iso-prop, iso-propanol, and odd but I can't recall ever hearing it called IPA when I worked in a chem lab decades back) from a garden variety store, do NOT buy the 70%. I'm not sure about the commonly available 91% because I select and use 99%. But the 91% might be okay. Regardless, do not leave the bottle open (it will absorb water from the air and it's bad enough you had to open the bottle, at all) and add some teflon tape as a thread sealant to help seal the bottle. \$\endgroup\$ – jonk May 2 '17 at 16:27
  • \$\begingroup\$ @K.Mulier Bamboo tweezers are for optics, so you do not scratch them, while bamboo does offer a very good spring force. And they are fun to have laying around when a potential customer comes by. for the ultrasonic cleaner, anything somewhat decent will do. The only difference power makes is the time. The cheapest chinese ones often don't work well (bought 5 to test as "take to customer" devices, all crap), but a small jeweler's one with a few dozen watt of effective power that's somewhat designed should work for small tools. I happen to have several, but again, lab. \$\endgroup\$ – Asmyldof May 2 '17 at 17:49
4
\$\begingroup\$

Yes, there is some inconvenience with that in hand soldering. Yes, tweezers got sticky due to flux, and you can't keep them clean all the time. My solution:

First put a small blob of solder on ONE SMT pad. Leave the other pad clean (or even you might need to wick the solder up)

Then get the part on right side, maybe with a help of another sharp object.

Then get the part to that pad, and solder this ONE END while aligning the part.

Once soldered, the tweezer will unstick easily.

Then solder the second end of SMT part.

If the part gets misaligned substantially, I use a lot of flux and a hot-air pencil, so the surface tension of solder will put the part into right place automatically.

\$\endgroup\$
  • \$\begingroup\$ Thank you Ali. In fact, this is exactly what I try. Once the part is soldered on one side, the stickyness is no longer an issue. But getting to that point is already quite a challenge.. \$\endgroup\$ – K.Mulier May 2 '17 at 16:19
  • \$\begingroup\$ @K.Mulier, yes, 0402 are small, but sometimes you have to use them. Even 0201. To do the job, I use a 10X cheap stereoscope, and use 0603 parts whenever possible, and 0.1mm conical tip, with 0.010" 63/37 rosin-core solder. \$\endgroup\$ – Ale..chenski May 2 '17 at 17:35
2
\$\begingroup\$

As others have said, you can use a sponge (or a paper towel) with 99% IPA ("rubbing alcohol", "isopropanol", etc.) to clean the flux off of your tweezers.

I solder with an iron and wire solder, using a different technique then others have mentioned. I don't know if it's better, but it works quickly for me with 0402's.

  1. Melt just a little solder onto one of the two pads. If you use too much, it'll make step #3 impossible.
  2. Use tweezers to place the part on the pads. It doesn't have to be perfect.
  3. Use a wood (or bamboo) toothpick to nudge the part into exact position, then
  4. Use the toothpick to hold the part down.
  5. Touch the pre-soldered pad with the iron. The component will settle onto the pad and will be held in place by the solder.
  6. Solder the second pad as usual, with the iron and fresh solder.
  7. Important Reflow the first pad again with flux. Until you do this, that pad may have a cold joint. Usually, to save time, I don't bother applying flux: I just use a little fresh solder and it does the job.

Since I'm not placing the part onto flux, my tweezers seldom get fouled and sticky.

\$\endgroup\$
  • \$\begingroup\$ Thank you @bitsmack! I especially like step 3 and 4. Shoving the part into exact position with a toothpick is something I haven't tried before. Is there a special reason to use a wooden toothpick? Lower probability the part will stick to the wood perhaps? \$\endgroup\$ – K.Mulier May 3 '17 at 5:29
  • \$\begingroup\$ @K.Mulier I like them because they're effective and easily available. They come pre-sharpened and will flex a bit, which makes them comfortable for holding down tiny components. They're non-conductive. And they're so cheap that you just throw them away when they get sticky :) \$\endgroup\$ – bitsmack May 3 '17 at 6:25
  • \$\begingroup\$ This is brilliant! \$\endgroup\$ – K.Mulier May 3 '17 at 7:31
1
\$\begingroup\$

There are two problems that I've ran into:
1) Flux on tweezers (or something else) will make the components stick

Clean off your tweezers with flux cleaner

2) Magnetized tweezers steel in the tweezer gets magnetized

Use a magnetizing tool (usually have a slot for demagnetization) or degauss your tweezers.

\$\endgroup\$
  • \$\begingroup\$ Thank you @laptop2d. Please tell me, which "flux cleaner" do you use exactly? \$\endgroup\$ – K.Mulier May 2 '17 at 18:47
  • \$\begingroup\$ Techspray eline techspray.com/e-line-flux-remover-2 \$\endgroup\$ – Voltage Spike May 2 '17 at 18:51
  • \$\begingroup\$ Super, thank you! \$\endgroup\$ – K.Mulier May 2 '17 at 19:13
0
\$\begingroup\$

When I was Ops Mgr for our own quick-turn SMD prototypes, some assemblers used a microscope, others with good eyes direct by hand.

All parts were in numbered 35mm film containers from numbered BOM and some assemblers would lay out all same parts and then use either use a syringe for paste with hot air low velocity small nozzle or very fine wire solder and tack one end. It all depends on skill level.

They were able to make 10 prototype boards a day with 100 mixed size components.

enter image description here

\$\endgroup\$
0
\$\begingroup\$

NONE of that stuff will help you if you get sticky flux on it.

Pick it up more carefully and your problems should go away- in fact you may lose fewer small parts in the transfer.

Depending on your eyesight, you may need a magnifier overtop of where you are picking the parts as well as a microscope over the soldering point.

The best approach is to tin one pad and slide the part sideways into the pad keeping it flat to the board. Do NOT apply any downward pressure to the other terminal, apply gentle pressure and heat it from the side only with the tip wetted. Use plenty of liquid flux and solder that is the right size. Clean with IPA (eg. MG Chemicals). Be careful, it's quite flammable, and so may be the flux (the below MSDS sheet has a typo- it's actually Health hazard 1, not 2).

enter image description here

I'm afraid that 0402 parts are getting close to the limit of what can be efficiently placed by hand- you may want to consider staying with 0603 parts- they are bigger and sometimes marginally more expensive but for hand placement the cost difference is irrelevant.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.