Is there a tool that allows precise soldering?

Question

I was watching soldering videos and the tools (a soldering iron plus solder wire) seem very primitive. And the precision is terrible, a simple shake can move the tip of the soldering iron very far from the desired place.

Are there any inventions in the past decades that have some kind of tool which combines the soldering iron, solder all in one, thus allowing one to solder in the same way as using a biro or pencil with greater accuracy?

If not, why doesn't someone invent something like this?

Edit:

Comments or answers saying that if I am asking this question it must mean I'm a terrible solderer - because this would be non-constructive and off-topic. [<--By the way these are not my words, they were edited but it is the general gist of what I said]

Answer 1

Would you say that writing on paper is primitive? I doubt you'd hear anyone say "paper and pen? hell nah, lemme grab my tablet" for absolutely everything without giving it any thought.

Hand soldering is not the only way of soldering boards (fortunately for us), and in fact the other methods which appeared later are now very affordable and available. And yet, hand soldering is not dead - that should tell you something.

There are basically three families of soldering techniques which are available to pretty much anyone:

1. Hand soldering, based on a soldering iron (cheapest, in the <50$ range)
2. Hot air soldering, based on a hot-air/rework station (just a tad more investment, in the 75-100$ range)
3. Reflow soldering, based on a reflow oven (a bit more investment still, in the 150-200$ range for pre-owned entry-level ovens)

However, even when you've got all of those, I guarantee you WILL still use your soldering iron.

Not necessarily to assemble or rework surface-mount components (though some prefer to use a soldering iron with the proper "drag-soldering" technique or with fine tips, as long as the footprint's pads are sufficiently long), but you won't beat a soldering iron to assemble through-hole components reliably, or wires. Some through-hole components may be able to withstand the heat load from reflowing, but some (most?) will not, and the paste would be very awkward to place.

Also, most of the time you will require a stencil (that is ordered at an additional cost for every PCB you make) for accurately applying the paste necessary to assembling PCBs using 2 and 3. Instead of applying paste with a syringe it's faster to pop the soldering iron.

When reworking a board, you can't use a reflow oven, and sometimes you will not want to use a hot-air station (e.g. if the minimum required airflow for melting the targeted pads may blow some other components off the board in the angle you have to get in), and in this case the soldering iron comes in handy, too.

Don't you think that with all these use cases, the good ol' iron would have evolved if the operators had felt the need for it?

You would be surprised at how accurate hand soldering can be once you "upgrade your eyes": except for physical handicaps, most of the tremour you get is linked to how challenging your brain finds to resolve where the tip of the soldering iron is compared to where you want to go. It's just too small, an actuator is only as good as its sensor we often say. So get magnifiers, monocles, or if you have the budget, get a microscope. Your brain will be able to compensate for undesired movements when it is able to see them sufficiently well. If both your eyes are able to see, you'll get depth perception as well and you will never again consider hand soldering a thing of the past.

I actually find a soldering iron much more accurate than a hot-air station when dealing with small components such as 0402 or 0603 passives.

I would say that tremour is most experienced when placing the components into the paste applied on the PCB - but even for that, you could makeshift an XYZ table for tremour-free placement, invest in a manual placement machine, or even an automatic pick-and-place machine if you have the wallet.

Finally, about combining soldering iron and solder, I'm sure some company sells those - kind of like MIG welders automatically feed the welding material -, but I wouldn't get those even if they were free. Too bulky, you can't feed solder anywhere else than where your tip is (whereas you are supposed to touch the pad with the solder wire, and heat the pad!), and there would have to be a setting for feed speed which would ruin your assembly when you forget to set it - whereas it's child play to just mindlessly adapt the feeding of the solder between big connectors and small passives.

I worked in big corporations, startups, and medium-size research facilities, and we have always used the three techniques mentioned above pretty much equally. When you throw a stereo microscope into the mix, you will find that more time will be lost somewhere else than using the soldering equipment as-is.

It hasn't improved much over the recent years because it's already converged.

Applying solder paste before reflow soldering (credit) Popping the board out of the reflow oven (credit) Hot air soldering under the microscope (credit) Drag soldering under a microscope with a chisel tipped iron (credit)

Answer 2

the precision is terrible, a simple shake can move the tip of the soldering iron very far from the desired place.

When you need so much precision that your hand can't do the job anymore, you don't hand solder :)

some kind of tool which combines the soldering iron, solder all in one

Yeah, I've had one from Weller in the 80s. It was a gimmick and improved nothing.

Use the right tools for the job: if you need to do precise surface-mount soldering, then you have many options. Just a few are:

1. Use a stencil and reflow.

2. Use a flux pen and a drag method, where a large soldering iron tip is dragged across the miniature pins of chips, and around the leadless dual-in-line and quad packages.

   The flux ensures that no solder bridges form, the large tip ensures that heat is delivered fast enough to prevent bridging. This is a hand-tool equivalent of wave soldering and it works great.

3. Use a glue dispenser to glue the tiny discrete parts down, cure the glue in an oven, and then hand-solder them without worrying about the parts moving around.

4. Use a spring loaded vertical hold-down rod to keep the tiny discrete parts down while you solder them, without glue.

5. Order an assembled board from JLCPCB, PCBWAY, etc. Those are quite affordable even for hobby prototypes.

In a nutshell: hand soldering loose parts being "problematic" (as I imagine you see it) simply doesn't come up when you are aware of tools other than the soldering iron. The problem isn't about having the iron dispense the solder wire - it would also need to dispense the flux, it'd be more like a 3D-printer extruder than a soldering iron. And all that to try and solve a problem that has plenty of miles better solutions. And it doesn't solve shaky hands. Also, not everyone has shaky hands - it varies a lot between individuals, with age, experience and even medications.

I was just wondering why the tools haven't improved in like 20 years. Still people are soldering by hand and breathing in fumes and shaking their hands.

No. Professionals only do that when it's appropriate or isn't a problem. The social media crowd, beyond a few professionals, is largely clueless when it comes to soldering, and makes an impression you got. You can choose to watch better content, that's all.

Sure with practice it's simple enough. But people invented the pen for a reason.

?! Without practice, the pen drawings look like this:

Same goes for soldering. If you haven't got a couple dozen, or better hundreds hours of it under your belt, don't expect miracles - same as you shouldn't expect a toddler who has only had a pen for a few days to be the next Picasso.

Answer 3

Tools

Are there any inventions in the past decades that have some kind of tool which combines the soldering iron, solder all in one, thus allowing one to solder in the same way as using a biro or pencil with greater accuracy?

Yes and no. I'm not aware of any "all-in-one super soldering iron", but many different kinds of specialized tools exist. They're often used in the factory floors for large-scale rework with higher efficiency, reliability, and repeatability (at the expense of extremely high prices).

Specialized Soldering Iron Tips

The simplest forms of "mechanization" of hand soldering are specialized soldering iron tips for particular tasks. For example, tweezers tips are designed for quickly soldering and removing SMD resistors and capacitors. Blade tips greatly simplifies the process of cleaning leftover solder from BGA and QFP footprints after component removal. There are also specialized removal tips designed for SOT, PLCC and J-Lead components.

_{Source: IPC-7711/7721 - Rework, Modification and Repair of Electronic Assemblies}

QFN stencils

Reliably reworking QFNs is often a headache. QFN stencils are probably the most foolproof solution to this problem. These stencils allows one to print solder paste directly onto the QFN components, one can say they're an evolution of the BGA reballing stencils. All you need is a clean pad, the tricky tasks of pre-tinning the PCB, the component, or drag-soldering the pins are avoided.

Two versions exist, one is just a regular metal stencil ordered from your regular SMT manufacturing plate. Another version uses polyimide tapes. These are extremely useful for reworking dual-row QFNs or QFNs with irregular pads, both are very difficult if not impossible for hand soldering.

_{Source: Simple QFN Placement}

Vacuum Desoldering Gun

If you're not already good at soldering, removing large through-hole parts is often accomplished by solder that refuses to leave and destroyed pads - especially if such through-hole has a small size, have a solid connection to the ground plane, or both at the same time. A common multi-layer board problem is that the heat doesn't conduct to the other side, preventing removal. A vacuum desoldering gun allows one to heat the joint and removing solder at the same time thanks to its vacuum pump.

_{Source: Huanyu Electric}

Hot-Air Pencil

Unlike ordinary hot-air guns, hot-air pencils can be described as their precision version. The tip is small enough to heat SMD resistors, capacitors, or component pins individually, minimizing the risk of creating thermal stress to the rest of the board. Useful for small rework, but probably won't work on boards with high thermal capacitance.

_{Source: Zephyrtronics}

Soldering Fountain

Remove large through-hole components such as sockets and connectors are often extremely challenging. The PGA CPU sockets and PCI connectors from older desktop computers are a typical example. A soldering fountain simplifies the removal by spraying molten solder directly onto the circuit board, allowing immediately removal. There are also automatic versions with vision and mechanical positioning.

_{Source: The significance of desoldering and resoldering methods in robotic automated rework, by Necdet Geren, et al.}

Hot Air Rework Systems

Hot Air rework systems are far more powerful than a hot-air gun. They include a microscope vision, bottom pre-heating, positioning, vacuum pickup, and a programmable thermal profile. Today, they're almost mandatory for doing BGA rework. But it's also possible to rework QFNs if you already have one...

The most advanced type (not pictured) can even help you to align and bump QFN and BGA chips semi-automatically at micrometer precision.

_{Source: WDS-620 from Shenzhen Wisdowshow Technology}

Conclusion

Many different kinds of specialized tools exist to mechanize or automate hand soldering and reworking. Most of the tools have existed since the late 1990s, and are part of the standard rework procedure in the industry. Today, their most advanced versions are completely automated.

If not, why doesn't someone invent something like this

There are two problems:

1. Narrow scope. Most of these tools can do only one thing. For example, you need to change the iron tip for each chip you need to rework on. It doesn't make sense to use them unless you need to do the same rework on multiple boards.

2. Extremely high prices. Many of these tools cost up to several thousands dollars. As the main customers of these industrial tools are large companies, there's little motivation for manufacturers to create low-cost versions.

Thus, the use of these tools are limited to the factory floor, they're almost non-existent in small workshops. Perhaps you can create an open source and low-cost design to help the rest of the community?

Finally, some comments

I was watching soldering videos and the tools (a soldering iron plus solder wire) seem very primitive. And the precision is terrible, a simple shake can move the tip of the soldering iron very far from the desired place.

I have to say that I strongly agree with you for several reasons.

First, it's one thing if an expert-level worker can rework a difficult part successfully, it's another thing to do the same rework on 100 boards reliably and consistently in a day. Second, there's an upper limit to pure hand soldering. Some packages and footprints are inherently extremely difficult to solder - such as dual-row QFNs with an inaccessible inner row of pins that cannot be inspected or heated by an iron, there are also QFNs that uses multiple bottom pads with irregular shapes. Finally, better soldering tools will help expert and non-expert alike. For experts, better tools may allow them to do more work within their valuable time. For non-experts, better tools may help them to successfully solder something that they otherwise cannot (so that they can use their time to do something more productive, such as debugging the loop compensation of an opamp or the firmware on a microcontroller, rather than fighting with the pins on an LFCSP package).

Many other answers mentioned the importance of experience - with enough skill, everything is possible - of course, but it misses the point. None of these soldering tools I mentioned are a replacement of training and practicing. All of the specialized tools I mentioned also require training to be used properly (a soldering fountain is not something to be messed with...), the real point is the productive work that can be done when the same time and effort spent on practicing.

Answer 4

Handheld soldering irons are easier to be precise with if they're small and light.

A soldering iron needs to heat the thing you're soldering to, faster than that heat can leave. This means it needs to deliver 10s of watts of heat, and reach a high enough temperature for solder to flow well. The physical size and weight of a power cable or batteries, plus a heating element, plus enough insulation that you don't burn your hand, already makes a soldering iron bigger and more awkward than would be ideal. Adding extra features like automatic solder dispensing then has a drawback, as it's heavier and clumsier - better to put the solder and flux in your other hand.

There are other soldering techniques like reflow/wave which are used for mass manufacturing and are easier to scale and automate. The main advantages of a handheld iron over these are cost, set-up time (making a custom stencil and pasting/reflowing one single component takes ages, grabbing an iron and a spool of solder doesn't), and versatility (you can't use a reflow oven to solder an array of mechanical keyswitches with plastic housings, or to char a pattern into wood). Any modification to the basic soldering iron would make it worse at these advantages (a solder/flux dispenser would make it take longer to set up as you'd have to set the feed rates, and mean you can't use specialist solders or fluxes, and cost more).

So there aren't that many possible ways to improve a soldering iron without big drawbacks, other than generally smaller/lighter and having the handle nearer the tip.